sidecar tuning

[Brandis]

The sidecar is not original.  I have a wobble in the front forks above 20mph.  I know it's a combination of bike tilt and sidecar toe-in.    Does anyone have some tips?

And, no, I shouldn't be bothering you because it's on my M20, but the M20 chatroom seems to be shut down.   I need to get ready for the Distinguished  Gentlemen's Ride.

[berger]

take your tie off and use it as a damper on the forks, only joking i have no idea

[Brandis]

Does it have to be a BS Whitworth tie?   

[Greybeard]

This may be useful:
https://www.dmcsidecars.com/blog-3-1/basic-sidecar-installation-tips#:~:text=A%20sidecar%20applies%20a%20lot,the%20suspension%20for%20ride%20height.

[Kickaha]

The sidecar is not original.  I have a wobble in the front forks above 20mph.  I know it's a combination of bike tilt and sidecar toe-in.    Does anyone have some tips?

What toe in and bike tilt are you currently running ?

[Brandis]

It sounds pretty amateurish but . . . .

I heard somewhere, probably in a noisy bar, that, because the sidecar drag tends to steer it in that direction, so you counteract that with a slight bike lean away from the sidecar.   I also recall hearing that the sidecar wheel line should meet the axis of the bike about 18' ahead.   That doesn't work.  Adjusting the toe in seems to increase or decrease the frequency of the front wheel wobble but it doesn't cure it.  A passenger in the sidecar helps.

I just replaced the fixed length angled struts with adjustable ones to play with that but haven't done a road test. 

I assumed someone out there would have a more scientific approach.

[RogerSB]

The .pdf guide I have attached was compiled from various sources to help when I fitted a sidecar to my A10.  It may give you some idea of what you need to do. The last page is the measurements I ended up with through trial and error over several months of testing. Luckily an  A10 has a steering damper, which when adjusted down is a big help dampening out any handlebar shakes.

Good luck with it,
Rog.

(Edit: new .pdf attached, as first one didn't have the last page with my own measurements in it.)

[sean]

good video on u tube with one of the new BMW 1800s and an electric adjustable camber control [BMW r18 first edition with Hannigan heritage sidecar]
looks great .....

[Brandis]

I'm getting a lot of info that suggests my initial set-up was pretty close.  2 degree lean out.  Good toe in.  But no one talks about tuning out the wobble. 
There was the suggestion that the damper was key to it all.   M20s had no damper but sidecars were very common.   The frame and forks are set up for them.  Maybe dampers were fitted on models with sidecars ?  Maybe I should   rummage through the junk room and find one that I fit. 

[Kickaha]

  But no one talks about tuning out the wobble.

Tuning out the wobble possibly involves changing the trail

There was the suggestion that the damper was key to it all. 

I think dampers disguise problems, I don't think they fix them

[Black Sheep]

Our Gold Flash never had any wobble problems. It was only when I took the sidecar off that I found that the fork stanchions were bent back. Not that I would recommend riding your outfit into a solid wall...

[RogerSB]

Yes trail can have some effect, it's called caster on a car.

Most bikes are stuck with what we have though. Black Sheep was lucky to have it already done for him 

Illustration of Trail attached, for those not be familiar with it (click it to make bigger).

Rog.

[Swarfcut]

 Considering that diagram, altering the length of the fork leg moves the centre of the hub forwards or backwards in relation to the steering axis, and by my reckoning alters the degree of "Trail". So the length of the fork springs and consequent ride height could be a contributing factor.
  Am I right? Waddya reckon?

 Swarfy.

[Brandis]

The M20 was the most likely BSA to ever get a sidecar.  I can't imagine the basic frame design is incompatible with that.  I'll fit a damper to the existing mounting points and get back to you.

[Topdad]

Hi Brandis , sure a few adjustments will help ,first are you using the damper you will need a bit more than a solo, next check the tow in of sidecar to bike  easy check get a legth of straigt wood hold or position against the sidecar wheel then same against the bikes wheels then measure the gap and  check difference betweet the front and at the back if I recall  it was about 1i/2 inches but a long time ago ! after that re fer to position of sidecar wheel in relation to between the bikes wheel it shouldn't be it shouldn't be inline but further forward  can't think of more I'm sure one of yours inst set up properly .And to finish I read an article in i think classcic bike  where a guy picked up a new watsonian and enfield combo stated to go down hill after it started with the comment "apart from the shudder a starting off which is inevitable " its bloody not I screamed  ,no damper on enfilds and a small bike  I didn't have a shudder on my first a10 at all  so good luck and have some fun its a great !