Worty's front brake

[Worty]

I think if the shoes or cam were different (by design or thickness of lining), I'd never do anything like this.  However, it would seem to me that one or the other shoe is going to have a self servo effect one way or another.  In its present position, the cam would rotate anti clockwise, but would still push both shoes to the drum.  The 'lower' shoe would still acquire self servo effect.  If the cam were designed differently, I could understand the issue better, but it's not.

I'm reminded of someone who I read about changing their rear brake from underslung to up 'n' over for modification reasons, and there didn't seem to be an issue.

I know the brake stops the bike extremely well.  Reckon I'll do some testing with it and report any issues back.

[RogerSB]

Given that the leading shoe and trailing shoe are reversed when going backwards, wouldn't this simply be the case with my set up?

As the drum is going around the same way as before, theoretically, it would, but I'm as much in the dark as you are on that one Worty. Personally I wouldn't change it from the way BSA intended, as they would have thought it was the most efficient way.

As Rob was thinking in his post 3360, when the cam rotates, even with the pivot point being central,  does it push on the shoes slightly sooner at one end than the other and make a difference? 

Also, if you removed the shoes and changed them around, even if unintentionally, the less worn one could have ended up the leading shoe and doing most of the work. That may be why your brake seems a lot better.

Rog.

[RogerSB]

Worty, Yes, looking at the brake plate from the outside, if you could see through it, the cam in your mod will rotate anti-clockwise (a bit), but looking at it from the inside everything will be the other way around - just to make it more confusing. 

Rog.

[Worty]

I've just had an idea which may be total rubbish but I'll have a go anyway. 

If I rotate the cam a full 180 degrees (taking wheel and shoes off), would that put the 'square' the lever sits on in a different position to what it has been when originally mounted?  Given my theory that the cam doesn't mirror the square end exactly, this may mean that the square end is in a better position to mount the lever more conventionally???

[RogerSB]

Worty, I hate to say it but I think you’re chasing rainbows.  Presuming that your brake drum is in good serviceable condition and you have the correct brake shoes, decent linings, correct cable, adjuster and control lever the brake should be adequate for how we should ride a 60+ year old BSA, especially in todays busy and faster moving traffic.

Others may dispute that and want to ride fast and furious regardless. In the 50s and 60s the A7 and A10 were well up to the job, but today they're ancient technology in comparison.

The brakes are standard on my A10 and it has a sidecar attached, but I don’t find them so inadequate that I feel I need to alter them.

Rog.

[Joolstacho]

Am I stoopid? (no answer required thanks!), but are we overthinking this?
I've always thought that SLS = one end of each shoe stays effectively motionless, not moving out but may slide along the pivot, whilst the other ends move outwards, actuated by the cam.
whereas with TLS = BOTH ends of each shoe move out -actuated by a cam on each end.
?

[limeyrob]

Er no.
SLS a single cam moves the ends of both shoes but that means one shoe moves into the direction of rotation and the other moves away from it.  This means the rotation drags one shoe in more (self -servo) and the other shoe is pushed back.
TLS - 2 cams and 2 pivots. So one came moves one shoe and both cams are pushing the shoe into the rotation so both get self-servo.
I don't know the exact ration but the leading shoe does at least twice the braking of the trailing shoe so have both shoes leading makes a big difference.  But a TLS has to be set up right and the OIF conical hub was a way to make the brake self balancing.  Its a good design but poorly executed.

[Worty]

Rog - thanks mate, just overthinking out loud, which I have a tendency to do   I agree with your conclusion that if all is good, there's nothing to worry about.

Rob - agree with the SLS summary, don't have any experience of TLSs.  You've answered my question on the self actuating shoe bit as there is always going to be one shoe opening against rotation regardless of the position of the lever and whether the cam is operating clockwise or anticlockwise.

[limeyrob]

Where we get deep into the weeds is the exact difference between the 2 shoes and the cam on a SLS.  The cam is a flat(ish) plate and so one part is nearer the drum and once further away.  The end near the drum is further from the shoe pivot so it have more leverage, the other end is nearer the shoe pivot so it moves the shoe very slightly more.  It seems that the view is that moving more is more important than force as it means the leading shoe gets first contact.  Can't help thinking that as someone said above, just sanding a bit off the trailing shoe would do the same.  Some trailing shoes have a lot of the lining cut away.

[Worty]

Makes sense about the pivot Rob, but the shoes are identical.

I think I'll test it out to see if I'm happy with the braking force.  At present, pushing the bike and hitting the brake makes the forks dive.  For our bikes, I'd say that ain't too bad.

[Adler]

Hello Forum,
it seems, "the brake lever rotating with or rotating against the wheel"-thing is still awaking again and again. And in most of the cases there is eventually the statement, that the brake shoes are equal - and in most of the cases they are - but then one forget, that the "root cause" is the cam. The cam is a (flat) lever which moves both shoes to the same value - BUT: the outer contact point moves the one brake shoe on a bigger radius than the inner point, which moves the other brake shoe at a smaller radius. Result: the latter brake shoe contacts the drum first. See the post from BSA_54A10: https://www.a7a10.net/forum/index.php?topic=14952.msg125587#msg125587.
Best regards to the best forum ever.
Manfred

[Worty]

Cheers Adler, I'd forgotten to update on this thread.  I've done around 300m with the current set up and it works better than before.  Adjustment at the bars is spot on, and my braking issues are sorted.  Certainly understand about the radii thing, but my original question was whether changing the rotation of the cam makes any difference to anything given that the shoes are identical (at least they are on my bike).  Some have mentioned that some shoes have a chamfer, but this is not the case with mine.

All I do know is that the standard set up didn't allow me to set the brake up with enough adjustment at the bars for it to be effective.  The angle of the brake plate lever was too far out either way (moving the brake plate lever forwards or backwards).  In the new position, I have almost all the adjustment at the bars, and a fabulous brake.  Brake shoes have loads left on them, by the way.