The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Frame => Topic started by: mikeb on 27.01. 2019 07:27
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My 61 super rocket has the standard 8” full width SLS front brake. I've read lots of brake threads on trying to improve things so I fitted a later floating shoe setup and replaced the old linings as they didn’t make good contact with the drum. The new linings are modern stuff but supposedly a soft material for cable operated vintage car brakes and used successfully on old bikes. The people who did the linings have a good rep down here.
Anyway, after centring the new shoes/linings (by adjusting the fulcrum pin) and doing a few hundred miles they are still pitiful, albeit slightly better than when first fitted. Possibly worse that the original fixed shoes that I swapped out. Photos below show the wear is somewhat more on the inside of the linings and mostly at the ends of the linings - ie the middle of the linings has little proper wear yet suggesting minimal contact. the drum looks ok (to my untrained eye) and feels fairly smooth - I don’t have means to measure the drum.
what to do? Should I get the drum machined in some clever way? Should I try the sandpaper trick (adhered to the drum) to rapidly bed in the new linings? Any thoughts?
Thanks
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Do you know the theory on why it’s important to get the leading shoe to make contact with drum first? I ask as it took me a while to figure it out, but then I had a *woo* moment when I did.
I made a useless 8 inch single sided brake (like the gold star one) go from completely useless to ok just by getting the leading shoe to contact first. There are a couple of ways of doing it but I built up the cam face of the leading shoe by 1 mm.
Using the emery double sided taped to the drum will probably improve things, but unless you put a spacer under the trailing shoe cam face whilst doing it you will end up with the trailing shoe contacting first which may negate any improvement!
My next mod will be to “reverse” the brake lever on the drum.
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Apart from shoe contact, how is the operating arm?
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The brake is wrongly assembled.
The steel pads go at the pivot end.
Service sheet below shows correct assembly.
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Mr Kiwi knows what he’s on about.
If the trailing shoe hits the drum first, it stops the cam from turning, so the cam can’t put any more pressure on the leading shoe.
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I have found easing off the last 1/3rd of the trailing shoe helps quite a bit. This tip has been about for years.
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The brake is wrongly assembled.
The steel pads go at the pivot end.
Service sheet below shows correct assembly.
Unless my eyes are weirder than they were when I woke up, mike's shoes are assembled as in the factory drawing... *conf2*
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No they are not as per factory drawing.
The end of the shoes with the steel pads in Mikes photo are at the cam end. The factory drawing shows them at the pivot end.
First photo is A10 8 inch front fitted with floating shoes.
Second shows the pads on floating shoes, they are not flat, you can imagine the problem of a cam opening on that shape shoe end. You can see the pivot marking on them.
Left is Triumph type and right is BSA type.
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A quick reassemble as Julian has indicated will certainly improve matters. Here are a few other things to consider on any cam operated brake.
Relieving the cam end of the trailing shoe lining will allow the leading shoe to have a bit more pressure as the cam can continue to turn, as T T says. Mugwump suggests 1/3 of the length, so start off gently and see how it goes.
The drum operating lever should be set so that it never passes over the 90 degree angle with the cable. Make sure there is no stretch in the outer cable, as this is is wasted effort. Worth checking you also have the correct handlebar lever, as regards mechanical advantage. Make sure the floating pivot is set up to work as intended, either fully floating or locked in place with the brake applied and the shoes centred, depending on type.
Once full contact is achieved, by bedding in, sanding off high spots etc, the poor performance can only be the retarding properties of the friction lining material.
Swarfy.
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What's this then ?
(https://www.a7a10.net/forum/index.php?action=dlattach;topic=13886.0;attach=46165;image)
And where did this come from..?...;
(https://www.a7a10.net/forum/index.php?action=dlattach;topic=13886.0;attach=46171;image)
To me the drawing sure looks the same as mikes
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Not quite sure what you mean duTch.
The steel pads on Mikes photo are clearly at the cam end. His top shoe in photo needs to be fitted on the bottom side putting the pads at the right end. The linings will still be in the same asymetric position. The shoes are not interchangable, one is made a leading and one as trailing.
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What I mean is that mikes appear to me to be the same as in the factory diagram you posted;
(https://www.a7a10.net/forum/index.php?action=dlattach;topic=13886.0;attach=46169;image)
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On any drum brake with linings fitted asymetricaly, in other words more to one end of the shoe, just imagine that the rotating drum has pushed the lining along to the end. Works every time for assembling them correctly. The start of the lining will be some way from the cam on the leading shoe. Slight sanding to remove the front sharp edge of this leading shoe lining will minimise grabbing.
The factory diagram would indicate cam at the bottom, pivot at the top. Steel pads fitted pivot end of the shoes. You can see how the rotation appears to have "moved" the linings along the shoes.
Mike's shoes just need to be rotated 180 degrees to put the steel pads at the pivot end. The linings will then be in their correct leading and trailing positions.
Swarfy.
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Perhaps this helps.
The pads will only fit on one end of the shoe due to diffrent dimensions.
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yeah ok wahever- I really don't care so much, nought to do with me anyway- was just saying it didn't look right, but at 1:40am before some suds not much does....i had the same issue on my Gutzzi 20 yrs ago and sorted that similar, so probs the same stuff....
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'why is my front brake still useless'. Because they are.
In my experience the FW 8" brake is no better than the SS 7" and nowhere near as good as the SS 8"
I fitted a Triumph TLS backplate to my A10 to try to improve matters, and it's still useless. Modern brake lining materials don't help either - can't beat the old woven asbestos ones. On one of my bikes I converted the SS 8" to TLS and it'll bottom the forks. Wish I could say the same on my A10 with the Triumph TLS.
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thanks for all your comments guys - super helpful.
RD - some guys race with SLS shoes and claim its all in the setup, so while they'll never match the brembos on my modern they can surely get better than what i have.
Julian - your eagle eye was right - i've got the steel pads at the wrong end... arrg! so i'll fix that. i'm endlessly impressed by your cache of service sheets
GB/swarfy - the drum lever is set about right and the handle bar lever is the narrower 7/8 radius type for leverage. the cable is fairy new and without cracks/breaks etc tho has one slight kink in it.
Kiwi/others - I get the point about the leading shoe needing to make first contact. the bike has the lugs on the brake plate that fits to the forks peg so reversing the drum lever is not trivial (i did that mod on my b33). so whats the wisdom on these two methods:
1. building up the cam face on the leading shoe side - how to do that?
2. getting out the file or sanding block to shape down the first third of the trailing shoe?
Also - re 'fitting' the linings:
3. is there merit in fixing sandpaper to the drum and ?going for a slow ride? to bed them in? or just let it wear in eventually?
AND
4. there are some suggestion around to leave the pivot slightly lose to allow some self-adjustment, as well as with the floating / steel plates. is this a good idea?
thanks again
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thanks for all your comments guys - super helpful.
RD - some guys race with SLS shoes and claim its all in the setup, so while they'll never match the brembos on my modern they can surely get better than what i have.
Julian - your eagle eye was right - i've got the steel pads at the wrong end... arrg! so i'll fix that. i'm endlessly impressed by your cache of service sheets
GB/swarfy - the drum lever is set about right and the handle bar lever is the narrower 7/8 radius type for leverage. the cable is fairy new and without cracks/breaks etc tho has one slight kink in it.
Kiwi/others - I get the point about the leading shoe needing to make first contact. the bike has the lugs on the brake plate that fits to the forks peg so reversing the drum lever is not trivial (i did that mod on my b33). so whats the wisdom on these two methods:
1. building up the cam face on the leading shoe side - how to do that?
2. getting out the file or sanding block to shape down the first third of the trailing shoe?
Also - re 'fitting' the linings:
3. is there merit in fixing sandpaper to the drum and ?going for a slow ride? to bed them in? or just let it wear in eventually?
AND
4. there are some suggestion around to leave the pivot slightly lose to allow some self-adjustment, as well as with the floating / steel plates. is this a good idea?
thanks again
On point 4 this I think has the effect of evening out the force on each shoe, which is not what you want in my experience.
On point 1 the shoes I have are alloy with a steel cap for the cam face (are they all like that?), I used a mig to build it up then filed it flat. The difference was amazing, but of course as the leading shoe wears i guess it returns back to rubbish. Reversing the drum lever is the permanent solution to that, reducing the trailing shoe contact area may also help keep the brake good, but I’ve not tried that.
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thanks for all your comments guys - super helpful.
RD - some guys race with SLS shoes and claim its all in the setup, so while they'll never match the brembos on my modern they can surely get better than what i have.
Julian - your eagle eye was right - i've got the steel pads at the wrong end... arrg! so i'll fix that. i'm endlessly impressed by your cache of service sheets
GB/swarfy - the drum lever is set about right and the handle bar lever is the narrower 7/8 radius type for leverage. the cable is fairy new and without cracks/breaks etc tho has one slight kink in it.
Kiwi/others - I get the point about the leading shoe needing to make first contact. the bike has the lugs on the brake plate that fits to the forks peg so reversing the drum lever is not trivial (i did that mod on my b33). so whats the wisdom on these two methods:
1. building up the cam face on the leading shoe side - how to do that?
2. getting out the file or sanding block to shape down the first third of the trailing shoe?
Also - re 'fitting' the linings:
3. is there merit in fixing sandpaper to the drum and ?going for a slow ride? to bed them in? or just let it wear in eventually?
AND
4. there are some suggestion around to leave the pivot slightly lose to allow some self-adjustment, as well as with the floating / steel plates. is this a good idea?
thanks again
I would not put sandpaper on the drum then go for a slow ride. This would likely wear out the shoes completely in one short ride.
