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stkman

4RT linkage bushes ...

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Hi All,

I replaced all the linkage bearings in my 4RT when I first purchased it used ... since then have dismantled and regreased every six months. All well for almost 4 years but noticed play recently. Found 1 set of bearings good, one OK and the third rusty and seized. Rather than replace more bearings, I thought I would try some bushes a local (relatively) trials riding engineer makes up. The plastic bushes are made of a self lubricating hard plastic (used for bearings in industry) and the collar that slides inside the bush is stainless steel. I put it all together with lots off grease and the large o-rings look like they will seal it all quite well.

The whole setup looks a lot simpler than the original setup ... rear suspension feels great now and hopefully maintenance will be simpler. Will see how this setup works.

Original bearing setup on left, bush setup on right.

4RTlinkagebearings.jpg

Andrew

Edited by stkman

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Hi All,

I replaced all the linkage bearings in my 4RT when I first purchased it used ... since then have dismantled and regreased every six months. All well for almost 4 years but noticed play recently. Found 1 set of bearings good, one OK and the third rusty and seized. Rather than replace more bearings, I thought I would try some bushes a local (relatively) trials riding engineer makes up. The plastic bushes are made of a self lubricating hard plastic (used for bearings in industry) and the collar that slides inside the bush is stainless steel. I put it all together with lots off grease and the large o-rings look like they will seal it all quite well.

The whole setup looks a lot simpler than the original setup ... rear suspension feels great now and hopefully maintenance will be simpler. Will see how this setup works.

Original bearing setup on left, bush setup on right.

4RTlinkagebearings.jpg

Andrew

Looks good to try! Just got to see if it holds up! There is a lot of science behind bearings and bushes, perhaps this plastic will work, or you could go to bronze. Seeing the sherco go to a plain(steel) type bearing was of interist.

Friction, sticksion, loading and wear along with corrosion all come into play here. I really wish we had more bearing engineers chime in on this!

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Looks good to try! Just got to see if it holds up! There is a lot of science behind bearings and bushes, perhaps this plastic will work, or you could go to bronze. Seeing the sherco go to a plain(steel) type bearing was of interist.

Friction, sticksion, loading and wear along with corrosion all come into play here. I really wish we had more bearing engineers chime in on this!

The Honda CBX 1000 (6 cyl) had plastic (or teflon) swingarm 'bearings', that was (one of) his weakest point (Also rubber forks and frame). But that was in the eighties (??)

I guess technologies have improved since then... :)

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The standard bearings are Full Compliment needle bearings designed to work under heavy load. I'll be interested to see how your experiment goes. Keep us posted.

Edited by for artie

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The standard bearings are Full Compliment needle bearings designed to work under heavy load. I'll be interested to see how your experiment goes. Keep us posted.

Technically the O rings will drag considerably more than the standard seal, they are made for static sealing situations like an inlet flange etc. Still will be interesting to see how it works over time.

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Not sure drag going to be an issue when hitting a step flat out in 3rd with a 14stone rider. I think localised pressure is going to be the big issue. Mechanical advantage must mean that the PSI or KGMM2 at the actual bearing point must be big. Hence hardened bushes/needle rollers as std. Trouble is needle rollers are better suited to a some sort of rotation which is not seen in suspension.

Good luck with experiment as good mods are worth while.

I know some people offer sealed for life linkages - be interesting to see whats in them.

Best solution I've seen was mono Yam - called grease nipples - grease every week - grit out, fresh grease in!!

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Hi All,

When assembled on the bench, the o-rings barely touch the bushing sleeve - the engineer that makes these parts told me to get the bush exactly centred in the dogbone or swingarm so that the o-rings aren't compressed. In fact, the setup came with an installation tool to get the bush centred exactly.

I will judge how well the bush is standing up to the forces by judging the amount of play at the rear wheel. The bushes will be relatively cheap ... even if they last only six months of weekly riding, I'll condsider this setup a success.

Will report back in 6 months or sooner if this setup fails.

Andrew

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"Keep us posted.'

and

"Not sure drag going to be an issue when hitting a step flat out in 3rd with a 14stone rider. I think localised pressure is going to be the big issue."

And here's another set of 'plastic' linkage bushes going in to a 4RT. The bushes on Stkman's 4RT seem to be working out after almost five months of constant use. So when the bearing failed on mine (localised pressure applied by a gnarly old tree root in Section 6) I opted to use the same type of replacement. They came as a set of three with O-rings and with an installation tool as suppled by 'www.blaymiresengineering.co.nz'. Peter at Blaymires has been using them in his own Repsol. Cost is about 60% of a new tyre or 60% of a new set of fatbars.

Photo of my newly installed bushings is below. Note compression damage on the outer edge of lower (rear) dogbone. Photo makes it look worse than it really is. The damage is to one corner only and no doubt the impact or blow was what did in the original bearing. A thicker and longer bash plate - of the sort that H&D sell - will be on my Xmas list. But I don't expect the wife will take the hint.

IMG_1173.gif

Edited by Ross Brown

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I know this is an old topic but how have the bushing faired long term. I took my bearing sapart to lube today and 2of the 3 are trashed. I think a good bushing might be te answer especially sine I ride is lots of water and mud.

Edited by brianjonesphoto

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I'm curious how the bushes stood the test of time and abuse...

I think broze bushes or needle bearings with grease nippels (to lubricate but also to keep the dirt out) should last very long.

If I wanted to improve the rear suspension bearings I would install grease nippels...

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What I have found for lubrication that lasts for a season or more is to simply use a very sticky chain lube on the stock needle bearings. Let it dry and reapply a few times. Then coat the plane bearing surface with waterproof grease as well as the dust seals. This keeps the water out, and the chain lube saturates the needle bearings better than grease can. These needle bearings have no real open space inside to hold enough grease.

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I'm curious how the bushes stood the test of time and abuse...

The bushes that went into my 4RT are 18 months old now. Still good. Mind you I haven't been whacking the linkage into tree roots of late.

Edited by ross brown
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I'm curious how the bushes stood the test of time and abuse...

My 'plastic' bushes have now been in for almost 2 years - around 250 hours riding - with no maintenance whatsoever and I am about to replace one sleeve as it is showing a bit of play. The others are perfect. A lot of my riding is in sandy conditions and am wondering how much sand managed to find it's way in.

Will take photos of the 'old' bush and post.

The actual 'plastic' used is Acetal (polyoxymethylene) which I suspect is far more suitable in this application than nylon ...

Andrew

Edited by stkman
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I recently made a chain tensioner blok from the green plastic Ertalon LFX which contains oil, in other words is self lubricating.

So far it doesn't look so good, it wears faster than a standard "rubber" chaintensioner...

But it's working conditions are ofcourse worse than the link bushes.

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