fork leg spacers

[little kwaka]

hi guys, would like a second opinion,,, im building a reliant trike i have recently bought some slab alloy yokes that are 39mm my fzr600 front end has 38mm fork stanchions i have been told i would be able to use a spacer to shim them by using pieces of tubing with a slit in, been told this will do the job and be safe,,, i need some re assuring im afraid as its the forks we are talking about here,,, what do you guys think
regards
tony

[andyrennison]

No idea, but welcome to the madhouse forum Tony

[Olds]

Not sure where you will find tube with 0.5mm (0.019") wall thickness.
Personally I would prefer flanged spacers inserted from below and bonded into place, but your wall thickness would make this difficult.

[andbolt0]

you could hav some top hat spacers made to suit the forks diameter and bore the yokes out to suit or try getting fork legs the right dia

[Manky Monkey]

Half a mill thick would mean a strip of ali or steel about the thickness of a Coke can wrapped around the fork legs then clamped by the yokes. Probably safe enough if it's slightly thicker than needed so the yoke clamps down tight onto it, but not good engineering.
As the clever ones have said, better to get the holes bored out to a bigger size if you can & some thicker shims made, preferably with a flange on them so they can't drop out of the holes, & slit so they can grip the forks tight as the yokes bolts are tightened.
In the real world of backyard builds, the Coke can shim would probably work fine, but your MOT man might not like it & it might be worth the 50 quid an engineering firm might charge you for the work, for the peace of mind of knowing it's done right.

[hunter]

Or you could get yourself a pair of 39mm fork legs,
Yamaha TZR250 1987-91 are 39mm.

[Manky Monkey]

There ya go. Problem solved! 

[stumpy]

make the slot where the clamp bot goes 1mm wider the tolerance your talking of will be taken up and an easy fix

[andbolt0]

the above reply is incorrect as every 1mm  reduction in dia  needs 3.142mm taking off this is the rule of pye  which is 
circumferance =dia x pye(3.142) at the end of the day the forks are keeping you up off the road surface

[morrag]

The mathematics are of course correct, so if you must use the stanchions and yokes as they are, use 20thou. 'shims' in each yoke, and torque the clamp bolts up, you should be fine, Morrag

[little kwaka]

thank you very much for all the suggestions and advise above,,,, i would like to keep it on three wheels and not end up with it a snowplough for tarmac,,,,, the tzr forks sound the safest bet,,, suprised realy there 39mm and a 250,,, my forks are 38mm and from a fzr600,,, hopefully bits might interchange, ie wheel callipers etc, yamaha to yamaha,,,
once again many thanks guys
much appreciated
best regards
tony

[hunter]

If you need any more dimensions for the TZR forks i have a set here that i am using.

[little kwaka]

hi hunter, actually that wouldnt be a bad idea as my trike is more than half built with the fzr600 front end in,,, whats the height / lenth of the tzr legs inc wheel,,, what size front wheel you on,,,, any idea if tzr and fzr might be interchangeable ie wheel callipers etc,,, thanks for your help
much appreciated
tony

[hunter]

Going over the workshop later,Will measure everything.

[Olds]

Any chance of some pics Tony ?  Of the trike that is.
You may have noticed, we like pics.