Even when manually turning the brake plate with sandpaper stuck to the drum you need to be careful to only take off what is needed, nothing more. The sandpaper or emery does work well for this, however.
I start by sticking it on other way around, that is, stuck to the shoes. Use a clamp to move the brake arm ( wheel off ) to a position where the emery just barely contacts the drum. If , as you rotate the brake plate against drum, you encounter uneven friction ( pulsation) then keep rotating the brake plate against the stationary wheel while gradually and incrementally using the clamp on the brake arm to open the shoes up.
When you have an even drag all the way around, the drum is round. It might take an hour or so and you might have to change the paper a few times.
If you find you have even drag right at the start, then the drum is already round and you can't improve it, move on to arcing the shoes to the drum.
Stick some new emery on other way around, onto the drum this time ( all the way around). Now rotate the brake plate while engaging the shoes as before. This won't take much, 120 grit will remove the high spots on the shoes with very little effort.
After this treatment my 2ls will lock the wheel on pavement and is completely smooth in operation, no pulsation.
Your 1 ls might not be quite that good, but it should be decent.
Glen
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I located the steel pads at the pivot ends and tightened the pivot once centring the shoes (usual routine). then reversed the brake arm – actually not too hard as I previously had made a longer arm so just made a small extension bracket that then offsets the cable by 1/8" closer to the hub. There’s a similar example on a brtibike thread for an a65. See pics below – the cable just clears the forks by a 1/16" or so. Other than looking ugly can you see any problems arising? So now the leading shoe engages first.
I also took Glens tips on sanding the drum (a little tentatively) and linings (maybe a little too much) using strips cut from stick-on sanding discs.
And guess what? From a quick test ride it’s still rubbish. *sad2* Well, better than it was but not good. No chance of skidding the front wheel or stoppies.
Only one thing more to try of loosening the pivot to see it some movement there helps.
Any other thoughts?
thanks
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OK, it looks a bit strange, but an arrangement like that scares me!!
I would return it to standard, and make a thin sheet steel packing pad to go between the cam and the leading shoe. This means the trailing shoe will not hit the drum before the leading shoe, so you can get an idea of how effective the brake is with one shoe doing the work. This is easier than building up cams on one side. Treat this as an experiment, ride carefully. If this appears successful, thin down your pad bit by bit to bring more of the trailing shoe into play.
As set up the leading shoe is the one on the underside of the drum, towards the rear of the machine. Make sure the shoes are fitted with the linings in the correct orientation, as outlined above.
Swarfy.
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Thanks for the heads up about the steel shoe against the pivot, been doing it wrong for 45 years...never ever goin' to stop learning! Cheers.
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The steel pad on the pivot is for floating shoes only.
The 190mm and half width hubs have a flat steel pad at the cam end.
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If this appears successful, thin down your pad bit by bit to bring more of the trailing shoe into play.
Wow, Swarfy, that's a lot of assembly/disassembly you've described in this iterative process. I suppose ultimate safety is the justification, but I'm guessing most of us would say, "that'll have to be good enough" after a couple of rounds of testing. Maybe I'm just old, lazy and busy.
Richard L.
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The steel pad on the pivot is for floating shoes only.
Here's a diagram I captured from somewhere at sometime showing floating shoes correctly fitted and a good explanation of how they work.
And also a photo of my non floating front brake on my 1960 Golden Flash (no steel pads).
(Edit): I can say I don't have a problem with my GF's brakes so I can't complain about their lack of efficiency. Seems it could all be down to lining material.
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Apologies to those who may have misunderstood the finer detail of my earlier post.
By returning to standard, I meant assembling the shoes with the concave pads on the pivot end, as outlined by Julian. Then fabricating an additional thin flat steel pad to go between the cam and the leading shoe, to move the leading shoe nearer the drum so that it contacts the drum first. Then experimenting with the thickness of this pad to try to improve the performance of the trailing shoe.
Maybe just easier to source a late A65 TLS front wheel.
Swarfy.
Additional....RogerSB has an ideal front brake testing facility on the southern approach road to the charming village of Widecombe in the Moor, South Devon...... the incline featured in a popular song, back in the day.
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RogerSB has an ideal front brake testing facility on the southern approach road to the charming village of Widecombe in the Moor, South Devon...... the incline featured in a popular song, back in the day.
Yes, we have lots of narrow, steep windy roads here in the South West of England. I live on the top of one, which gives me a good view of Dartmoor, just 10 minute ride away, that's where I usually head for when out for a ride. There are some places to avoid but on the whole its a great place for motorcycling.
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I recall stopping at the top of a steep descent on a B road in the Dales. There was a sign at the top the read " Steep hill, 25% grade"
I thought that had to be a misprint but soon realized it was correct. We were two-up with luggage.
To make matters worse, there was a T intersection at the bottom with the stop sign on the B road, the other road a busy through road. If unable to stop at the sign, the next stop was the side of a stone house directly across from the stop sign!
Glen
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Time for a laugh and learn moment.....
In a time when the old bike movement was starting to stir, there was a well respected (according to the Mags ) restorer in Leominster, in the fine county of Herefordshire, UK.
So that's where I sent my front wheel hub with its early single sided brake drum. Weeks passed and I eventually collected a nicely restored wheel, fitted it to the bike and all was good.
Some weeks later, on a Club Run to Shropshire, we descended the long steep hill known as the Long Myndd. Got to the bottom, brake working fine, drum smoking as the powder coated or stove enamelled finish (as we thought) bubbled and popped. From the smell we reckoned it had been painted with oil based house exterior paint. The invoice said "Restore Front Wheel" so I suppose that's what I got. Alas, assuming the finish would be heat proof.
Then we realised the spoke pattern was wrong. So, not feeling that the Man in Leominster would be too inclined to put things right, we sent the wheel to a builder in Coleshill, Birmingham, who refinished the hub with heat proof paint and respoked the wheel, all in a matter of days.
I cannot believe the original restorer actually did the work, but that it was farmed out elsewhere......so it looks as if we both got conned.
So, always specify exactly what you want doing as regards materials and their suitability for intended use. As a choice of finish, powder coating is a relatively thin, quick and durable industrial finish, works very well on new clean smooth metal. But it will show up the slightest imperfection. As it is cured by heat, is it capable of withstanding the heat from a hard used brake?
Swarfy.
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... As it is cured by heat, is it capable of withstanding the heat from a hard used brake?...
I've never been aware of the powder coating on my brake drums suffering from braking heat.
I ask again, are there different powder coating finishes available?
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I recall stopping at the top of a steep descent on a B road in the Dales. There was a sign at the top the read " Steep hill, 25% grade"
Glen
Widecombe Hill (the one Tom's mare collapsed and died on and the one Swarfcut mentioned) is a steep hill (I believe up to 22% in places). I have a friend who lives there and been there a few times. However not on my BSA, always by car.
The comment I'd like to make about our BSAs and brakes is that it may not be prudent or safe (maybe, even cannot) ride a +50 year old British motorcycle like you can a modern one in today's traffic and on faster roads. As always, it's horses for courses.
I owned and rode, as daily transport, a couple of GFs in the mid 60s and well into the 70s and they were very capable transport and could easily hold their own in the traffic and on the roads of the day. In the 80s I bought a new Honda CX500, which had powerful hydraulic twin disc brakes and was shaft driven and was a world apart from the BSA and Matchless I owned (and also rode) during that time (see photo). Today, for me, it's the pleasure of owning and riding a BSA and the very quaintness of it that I enjoy and I ride it with that in mind, maybe that's why I haven't felt the need to complain about its brakes.
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Roger - you're so right. Having ridden modern bikes we then tend to expect the same from our classic ones. Trouble is though, with today's traffic one still needs to be safe and the 'appointment to stop' required with older bikes just doesn't cut it. Maybe it's my mind failing after all these years, but I think classic brakes are generally worse now than they were in the 60's and 70's. I'm sure we used to get brakes working at least reasonably back then, but then we didn't have cardboard masquerading as lining material. Having read of all the mods carried out in this thread (and being in the same situation myself with my GF brakes) I'm even more convinced the problem is today's brake lining material.
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Hi All,
Yes lining material is the key to good brakes
This subject has been raised time and time again *sad2*
I have had good results with a soft non woven lining, its dark grey in colour, unfortunately the shop closed some while ago (Supreme)
Recently a Friend has been getting shoes lined at a local place here in Ireland, they are using material that is the same or similar to Supreme's stuff?? They reline shoes for classic rally cars with it
Talking with him the other day he was filing away some more of the leading shoe edge to make the front brake on his Flash less severe *eek*
I found the pattern floating shoes to be worse than useless *warn*
Get the rear cable, lever angles sorted and the correct thickness linings and the rear brake works well
99.99% of pattern rear cables are SH1T *razz*
John
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....filing away some more of the leading shoe edge to make the front brake on his Flash less severe...
*countdown*
Maybe your friend is a thrill seeker.
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what always strikes me is how the rear brake can lock the wheel but the front feels spongy. maybe its the cable size and length?
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I ask again, are there different powder coating finishes available?
Yes there are, there are different heat ranges and they have powder coat capable of doing heads and barrels
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Swarfy yes that extra arm is between ugly and strange but with split pins should it be scary? Ie, dangerous? I made it as I didn't want to mod and solder the brake cable etc.
I might try marking the drum and shoes with pen/pencil to see how much contact is actually occurring. Any tips on suitable markers that won't then affect the friction surfaces?
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what always strikes me is how the rear brake can lock the wheel but the front feels spongy. maybe its the cable size and length?
