leading links bearings

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Sofa
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leading links bearings

Postby Sofa » Mon Oct 02, 2006 10:24 am

I recently bought a set of second hand Unit leading links for my outfit. At a recent sidecar fed rally a guy advised me to look at the pivot bearings before fitting them. I was very surprised to find that the pivot had ball races in, as even with my limited engineering training they do not seem the ideal thing for such an application. They allow some sideways movement and there is no need for a pivot to rotate all the way round, thats what ball races are for!
He put me on to a guy who converts the pivot to a rubber bush. He uses a swinging arm bush from a 125 Suzuki. The bush is metalastic i.e. steel outer, rubber inside and steel inner but he has to make a spacer as the outer diameter of the bush is smaller than the inner diameter of the pivot tube. he also has to machine the inner steel tube to shorten it. This seemed like a lot of hassle, so I started to look for a better solution. After a visit to MPC (my local ural dealer), I discover this
Ural leading links use a rubber bush with a steel tube that is inserted into the rubber thus expanding it to fit. The rubber bush fits Unit forks and so does the steel insert, if you cut about 6mm off it.
So I duly bought two bushes and two inserts £17), cut 5mm off with a hacksaw and trued them up to the exact length on a lathe at work ( you could just file them) and fitted them yesterday. The links are not on the bike yet but the bushes seem to work fine. The metal insert is clamped solidly onto the swinging arm which can rotate a few degrees due to the rubber flexing inside the pivot tube, there is no sideways movement at all and they should last a lot longer than bearings.
Pushing the steel insert through was a lot easier than I expected, using a vice, WD40 and finally nuts, bolts and assorted washers. Both sides only took about half an hour. Now I know how to do it, it will only take a few minutes if I ever have to do it again.
The most time consuming part of the job was fitting my vice to the bench, which I have been meaning to do for years, that took me over an hour!!!!
2003 K1200GT Hedingham HUB Sidecar. RSP Top Yoke, RT bars, ABS/Servo removed, Klicktronic. EZS subframe, trail reducing kit and rear wheel. Wheelchair rack. Previous BMWs R80RT mono, R1100GS, R80RT (added a sidecar), R100RT sidecar, K75, K100 sidecar x2, K1100 sidecar, R1150R.

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Jaythro
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Postby Jaythro » Mon Oct 02, 2006 11:22 am

I would have stayed with bearings I think! But would have gone for taper roller rather than ball bearing

What you may find is by using the metal rubber bush type thingy is that the rubber/steel combination will restrict the rotating motion of the front "swingarm" and add a further restriction to the damping

On any of these I have worked on the front end needs to be free to move? in fact there was one that the caliper pivots had seized onto the spindle causing brown trouser effect at very moderate speeds, as the front hopped around alarmingly [-o< [-o< [-o<

If you hit a bump the spring / shock combination damps it if the arm moves freely but if the arm motion is restricted you may get chatter from the front?

Does the swingarm portion move free and easily when assembled and torqued up??
"Put your Ass on a motorcycle and ride with an attitude and the "Grim Reaper" will ride in your shadow!"

Islandmagee in case you're interested?

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Sofa
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Postby Sofa » Mon Oct 02, 2006 1:38 pm

The swing arm moves, but against the flex of the rubber i.e. the steel insert is fixed to the swing arm and the inside of the rubber. the outside of the rubber is fixed to the tube. It moves like it would with a really weak shock absorber/damper attatched. This is how the Ural one works and I am not aware of any problems with them. In fact the Ural ones are very similar to Unit ones except for the bush. The sidecar fed guys suzuki conversion works the same way and has been in use on a number of outfits for a few years with no problems.
Tubbs told me that the only reason Unit use bearings is that when they were first designed the just had some lying around. I have also been told that no other manufacturers use ball races..
Anyway once fitted I'm sure they will be better than forks.
2003 K1200GT Hedingham HUB Sidecar. RSP Top Yoke, RT bars, ABS/Servo removed, Klicktronic. EZS subframe, trail reducing kit and rear wheel. Wheelchair rack. Previous BMWs R80RT mono, R1100GS, R80RT (added a sidecar), R100RT sidecar, K75, K100 sidecar x2, K1100 sidecar, R1150R.

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Stitch
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Postby Stitch » Mon Oct 02, 2006 10:02 pm

I've never used rubber bushing in the fork pivots, but I've had Unit's bearings in the links on the GTR/XL for 14 years now, and 'aint had no problems.............................I just drop a spot of oil into them once or twice a year.

So far so good.............. [-o<

Cheers, Stitch.
Cheers, Stitch.
'07 BMW G650 XCountry (black/silver)
'02 BMW R1100RS SE (red)
'90 Kawasaki GTR1000 + Hedingham XL (metallic blue)
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BlondeMistress
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Re: leading links bearings

Postby BlondeMistress » Fri Sep 15, 2017 5:45 pm

Hi,
I'm having trouble removeing the cap on the left side of the leading link yoke, I've tried left and right hand rotation, its tight, but!! Anyone got any knowledge please?
R

King Herald
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Re: leading links bearings

Postby King Herald » Sun Sep 17, 2017 4:09 pm

Rubber bushes might well,take,out some 'road noise' too.

You'll find they are specifically designed to allow a certain amount of rotation too, so should be no problems there. I bet they only rotate a couple of degrees total on full wheel travel.
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