The front brake is the more important brake. As a motorcycle instructor and examiner throughout the 1980s for the Royal Automobile Club & Auto Cycle Union and later for the British Motorcycle Federation training schemes we always tought the importance of applying the front brake harder than the rear and just before the rear. This would become most important to do automatically if ever faced with an emergency where there's no time to think about it. This is to avoid skidding and possibly losing control completely. We were not allowed to take riders out on the road until they could perform an emergency stop correctly and under some control. It can be easy to skid the rear but not so easy to skid the front - - - but if banked over and turning you're in big trouble regardless.
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MikeB.... No, from an engineering aspect it is fine. I just get a bit jittery in the irrational belief that the cable will get stuck between the backplate and the fork leg. Sod's Law an'all. Kid's coloured chalks could be used to mark the linings to find the high spots.
Swarfy.
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Hi GB,
His problem was that the front brake was
"Too Good" and tended to lock up on wet or greasy surfaces *eek* *eek* *eek*
John
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Swarfy yes that extra arm is between ugly and strange but with split pins should it be scary? Ie, dangerous? I made it as I didn't want to mod and solder the brake cable etc.
I might try marking the drum and shoes with pen/pencil to see how much contact is actually occurring. Any tips on suitable markers that won't then affect the friction surfaces?
Hi Mike, maybe we’ll be discussing this at the National Rally in a few weeks! I agree with previous comment that it’s worth REALLY making sure the leading shoe contacts first, by adding a temp spacer, or building up the cam face by weld I did. I’ve had good feedback from other riders of my B31 on the front brake as “much better than mine *eek* ”. Including from a gold star owner. It will lock the wheel at slow speeds but is a lighter bike of course.
Its accepted pretty generally that more than 75% of your braking comes from the leading shoe (due to the servo effect) so IMHO that’s what one needs to concentrate on, one thing is I’ve not put much thought into is the effect of reducing the leading shoes contact length, maybe this can increase the servo effect? Is it worth trying? (Noting this reduces lining contact area, but increases pressure on the lining).
My gut feel is that removing the part of the friction lining on the leading shoe, nearest the cam, would increase the servo effect? Can someone confirm that? I’m thinking you need to get closer to the “brake grabbing” effect....albeit if you don’t like that effect you may have to get new shoes....as you can’t replace removed friction material!
I note trailing shoes can also have shoes with reduced lining length, I’m not sure why but probably to try to prevent them wearing in a way that prevents the leading shoe working properly, as there is no significant servo effect on trailing shoes.
Another “variable” is the chamfer on the lining, is the servo effect increased with no chamfer? Anyone know? ( I suspect it’s reduced, as no chamfer can cause bad grabbing).
On lining contact area maximising, it appears trying to get an even contact might be a good thing to do but more a “nice to have” ...I say that as sanding the shoes to get perfect contact only made only a small difference to my brake (albeit it reduced the “sponginess” a great deal), and “physics” says friction is proportional to contact area and pressure so if you increase the area you reduce the pressure and maybe end up no further forward *dunno* . I definitely see advantages in spreading the generated heat over the whole friction lining though, as local overheating of the lining may result in a low friction co efficient. Getting the brake to work well is not simple physics though, as shoes flex, linings compress, brake plates flex, drums flex, all of which affects the evenness of force over the lining, probably making it a bit of a “black art”. A SLS brake is inherently “flawed” as one end moves more than the other!
Accepted wisdom around here is that “soft” linings work best on our brakes, and that modern linings are “hard” to suit higher pressures from hydraulic pistons. I’ve no direct experience of this but I suspect some wassel aftermarket bonded shoes I bought are “hard” hence that’s the cause of my useless rear brake (as well as them being too small in diameter, and so thin sanding them to the correct diameter would make them virtually worn out!).
It’s also occurred to that a old school brake specialist would know how to set up a SLS brake to work well, and make the customer happy, but maybe as the linings wear the trailing shoe gradually comes more into contact and reduces the brakes performance, and the specialists knows that!
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For what it's worth, I bought some shoes for my Plunger rear a couple of years or so ago, and they seem to work fine and has even skidded up sometimes but can't say if they soft or hard....bought from Trojan Classics in Sydney;
http://trojanclassics.com/ (http://trojanclassics.com/)
or eBay shop;
http://www.ebaystores.com.au/TrojanClassicMotorcycles/Control-cables-/_i.html?submit=Search&_fsub=2366346014&_nkw=67-8681&_sid=95114404& (http://www.ebaystores.com.au/TrojanClassicMotorcycles/Control-cables-/_i.html?submit=Search&_fsub=2366346014&_nkw=67-8681&_sid=95114404&)
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For what it's worth, I bought some shoes for my Plunger rear a couple of years or so ago, and they seem to work fine and has even skidded up sometimes but can't say if they soft or hard....bought from Trojan Classics in Sydney;
http://trojanclassics.com/ (http://trojanclassics.com/)
or eBay shop;
http://www.ebaystores.com.au/TrojanClassicMotorcycles/Control-cables-/_i.html?submit=Search&_fsub=2366346014&_nkw=67-8681&_sid=95114404& (http://www.ebaystores.com.au/TrojanClassicMotorcycles/Control-cables-/_i.html?submit=Search&_fsub=2366346014&_nkw=67-8681&_sid=95114404&)
Huh?
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Huh?
which end of those do you fit the steel pads??
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KiwiGF - yes, another 'dark art'. I will be at the rally (for the day ride and dinner) and hopefully on the a10 so we can discuss it further then. my b33 (plunger) with reversed front brake arm stops better than the a10 tho maybe just as its a lighter bike. i rode my modern yesterday after riding the a10 more recently and just about broke my wrists stopping at the first corner. if only...
Roger - unfortunately I've never mastered the gentle riding and do tend to ride the bsa's like moderns. i've enjoyed passing porsches and harleys on my b33 - rather adolescent great fun. the good part is 60mph on my bsa feels like about 140kpm on the modern and you don't even get a speeding ticket!
Swarfy - i share some anxiety about this linkage. messing around with brake mechanisms doesn't sound wise to me, even if it looks 'failsafe'. I posted that pic to see if anyone would freak out so i do appreciate your comments.
i'll have a go with the chalk and see what i find
cheers
Mike
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..Quote
Huh?
which end of those do you fit the steel pads??
R.......
Good point...I didn't even look at it- was just the page that came from hysterical ( intended) and used a an example link.......had to go to work and whack my battery back in so I had basic lights and brake lights...but I didn't notice any porches to race, but probably did go past some hidden behind fences : *smile*
........ i've enjoyed passing porches and harleys on my b33 - ......
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good catch dutch. my germanic isn't what it could be. but i hate how porches hide behind fences, and hedges
the b33 passed an audi once too! (memorable as may never happen again)
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Mikeb.....I reckon the rest of the crew wondered why you had done it, but were too polite or unaware of the true mode of action of leading and trailing shoes. The leading shoe is always the same, and is leading or trailing depending on the direction of rotation of the wheel. Assuming the cam is symmetrical, it does not matter which way it moves , so the lever can be fitted either way and the braking will be the same. The 8 point squares in the lever end are slightly offset, so reversing the lever by simply turning it over can move the lever/cam to give a more acute angle to the cable, and a bit more leverage. So, go back to standard and position the lever so it approaches (but does not pass through) the magic 90 degrees at full braking effort.
Swarfy.
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Swarfy – sure the leading and trailing shoes remain what they are (unless going backwards). But are you saying that rotating the arm one direction and not the other makes no difference to which shoe touches the drum first?
My understanding from many threads and from drawing it out is the reversed cam rotation pushes the leading shoe into drum contact just before the trailing shoe – I’m sure you know the theory (triangles etc). as per why velos ran the brake on the other side of the wheel and racing bsa’s often reversed their front lever rotation. So that’s why I reversed it… leading shoe to touch first...
…. Or am I not understanding your point?
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Mike...My understanding is that if the cam is symmetrical and the shoes "identical" they will touch the drum at the same time. There is a theoretical possibility that the lining on the end of the trailing shoe, adjacent to the cam, is nearer to the drum than the start of the lining on the leading shoe which is some distance away from the cam. Hence the suggestion, posted earlier, of relieving some of this area of trailing shoe lining to allow the leading shoe to contact the drum first.
As I see it it does not matter which way the cam rotates.....when you buy one it looks symmetrical and has no indication of a particular way to be fitted.
Of course, this is in the light of my experience and I may be wrong. So let's wait and see what the rest of the gang thinks.
Swarfy.
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Swarfy butted in while I was doin' 'Audi-Audi'.....so....
My take on the reverse lever action of that the cam is that the inside of the cam-lobe will (relatively speaking) push the shoe further than the outside lobe, so will have a better mechanical advantage.... I heard about it being done on rigid frame rigs, so tried it on my Plunger, but it failed miserably due I guess to the geometry of the uplift of the axle on the plunger unit...
...passed an audi once too!...
I went to a local cafe/bar a few years ago where there was music and shit...mate Lawrie was outside and in his usual drawl says 'howdy'....and in response I said 'owdy-owdy' and then realised there were two Audis parked behind each other where the table was....'Audi-Audi'.... hate to say it, but yea had to be there... *conf* *beer*
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Hi Mike I wish you luck and hope you’ll sort out your brakes to your satisfaction, I wasn't advising on how to ride a BSA. It's how I think about riding my own BSA and maybe why I don't find its brakes dangerously lacking. I don't ride slow because I'm riding a 59 year old A10 (in my opinion that's equally as dangererous as riding it too fast), but I do take it into consideration, look after it and try to ride it safely.
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My take on the reverse lever action of that the cam is that the inside of the cam-lobe will (relatively speaking) push the shoe further than the outside lobe, so will have a better mechanical advantage.
Yes, that is why some of us reverse the direction of cam rotation: to make the leading shoe move more than the trailing shoe.
It can work, but there may be things that can stop it working.
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Mechanical brake efficency is an art that got lost hen hydraulic brakes became widely used.
The idea that you can stop your bike with nothing more than your grip strength converting a massive amount of energy into heat is quite silly.
People just can not seem to understand physics any more.
The leading shoe should get grabbed by the rotating drum and get forced back into the pivot bolt which if it does not break forces the shoe into harder contact with the drum.
This is called the self servo action and dose about 90% of the braking effort.
All your hand is doing is preventing the shoe backing off.
Your grip strength can not lift your own weight , no matter how much mechanical advantage it uses, you are just not strong enough.
Because all of the literature around comes from the days of hydraulic braking or even worse power assisted hydraulic braking , you need to unlearn all of the rot you have read on the web and ignore all of the tosh you have seen on U-Tube.
To get your head around the physics of full mechanical brakes , you need to go back to books & magazines of the 20's, 30's & 40's.
The most common cause of poor braking is the pivot end being too far away from the drum.
This is no surprise as most BSA drums would be at or well over their wear limits.
Next is incorrect radiusing of the shoes.
To work as intended the shoe must have a LARGER radius than the drum so the initial contact will be at the end only.
The leading end digs into the drum which locks onto the shoe and forces it back against the pivot end which can not move so the shoe flexes into the drum.
Thus the rotational energy in the drum is supplying the breaking energy , not your grip.
Forget all the rubbish about different force at either end of the cam.
That is presented by clots who failed physics and were never taught any mechanical engineering.
The brake cam pivots in the center so the force transmitted at either end is EXACTLY THE SAME .
The difference is the distance each shoe moves and the speed each shoe moves.
Take your backing plate off and watch carefully what happens when you move the brake arm.
If you really need to do it, measure each one.
Mark the position of the drum on the backing plate then look & learn what is happening.
Remember that the linnings do not compress so once the first lining is touching the drum, no further movement can happen unless the cam flexes, which it does not.
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Reinforcing Trevor's info above. I posted this earlier, easy to understand - here it is again.
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Whatever radius you choose when arcing the shoes is a temporary situation.
The shoes wear to the radius of the drum fairly quickly. Eventually they wear out completely, would that initial shaping that we do still be there at that point, or will the worn out linings be at the radius of the drum they've been wearing against for years?
I'm pretty sure that initial shaping is gone quite quickly.
That doesn't mean that arcing the shoes isn't important. It gives you reasonably good contact area right off.
I've done it both ways, farted around with fitting shoes to get good brakes right off or, on another identical bike, put up with mediocre braking from new shoes that eventually bedded into provide terrific braking.
Glen
80 mph to zero on drum brakes
https://youtu.be/amMPrwtuz2U
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The brake cam pivots in the center so the force transmitted at either end is EXACTLY THE SAME .
The difference is the distance each shoe moves and the speed each shoe moves.
You make perfect sense BSA_54A10 but isn't the theory about changing the arm pull something along these lines?
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"The brake cam pivots in the center so the force transmitted at either end is EXACTLY THE SAME ."
Not quite in my view. The cam pushes on the outer edge of one shoe and the inner of the other. Surely the shoe that gets pushed on its outer edge will be forced against the drum slightly harder (and later) than the other.
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"The brake cam pivots in the center so the force transmitted at either end is EXACTLY THE SAME ."
Not quite in my view. The cam pushes on the outer edge of one shoe and the inner of the other. Surely the shoe that gets pushed on its outer edge will be forced against the drum slightly harder (and later) than the other.
Yes, the cam lobe applying force to a place on the shoe nearer to the shoe’s fulcrum is imparting more movement to that shoe.
The potential greater leverage and force applied by the other lobe, further from the shoe’s fulcrum, doesn’t get much chance to be helpful because the trailing shoe is already hard against the drum, stopping the cam from turning.
That’s why the stalwarts of the VMCC remove lining from the trailing end of the trailing shoe: taking off up to 2/3 of the lining.
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Thanks GB, a simple diagram is worth a thousand words.
Reckon you are right, RD. It's Force X Distance, a slightly different distance for the same force to act, depending which point of cam/shoe contact (closer or further from the pivot) we consider.
I missed this subtle difference earlier, so stand well and truly shown to be a fool.
But it got me thinking. On a typical plunger rear wheel, rotating anti clockwise in normal travel, the brake cam moves clockwise to brake. So the leading shoe, on the top, has the cam contact point nearer the pivot, and hits the drum first. Result good stopping power.
The front brake has the wheel rotation and cam moving clockwise, so the trailing shoe is nearer the pivot, reaches the drum first. Braking not so good. So hats off to mikeb, our intrepid experimenter and a now famous little bit of modification, to produce a reversed lever. That's the theory taken care of.
The more you think about it, is the brake much better when wheel and cam rotation are opposed? Does this explain why some later S/A cable braked models have the rear brake hub lever up or down? On this line of thinking, lever pointing down, rotations opposed, should give the best stopping power.
Swarfy.
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The post 1960 A10 cable operated rear brake with brake plate lever pointing down is a case where the cam contact edge is closer to the pivot and operates the same as the reversed levers discussed. Most of us will acknowledge that it is still a pretty mediocre brake despite the "reverse" lever. So the reverse lever is not a panacea.
If the lining is not compatible with the rest of the brake and the intended use of the bike then whatever you do to the levers will not rectify the problem. I suspect that if you were to enquire of the supplier of the complete lined shoe he would not be able to tell you the properties of the lining, how quickly it wears or how its coefficient of friction varies with temperature.(the old and famous Ferodo asbestos based moulded AM4 green racing lining needed to be hot to work properly and was reputed to squeal and wear quickly)
In times when the likes of Ferodo supplied a number of different materials suitable for bikes, sometimes to get the best results the old competition department would specify different material for leading and trailing shoe, or even two materials on one shoe. Ferodo listed 2 different lining materials for the common 8 inch full width A10 brake.
Choice, or availabilty of an appropriate lining is essential for good braking. The problem being identifying suitable modern non asbestos linings to replace the old asbestos and give comparable braking.
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Ive had very good results with the new Ferodo Linings supplied by Vintage Brake.
The new brakes seem to work just as well as the older Ferodo did when in good condition.
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The post 1960 A10 cable operated rear brake with brake plate lever pointing down is a case where the cam contact edge is closer to the pivot and operates the same as the reversed levers discussed. Most of us will acknowledge that it is still a pretty mediocre brake despite the "reverse" lever. So the reverse lever is not a panacea.
If the lining is not compatible with the rest of the brake and the intended use of the bike then whatever you do to the levers will not rectify the problem.
I agree with the above. My 1960 GF has the rear brake lever pointing down so front and rear cams operate on opposite lobes - but I suspect over such a short distance from each end of a cam to the other (not being an expert in either physics or mechanical engineering) that the difference in force applied by pulling on the lever is probably minimal. I'd sooner put my faith in good linings, brake drums and the self servo action.
All very interesting nevertheless.
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Glen - thats a good resource at vintage brakes. i might check them out. and re youtube 80mph stop on drum brakes - impressive, i had heard that vincent riders had a thing for sick teddy bears (tho not you RR!). pretty sure it was the back wheel locked and not the front.
Trevor - that's a good explanation, thanks
Dutch - is that some upmarket aussie thing these days: 'audi audi audi, oi oi oi!'
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Mike, that's correct, the back wheel locked but note the front tire distortion with 30 psi in tire.
I try to avoid locking the front wheel as it's tough to stay upright when that happens.
This stop is with the front wheel just on the verge of locking.
Squeezing a bit harder on the front will lock it.
As it is this bike stops almost as quickly as my modern bikes.
The BSA with 2ls isnt far off either.
Glen
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Glen - oops - i hadn't noticed your name on the video - sorry about the bad taste teddy bear jokes *red*
it is a good amount of squish on the front tyre
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No problem, as you can tell from the vid, I'm the king of bad taste!
Glen
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.......Dutch - is that some upmarket aussie thing these days: 'audi audi audi, oi oi oi!'......
Doesn't need much to upmarket that crap- one of the most moronic brain-deadening advertising campaigns I've ever seen....
Glen- that Teddy almost remind me of the Brer Rabbit and the Tar Baby talking book that was on my local library when my young fella was little ( his mother worked there and brought home a stack every night)...we played the bit over and over when B.Bear and B.Fox were debating what to do, and B.Bear suggested- in slow southern drawl 'let's just smack him in the head'.... has to be audibly heard to appreciate.... (there's another bit of 'audi-audi' happening ) *eek*
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BSA Brakes work and very well set up right, when Alan cambell ran classic Brakes he was truly the Master he could make any brake work, he understood the mechanics physics and what linings did what, every brake he done was fantastic i still have a few left that he done unfortionatley like all masters of old trades he retired.
My point is you do not need to convert to tls, you need a expert who understands brakes to set them up, unfortionatly now most just relign and give them back no really knowing much else. Alans alwas asked what bike is it and how do you ride and then used his experience to reline and set up correctly,
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Paul - i take your point. i went to a classic race meet in the weekend and asked half a dozen people about their 8" SLS set-up who had the brake arm rotation not reversed. most said they got someone else to do it for them. one or two described arcing the new shoes and how to do this. So i'm now figuring out how to, starting with the old fixed shoes as an experiment. also i've swapped the cam as it was binding a bit on one side.
as an aside, at the track about 50% of the 8" SLS front brakes (bsas, nortons..) had the brake arm rotation reversed, the other half not. I also talked to a knowledgeable guy in our local bsa club who said bsa published an article saying they didn't rotate the arm on road bikes due to increased leading shoe wear, only doing so for race bikes. I've yet to see the article and wonder if they always told the truth. but either way, i have more hope of getting a result.... eventually!
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here's a bit of an update for any other brake sufferers.
i put the arm rotation back to 'normal' tho kept the homemade longer arm. and replaced the cam for one that held the shoes better.
i put the older fixed shoes back in (i don't know their history but still lots of meat), chalked them up and found little other than the bits of the trailing shoe were making good contact.
so i made an adjustable rod between the arm and the cable lug, set the shoes open the correct amount (smidgen under 8") and arced the linings in the lathe using a back axle and other bits to mount it. most came off the trailing shoe around its middle. I sanded a bit more off the cam side of the trailing shoe (which makes first contact).
and... its a lot better. not great, but it actually feels like a brake that I can rely on. still abs but i might even need to check the fork oil.
so. lessons for me - start with the basics before getting creative.
there's a low spot in the drum so i might work on that some day and maybe redo the chalk for a retest. but i've had enough brakes for a while.
and here's question - how to hold floating shoes in place so i can arc them on a lathe... any ideas?
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not directly related to Mike's post..a few years ago I bought a Landrover 109 that refused to stop on the front brakes (drum brakes) . I replaced the shoes, the pipes and still it wouldn't stop. Eventually, I spent a long time trying to work out how the brakes actually worked. The lightbulb came on when I realised the front hubs had been fitted on the wrong wheels, so what should have been a leading shoe was a trailing shoe...really obvious and easy once I realised, but I wouldn't have gotten there without getting in there and physically doing the stuff. There's plenty advice and theory about on how to fix stuff that lacks the practical.
What I appreciate about this forum is there's a lot of practical knowledge shared often by people who may have had to find out at some point the hard way and now have first hand knowledge of how to fix stuff...
My 8'' front brake should be working a lot better in the near future, having read this thread...
thank you chaps..
Guy
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here's a bit of an update for any other brake sufferers.
i put the arm rotation back to 'normal' tho kept the homemade longer arm. and replaced the cam for one that held the shoes better.
i put the older fixed shoes back in (i don't know their history but still lots of meat), chalked them up and found little other than the bits of the trailing shoe were making good contact.
so i made an adjustable rod between the arm and the cable lug, set the shoes open the correct amount (smidgen under 8") and arced the linings in the lathe using a back axle and other bits to mount it. most came off the trailing shoe around its middle. I sanded a bit more off the cam side of the trailing shoe (which makes first contact).
and... its a lot better. not great, but it actually feels like a brake that I can rely on. still abs but i might even need to check the fork oil.
so. lessons for me - start with the basics before getting creative.
there's a low spot in the drum so i might work on that some day and maybe redo the chalk for a retest. but i've had enough brakes for a while.
and here's question - how to hold floating shoes in place so i can arc them on a lathe... any ideas?
make a dummy backing plate.
The important thing is how far is the pivoting ends of your shoes off the drum ?
Shimming the shoes or making up a bigger pivot will make a massive difference.
Every one worries about how close the front of the shoe is and forgets about the back.
If it is measured in 10ths of inches it is too big.
Fitting longer levers is a waste of time.
You can not stop your bike using nothing more than your own grip strength applied over 4" to 6" of travel between you brake lever & handle bars.
You need a rapid pull to jamb the leading edge into the shoe to force the shoe into the drum using the kinetic energy of the drum, not the energy in your fingers.
Hydraulic brakes work differently because you can have up to 4000 psi at the slave cyinder.
Your hand would need a lever with 9' ( yes foot ) of travel to apply the same force.
To get the brakes to work you need the shoe really close to the drum AT BOTH ENDS.
Concentrate your efforts there & you will be rewarded with an excellent brake.
Frig around with longer levers and all you will do is pull off nipples and wear out pivot holes.
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I don't use the lathe for doing the shoes these days.
I find it quicker to use the Emery and I get a better result.
Glen
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With the nz National Rally due next week I thought I’d fit a new tyre before setting off, then thought I’d might as well try to improve the crap rear brake while the wheels off. Although this is for a b31 I think it’s still relevant to A series. I used the sand glued to drum technique, and also 1mm spacer under the trailing shoe cam to ensure the leading shoe contacts the drum first. The tape i used is double sided car “moulding” tape which leaves a clear residue of sticky glue when the white backing is peeled off.
Bugger it, only a slight improvement! But it worked so so well on the front brake, WTF.
So I’m a bit like MikeB.....what to try next? Different lining material? Reduce lining length?
Anyway here’s some pics of the method. I got nearly 90% lining contact after sanding. It took 4 goes of sanding, cleaning the sandpaper and then re sanding, probably turning the circa wheel 20 times between the 4x cleaning the sandpaper using a brush. The pretty rubbish quality shoes started being too small a diameter, but after sanding became ok.
The drum was skimmed after the new sprocket welded 2000miles ago, so should be round.
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More pics of finished contact surface...note the lining material has flecks of metal in it, so maybe “sintered”?
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as you pushed the trailing shoe out with that spacer pre-sanding, did you then remove the spacer (to allow the leading shoe to make first contact)?
with the floating shoes (some pages back) i tried using norton stick-on sanding discs (150mm dia, from bunnings) cut to strips, figuring they'd be thin. it didn't work so well. but with the lathe (on the fixed shoes) I was more accurate to a smidgen under 8", which i think is correct. it worked better, but then the whole setup was different, and i note you report good contact. and this is counter to what Glen finds to work.
BTW Trevor - how do you shim the pivot end of a fixed shoe, as the shoe fits snug to the round pivot?
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as you pushed the trailing shoe out with that spacer pre-sanding, did you then remove the spacer (to allow the leading shoe to make first contact)?
with the floating shoes (some pages back) i tried using norton stick-on sanding discs (150mm dia, from bunnings) cut to strips, figuring they'd be thin. it didn't work so well. but with the lathe (on the fixed shoes) I was more accurate to a smidgen under 8", which i think is correct. it worked better, but then the whole setup was different, and i note you report good contact. and this is counter to what Glen finds to work.
BTW Trevor - how do you shim the pivot end of a fixed shoe, as the shoe fits snug to the round pivot?
Yep I took the trailing shoe spacer out before fitting the brake after sanding, I almost forgot *pull hair out* .....but not quite.
I’m hoping that maybe the shoes are very stiff and not able to take up the small difference in diameter of shoes and drum caused by the sand paper thickness, in which case I may see an improvement after a little use.
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well, we can commiserate next saturday in rangiriri. im just down for the day ride and dinner, hopefully on the a10
looking forward to it... *smile*
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BTW Trevor - how do you shim the pivot end of a fixed shoe, as the shoe fits snug to the round pivot?
You remove enough shoe from the top & bottom but leave the middle alone so that the shim is snug.
A shoe only contacts the pivot about 120 deg it is not a full 1/2 circle.
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Decided to have another go at my 58 A10 full width rear cross over (near useless) brake. Ground off about 35mm of the top of the leading shoe (cam end) lining and filed the cam on the trailing side of the cam so as the leading shoe came on a bit first.
The result was a 50% increase in braking efficiency, but still not as good as it should be, but much better than it was. *problem* *good3*
Peter
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My Brother in Law decided to take up motorcycling in his 60s and to celebrate him passing his test I offered him a ride on a "Proper Bike". At the end of his ride on my 1952 AJS 500 he said "You went to great lengths to explain the unbelievably complicated starting procedure, the advance retard lever,valve lifter, upside down gear change on the wrong side etc but you never once mentioned that it didn't have any brakes". *help* My beloved AJ has excellent brakes for an old bike but B in L rabbited on about how he could stop his oriental plastic rocket on a sixpence with 2 fingers. I had thought of offering him a ride on the Sunbeam which has a stopping distance similar to that of a super tanker but I fear he has a lot to learn before that happens.
First thing he has to learn is 'never criticise a man's AJS. *razz*.
Great thread BTW, just shows you're never too old to learn.
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My problem isn't so much the gap in braking between old and new, it's what happens to the suspension with good old brakes on a BSA front fork vs new Thruxton RBrembo monoblocks with upside down Showa big piston forks. The Big piston fork has an anti dive mechanism so even with extremely rapid negative g forces happening the front end doesn't dive. This is a big improvement over my 05 Daytona, which has equally strong braking but will dive to about the halfway point, leaving a bit of suspension.
A good hard pull on the A10 with dialed in A65double leader gives decent braking but the forks immediately go " Clonk" to the bottom, so suspension on front is nonexistant when braking hard.
Just another reason to take it easy on the old thing.
Glen
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G'day Fellas.
Brakes only slow you down. Dodging things become the norm when riding our bikes. Shame I didn't dodge the rear bumper quick enough a few years back. Broke 5 ribs and punctured a lung! i had been riding the rHonda all week but was on the A7 plunger for a club ride. She don't stop like 3 discs. *problem*
Cheers
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the reason this thread started was my heightened despair about my a10's brake after riding the modern more - the M50 brembos and Showa USD's are very addictive and encourage a riding style that is a bit lethal on a BSA.
still, the a10 brakes have been made better than they were with still other improvements possible
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yes musky I am used to dodging things, went out with my mate a few years ago and had girlfriend on the back of me. he took us down a very steep hill possibly 1n 3 or 1in4 and I ended up praying while putting full force on both brakes, ended up having to go down the inside of cars straight onto a main road hugging the curb, that was a close one. brake linings changed shortly after and now not as much praying *whistle*
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And the same girlfriend?
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yes orabanda 14 years now I think *loveit* thing is she has no fear on the back of the bike, very good passenger and we've nearly been wiped out many times by those other road users sat in their tin cans, we had one that looked straight at me then pulled out forcing me to the other side of the road --- *eek* very lucky that day .
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A good hard pull on the A10 with dialed in A65double leader gives decent braking but the forks immediately go " Clonk" to the bottom, so suspension on front is nonexistant when braking hard.
Just another reason to take it easy on the old thing.
Glen
All of which can be fixed, gold valves, new springs done to your weight even cartridge conversions, you only need to put up with how it is if you want to
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It's hard to decide how much BSA to leave in the bike.
For the time being I'm going to be happy with engine and clutch that are now working properly as well as brakes that offer some safety. The " clonk" came with the stronger braking of the 2ls.
I'll live with the stock suspension for awhile. It's not bad other than when the front brake gets fully applied.
There is a spare Showa big piston fork under my workbench tho....
Glen
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ok chaps I know my front brake is good but I am trying the emery method on the rear and now can't get the shoes in the drum without taking the brake operating pivot out , I have two strips of emery the same size as each shoe , has anyone else had this problem, at the moment I will put the lot in the swing arm and use a spacer and screw driver to open up the shoes and then turn the back wheel. I don't think I can make it any worse than it is because looking at the shoes it is way more miss than hit at present.
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A while ago I did my rear drum that way because slightly out of round. The shoes with the stuck on emery where a tight fit but went in with a bit of persuasion without having to take the pivot out.
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Think the drum needs a skim on a lathe, my local shop charges £20. Probably gone oval.
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brake drum had to be sorted when I bought it new, couldn't get a ball race in it so it was set up and skimmed to get the bearing in then the drum skimmed. think I,ve found what could have been the problem in the topic on rear single sided brake drum
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just to clear up some confusion , I put the emery in the drum to get the high bits off the shoes because looking at the shoes they had very little contact with the drum. now they are nicely uniform, some nice weather will be the time to find out.
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Having read the posts here I feel a bit more knowledgeable about setting up the shoes I have had relined. I understand the role of a fulcrum pin on semi-circle recessed shoes. With floating shoes however, when they are pushed into the drum, does the fulcrum end get drawn outwards along its flat face and create this self-servo effect? What prevents the shoes from sliding down the cam and pin under gravity and rubbing on the drum with nothing to positively locate them? Can anyone recommend any reading material on the subject.
Cheers.
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There is only very limited movement on the floating shoes. Movement limited by the drum.
See the photo you can see the pivot marks on the pads which will give some idea about how much or little they slide.
(left is a Triumph and right is BSA)
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Next is incorrect radiusing of the shoes.
To work as intended the shoe must have a LARGER radius than the drum so the initial contact will be at the end only. ***
The leading end digs into the drum which locks onto the shoe and forces it back against the pivot end which can not move so the shoe flexes into the drum.
Thus the rotational energy in the drum is supplying the breaking energy , not your grip.
Do you mean like this?
A trailing shoe marked 68-5525 which is 197mm across and only touches at the extreme edges as seen in the second image, the gap is about 1.5mm. Next to it is a leading shoe which is 191mm across and has good overall contact as shown by the blue ink. Obviously not a matched pair so which size is the best fit?
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A conundrum! Whether to substitute a full contact "191mm" shoe for a larger "197mm" trailer? The leading shoe does most of the braking, and the bigger shoe as leader is well worth a swap. Once the trailing shoe makes contact, no appreciable further cam movement takes place. Up to that point continual pressure on the cam and consequent servo action is forcing the leading shoe against the drum.
If they are identical and can be swapped, well worth giving them a go, remembering brake performance may not be up to spec to start with. Don't forget to adjust the pivot pin position if your backplate has a slotted pivot mount.
Swarfy.
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Dont swap leading shoe for trailing shoe if linings are asymetric.
The result is a considerable reduction in brake power.
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Phil - I believe the late A10 floating shoes are 'handed' being 68-5524 leading and 68-5525 trailing.
see here: http://bsa-info.nz/service-sheets/?f=1zv5Ztk8sucQpvKPoci9lBU1-iwFoZ1mL (http://bsa-info.nz/service-sheets/?f=1zv5Ztk8sucQpvKPoci9lBU1-iwFoZ1mL)
I don't think they are supposed to swap (as Julian says). I have some in the shed but haven't examined them as to why - no doubt Julian can expand on that point.
are you saying your two shoes are different sizes (radius)? they look so in the picture. do the part numbers match as above? are they a set?
it looks to me in that close-up pic that the lining is not arced tho that drum. any difference in round should be negligible, way less than 1.5mm
i think i'd be making sure I had a set of matching shoes then getting them relined and arced. start fresh.
cheers
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Phil. Following my earlier comment, I am concerned that in this case there is something very wrong with those shoes. A closer look indicates the basic castings don't match lengthwise. I hope these are not the ones which were relined. In this case swapping them around is a bad idea.
As mikeb says, start with the correct parts. If it's any help we've all been down a blind alley like this at some time.
Swarfy.
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Unfortunately, when we reach the end of the blind alley, our brakes aren't going to work!
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The 8 inch front floating shoes (Parts 68 5524 leading and 68 5525 trailing ) are handed in 3 ways;
1. The cam and pivot ends are different sizes, the pivot pad too small to fit over the cam end.
2. Asymetric position of lining on the shoe.
3, The width of lining is not symetric to the cam, it is displaced towards the brake plate side.
So they only fit one way.
Non floating 8 inch front shoes as point 3 above.
Above for genuine BSA shoes, I cannot make any comment about pattern shoes or Triumph shoes (part numbers starting W)
The 7 inch rear full width with floating shoes points 1 and 2 above so only fit one way.
7 inch non floating shoes same part both shoes and interchange with each other.
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Yes Swarfy, a conundrum, and potentially a dangerous one. I wouldn't have liked to fit them and then discover I couldn't stop. Mike they are of different radius and were bought as part of a job lot of brake shoes. Julian I think they might be aftermarket items (they are marked MC ltd) as the ends are identical in size so in theory they could be swapped over, keeping the assymetry, but I wont be trying that, I can hear the metal of the wider shoe rubbing against the drum, not good. I will keep my eye out for a 191mm trailing shoe and will try those at some time. The lining offset explains why the shoes are just 1mm from the outside edge of the contact area with about 4mm of unused inner drum face. The shoes I had relined by Villiers are of the fixed pivot type swarfy and he did a good job of sizing them with thicker cloth woven sintered material.
As I was arcing them in I noticed two things. First, when I operated the brake arm in the opposite direction mimicking the reverse fit of the arm, as in a previous post here, the brake worked better and was sharper so I would say it works! Second, when I centered the shoes, the brake didn't work well. BUT, when I operated the arm in the reverse way (anticlockwise) and then tightened the fulcrum they became quite good. I can't determine how good until the lockdown ends but will keep you informed. Thanks for your input guys.
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Next is incorrect radiusing of the shoes.
To work as intended the shoe must have a LARGER radius than the drum so the initial contact will be at the end only. ***
The leading end digs into the drum which locks onto the shoe and forces it back against the pivot end which can not move so the shoe flexes into the drum.
Thus the rotational energy in the drum is supplying the breaking energy , not your grip.
Do you mean like this?
A trailing shoe marked 68-5525 which is 197mm across and only touches at the extreme edges as seen in the second image, the gap is about 1.5mm. Next to it is a leading shoe which is 191mm across and has good overall contact as shown by the blue ink. Obviously not a matched pair so which size is the best fit?
Yes rather like that
The idea of the steel caps on the brake shoes is so you can shim the pivot end of the shoe to account for wear in the drum.
just the same as the oval pivots on the Ariel type hub
The pivot end of the shoe should be as close to the drum as you can get it.
The closer the better
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Thanks Trevor, getting hold of those end caps is a bugger tho. Might have to make something myself.
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Decided to have another go at my 58 A10 full width rear cross over (near useless) brake. Ground off about 35mm of the top of the leading shoe (cam end) lining and filed the cam on the trailing side of the cam so as the leading shoe came on a bit first.
The result was a 50% increase in braking efficiency, but still not as good as it should be, but much better than it was. *problem* *good3*
Peter
This worked for a while but gradually went back to being next to useless, so start again, having brake drum skimmed and seeing if I can get some different linings. would like to get some with some nice asbestos in them *whistle*
Peter
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Tacking today's conundrum onto an old but very informative thread.
The PO had the drum skimmed and the shoes relined or bought new shoes maybe , I'm not sure but either way it is all like new in there.
That said, I've never been happy with my front brake (who is?) Previously I found the PO had got the linings in the wrong way around (for leading and trailing shoes) and the steel shims at the wrong end (cam end of the shoes) so I happily reassembled by swapping the shoes around and lo it was somewhat better but still not great.
At this point I will say I made an error because I failed to realise what I've found now which is that the shoes are offset to the cam and pivot centreline and therefore can only go in one way around. This meant that I'd been happily tooling around with the shoes too far into the drum, and about a 6 mm gap to the upstands on the backplate although blissfully unaware all the while, it's been like this for two years!
So now with the shoes reassembled in the right way, contacting the upstands, it seems to me that the linings are actually bonded at the wrong end of the shoes? I just thought I'd run it past the brains trust here before I rush off tomorrow have these relatively unworn linings taken off and a new set bonded in what I believe is the correct orientation. I've done some measuring and there is room due to the drum width being greater than the shoes so I can fit them this way and they will still run correctly in the drum without running over the spoke heads... *eek*
I'd like to confirm I have the correct shoes?
The shoes are now correctly assembled i.e. butting up to the upstands on the brake back plate?
The linings are indeed incorrectly bonded at the wrong end of the shoes?
The shims should be put at the fixed pivot end?
Thanks in advance lads, so helpful for us with less knowledge of these old machines. *smile*
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(https://i.postimg.cc/MKGpxSvL/IMG-3259.png)
That looks like the shoes have been lined the sensible way, with an unlined section at the trailing end of the trailing shoe.
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Hi BON and All,
Those shoes look like the commonly available pattern items ?
I tried a set of them and no matter what I did could not make them work !!
I went back to the original shoes and got them relined with oversize linings (soft) and turned them to fit the drum.
Now i have a brake *smile*
John
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Thanks TT and John. I was going by the info put up earlier in this thread and in others on the forum showing the linings in relation to leading and trailing shoe position. I've attached another photo of what I've got and Roger SB's graphic for reference. With my shoes assembled what I thought was correctly i.e. against the brake back plate with no gap the linings seem to be bonded at the wrong ends of the shoes. My yellow arrow denotes wheel rotation. I can reverse the shoes but then they are sitting about 10mm off the brake plate upstands which must be there for a reason?
One of the shoes has a part number 68-5524 and is marked with 'L' I assume for leading the other I can't make out but is the opposite orientation. With this L shoe fitted as the leading one the linings are then correctly positioned per Roger's drawing but they are way off the back plate as described above. *dunno*
John your comment about material certainly rings true but our best chance here in Adelaide is 'Power Brakes' and they say the material looks the same as they would fit and is generally well liked by the old bike community here. It's a soft black material with some sintered metal in it.
My drum measures pretty much spot on 8" and the shoes are only sitting about 1mm off. I guess I could try spacing them out a little, maybe a touch more on the trailing shoe and arcing them in the lathe.
As TT has alluded trimming some material off the trailing end of the trailing shoe may help the leading shoe bite first so I might have a go at that before I do anything else.
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Hello Ian,
The leading shoe will make 80 % from the brakeforce. The geometrical design of this brakes isnt realy good. The brakecam is symetrical that will cause that the trailingshoe will come first to the drum. A good improvement is to grind down the camside that feeds the trailing shoe. Make the cam asimetical to be shure the leading shoe comes first.
regards Klaus
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(https://i.postimg.cc/bY5nqbGk/IMG-3261.jpg)
OK, so according to that, they were concerned about too much self-servo action locking the wheel up and throwing you off the bike, to your doom.
A timely reminder that we experiment with brakes at our peril.
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G'day Fellas.
*lol*I keep saying "brakes only slows you down". Learn how to dodge & weave *smile*
Now to dodge and weave. *whistle*
Cheers
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Think along the lines of a giant hand moving the linings along the shoe in the direction of wheel rotation until the lining reaches the end of the shoe. It's the same for all drum brakes with leading and trailing shoes and is an easy way to correctly orientate otherwise identical shoes.
Shown to good effect in the above line drawing. Removing lining surface from the trailing shoe means the leading shoe contacts first. Reverse lever arrangement and unequal cam mods are all other things to try, but as mentioned, playing with brakes carries a certain unease....
A better quality lining material suited to riding style could be what is needed, rather than one size for all processed cardboard variety. Glazed linings can be improved by removing the glaze with a belt sander, light tickle, eye protection, face mask, outside in the wind.....Greasy or otherwise contaminated shoes could be revived by boiling in HARPIC toilet cleaner, reckon that to be a myth, but it did appear in print back in the day.
Maximum leverage is applied as the operating arm is at 90 degrees to the cable, you want the arm to approach 90 in normal use, over 90 is less leverage and the sign of a well worn brake. Some brakes have a floating or adjustable pivot position. Getting this adjusted correctly will centre the shoes, sadly not a facility available in this case. Floating shoe design, see post at the beginning of this topic, goes some way to achieving this with a fixed pivot.
Swarfy.
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(https://i.postimg.cc/bY5nqbGk/IMG-3261.jpg)
OK, so according to that, they were concerned about too much self-servo action locking the wheel up and throwing you off the bike, to your doom
I guess no-one told this Velo owner-
https://www.ebay.co.uk/itm/186991206194
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I reassembled everything with the correct orientation (as it was when it came apart) and will live with the gap between the shoes and the back plate up stand features. The more I thought about it the more I think this is how it should be. I think they are just an insurance back stop to prevent displacing the shoes when refitting into the drum and when fitting the springs. While it was apart I took the opportunity to file away about 25% of the trailing end of the trailing shoe which should encourage the leading shoe to bite first. I'm not keen on grinding the cam down Klaus, well not yet!
I'll see how this goes. There are signs the leading shoe is starting to bed in, it probably needs another 1000km or so. Trouble is I don't use it enough...
John, I like your idea of fitting oversize linings but with these floating shoes I can't see a way to hold them on the back plate adequately to machine them on the lathe without making a very elaborate jig! Are yours the same? How did you hold them?
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Hi BON,
I went back to the standard shoes for the oversize linings.
Just wondering if one could make a hollow mould with blue tak or similar and epoxy the floating shoes to the pivot *????* then some heat will soften the epoxy to clean them up after machining *????* .
I use soft wire to hold the shoes together on the backplate
John
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I came upon this thread when looking for information on adapting some 8” Triumph/BSA sliding brake shoes to fit my 1933 M.G. which, believe it or not, uses essentially the same design of brakes. As you can see, the installation has been successful although I’ve put very few miles on them so far so the jury is still out on how effective they are.
However, the amount of misinformation that has been posted on this thread has prompted me to post some of the FACTS that I have uncovered during the research I did before embarking on my brake adaptations. These are not my personal opinions and they can be confirmed by reading any brake theory textbook that covers fixed cam operated drum brakes. So here goes!
1. With fixed cam brakes both shoes are equally displaced by the cam (subject to the slight variation caused by where the cam makes contact with each shoe) and so must wear equally, and thus must do equal work. This is sometimes referred to as the equal work condition. The oft quoted claim that the leading shoe does 60-70% of the work is, quite simply, wrong. Once bedded in, both shoes do equal work.
2. The self-servo effect that is present on the leading shoe is not caused by the lining 'wedging' against the drum - it is caused by the moment about the pivot end of the shoe of the friction force of the lining against the drum which tries to increase the force with which the lining contacts the drum.
3. The length of a lining is generally in the range of an included angle of 90° to 110° with the Triumph (and I assume the BSA) shoes being 110° (the same as my M.G.). The length of the lining is not a factor in the amount of self servo generated.
4. On pivoted shoes the lining is equally displaced about the centre of the shoe as this is, more or less, where the centre of pressure lies. In the “off” position, with the cam flat, new linings should be concentric with the drum and with a radius slightly less than the drum. (On my M.G., 'slightly less' means 1/64” (15 thou) and I imagine the figure would be the same for Triumph/BSA shoes.) Because of this concentricity, pivoted linings make initial contact with the drum more or less in the centre of the lining and bed-in outwards from there.
5. On sliding shoes, the linings are displaced in the direction of rotation of the drum towards the trailing end of the shoe. This is because the centre of pressure on a sliding shoe is not in the middle, as it is on a pivoted shoes, but moves towards the trailing end. The higher the coefficient of the friction of the lining, the more the centre of pressure moves towards the trailing end. Hence the offset location of the linings. Because the shoes are not constrained by the pivot they are free to move slightly and thus self centre in the drum. Linings on sliding shoes, therefore, have the same radius as the drum and make contact more or less along their full length. In consequence, they need much less bedding-in than pivoted ones.
6. On the question of shortening the trailing lining, you won’t find a direct explanation of the benefits of this in the textbooks but it’s something I have discussed at some length with a university academic who teaches a course on brake theory. The logic of the modification is that by shortening the lining, for the same force applied to the shoe, there will be greater pressure on the lining (because of its smaller area) which will therefore wear more quickly and thus, because of the equal displacement of the fixed cam, the leading shoe lining will also wear more quickly and thus do more work, i.e. provide more braking power. The work done by the shortened trailing lining remains the same.
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The oft quoted claim that the leading shoe does 60-70% of the work is, quite simply, wrong. Once bedded in, both shoes do equal work..
So a twin trailing shoe brake would be as good as a twin leading shoe brake?
(https://cdn.apartmenttherapy.info/image/upload/f_jpg,q_auto:eco,c_fill,g_auto,w_1500,ar_1:1/k%2Farchive%2Fcd48babc44200d5c52c9d54b8308fa8585c1e386)
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Clearly not. But a twin trailing shoe would be pretty much the same as a leading/trailing shoe setup.
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Hello PrewarMG,
very interesting - please keep us up to date with your practical experiences.
Which books are you having at hand?
Thanks in advance.
Best regards, Manfred
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Hi Manfred,
Thank you for your interest in my little four-wheel project.
Some suggestions for further reading *smile*
Probably the definitive book in the UK on the theory and practice of brakes is Braking of Road Vehicles by Andrew Day, published in 2014. Andrew Day is the Emeritus Professor of Engineering at Bradford University where he established the Braking Research Centre which is today the leading authority in the UK on braking systems research and development. At around 450 pages, it's not for the faint-hearted but the sections on drum brakes do cover some of the vagaries of fixed cam systems as these are still used today in heavy truck brakes, albeit with S-cams and not the flat cams we're familiar with.
An earlier book of the same title by by Newcomb and Spurr published in 1967, at about one third the size is slightly easier to digest, but in consequence, is not as comprehensive.
However, I also sourced quite a number of technical papers presented to the Institution of Automobile Engineers in the 1930s and 1940s which cover the transition from pivoted shoes to sliding shoes which occurred in the 1940s. A couple of these are by F.A. Stepney Acres who was widely regraded in those days as one of the gurus of brake design and development.
Initially I also used Fundamentals of MOTOR VEHICLE Technology by V.A.W. Hillier and Advanced vehicle technology by Heinz Heisler but while these were useful for getting to grips with the basics, they lacked the analytical detail of Day's book and I rarely look at them now. There are also some useful little nuggets in A Technical History of the Motor Car also by Newcomb and Spurr, published, I think, in 1980
Regards,
Simon
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G'day Simon.
Very informative, thank you.
I googled Mr Days book. It can be downloaded through Google Books for $115AU
https://tinyurl.com/ys89dprw
Cheers
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Clearly not. But a twin trailing shoe would be pretty much the same as a leading/trailing shoe setup.
Good information Simon, very interesting and thanks for your contribution, however, I'm finding it hard to accept your assertion above, if I've understood what you were explaining correctly...
A twin trailing shoe brake would have no self servo effect as I see it whereas a conventional leading/trailing shoe set up at least benefits from the servo effect on the leading shoe does it not? Therefore how can the performance be similar? Equally I think we would all agree and expect from theory and practice that a twin leading shoe set up would be the best performer for the same reasons would it not? (all other aspects of design being equal of course.)
Confusedly Yours *problem*
BoN
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If both shoes do equal work - which they do - then the leading shoe has the same braking performance as the trailing shoe and therefore twin trailing shoes would have the same performance as a leading and trailing shoe.
The shoe factor, i.e. the braking performance, of the leading shoe in a leading/trailing setup is the same as the shoe factor for the trailing shoe - hence the equal work equilibrium. The effect of the self servo is to reduce the force on the leading shoe from the cam while still providing the same braking performance. The fixed cam provides equal displacement but not necessarily equal force. The self servo effectively 'lifts' the shoe slightly off the cam, reducing the force from the cam and the resulting reaction to the force applied to the cam by the lever is taken by the cam bush.
And yes, of course, twin leading would be much, much better as both shoes would be able to benefit fully from the self servo. It seems to me to be quite feasible to convert my brakes to twin leading as the pivot post is held in a bronze bush the same as the cam so two single lobe cams could easily be fitted. The biggest problem is how to operate them. A cable pulling the levers together would be possible, but there’d be twice the pedal travel and shortening the brake levers could be tricky. Work in progress!
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Simon Hilliers book is the one i have from the 90's at tech . i still don't fully understand steering geometry though ----thick me.
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*smile*
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The effect of the self servo is to reduce the force on the leading shoe from the cam while still providing the same braking performance. The fixed cam provides equal displacement but not necessarily equal force. The self servo effectively 'lifts' the shoe slightly off the cam, reducing the force from the cam and the resulting reaction to the force applied to the cam by the lever is taken by the cam bush.
I’d say that theoretical description is compromised by absence of absolute rigidity in various components and fixings. If the leading shoe is tending to be lifted off the cam, the cam is tending to follow it, using up the bush clearance and flexing the backplate, so maintaining force on the leading shoe.
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Indeed, I’d agree that any tolerance at all in the bush will effectively allow the cam to 'float' and thus the leading shoe will benefit from the additional self servo. But once that tolerance is used up by wear in the leading shoe lining, you’re back to equal displacement and equal work.
This is the standard theoretical analysis of fixed cam brakes. A mechanical system with cables and levers and bushes is always going to be to some degree different in practice than the theory might suggest. But the basic principle remains, and was recognised nearly a hundred years ago in theoretical papers - as one paper written in the late 1920s put it “ Servo shoe wears more rapidly until each shoe does equal work, then both wear equally.”
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once that tolerance is used up by wear in the leading shoe lining, you’re back to equal displacement and equal work.
We centre the backplate, obviously, if the braking effect appears to be diminishing.
Some fanatics even swap the shoes over.
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H Simon (MG)
As you have just joined the Forum an introduction post regarging your A7/10 and riding history would be most welcome
As to the practicalities of "twin trailing" shoe brakes *eek* All I can offer is the experiences with the Taylor Dow TLS brake on my Super Rocket and memories of some other bikes I rode back in the day.
The Brake on my SR is excellent when riding the bike, It is possible to lock the front wheel if too much hand pressure is applied, however the brake will not hold the bikes weight when wheeling the bike up the ramp loading into or out of my van (opposite rotation)
John
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John,
As I said, my reason for joining the Forum was that, having researched the topic of fixed cam, SLS brakes for my M.G and in doing so discovered the similarities between the M.G. and Triumph brakes, and having subsequently adapted Triumph motorbike brake shoes to fit the car, I was so appalled at the vast amount of misinformation in this thread that I felt some basic facts needed to be stated lest others might believe the nonsense that had been written.
Regarding my A7/A10 experience, I have never ridden a motorbike of any sort and only, three times I think, have I ever been on a powered two-wheeler. Once, as a very small boy on an uncle's motorbike, once as a student on the back of a scooter, and once a few years later on the back of one of those little Honda thingies.
As for twin trailing shoes, they did exist - Jaguar fitted them to the Mk VII model in the mid-1950s but they were complemented by massive vacuum servo assistance. Their advantage was smoothness of operation and complete stability with no tendency to grab whatsoever. But not very practical on a motor bike (or a pre-war M.G.!)
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As for twin trailing shoes, they did exist - Jaguar fitted them to the Mk VII model in the mid-1950s but they were complemented by massive vacuum servo assistance..!)
Perhaps they needed “massive vacuum” servo assistance because twin trailing shoe brakes are not really as effective as single leading shoe brakes?
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Stopping any car weighing nearly two tons with drum brakes of any sort would need a fair amount of servo assistance. The inherent stability of twin trailing shoes was presumably the attraction but the cost and complexity of the operating system probably didn’t warrant that approach as the same operating system could operate twin leading shoes with all the benefits that they would bring.
P.S. I think, but can’t be certain, that the Mk VIII Jaguar switched to twin leading shoes, or perhaps even discs?
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Welcome MG,
I have seen photos of a few TLS conversions where the lever(s) are inside the hub rather than external
I thought the usual fix for prewar MG's is a hydraulic conversion *????
The attached 4 shoe brake takes some "figuring out" *eek*
John
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Fabulous! I love the four brake shoe setup! However, it would almost certainly be a failure. I mentioned F.A. Stepney Acres (above) and in one of his papers he describes just such an experiment which, in his words, “was a complete failure; it overheated very rapidly, with consequent early fade, and it seemed as if it would never cool off”.
The internal linkage for the TLS setup is interesting but with the large hub for the wire wheel (see attached photo) I’m not sure there’s room for something like that. But certainly food for thought. Thank you.
Fitting hydraulics is of course an option but not one I’d personally consider. There are also 12” cable operated brakes on later MGs and these are often fitted. But I’m hopeful that my modified Triumph shoes, with shortened trailing linings in due course, will suffice.
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you need to cut holes in the floor and turn it into a flintstones car then get some bigger boots on , now where's my black &tan *beer*
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you need to cut holes in the floor and turn it into a flintstones car then get some bigger boots on
👍🤣
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Welcome MG,
I have seen photos of a few TLS conversions where the lever(s) are inside the hub rather than external
I thought the usual fix for prewar MG's is a hydraulic conversion *????
The attached 4 shoe brake takes some "figuring out" *eek*
John
I still have "no idea why my front brake is useless" but from what we had all agreed... are those linings at the wrong end of the shoes on the Manxman TLS brake John?
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It’s hard to tell which is the abutment end and which the cam end, but if the arrows in the picture below are pointing at the abutment end, then they would appear to be pivoted shoes and the linings should be centrally disposed on the shoes, not offset. If, however, the arrows are pointing at the cam ends, then the shoes do look to be sliding and so the linings are correct, assuming clockwise rotation of the wheel.
P.S. I don’t think pivoted TLS are very common and the ones in the picture below are BMW (R75 I think?)
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Hi All,
I'm pleading the fifth amendment *pull hair out* *pull hair out*
John
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John *lol* *help*
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The oft quoted claim that the leading shoe does 60-70% of the work is, quite simply, wrong. Once bedded in, both shoes do equal work..
So a twin trailing shoe brake would be as good as a twin leading shoe brake?
I had a faint memory of reading something about "2TS" brakes a long long time ago. A bit of rootling around brought me to page 259 of Robert Ireson's good basic guide to motor vehicles, the Penguin Car Handbook, revised edition 1967 (first published in 1960).
Where the man says (and I quote word for word):
"A more recent development (than the 2LS brake) is that of the two trailing shoe brake (2T.S.) This arrangement has been shown to be less sensitive to high temperature effects (fading) than the two leading shoe system, and also provides more consistent and progressive braking. ('Progressive' implies that braking effort is proportional to pedal pressure.) However, since the tendency is for the brake shoes to 'unwrap', higher operating pressures are required, and in order to reduce the force required at the foot pedal it is usual to provide servo assistance . . ."
Not a two-wheeler option then unless I'm missing a trick. And moot probably in a world of universal discs, except on air-braked Heavies.