replacing linkage bearings

1209 Views 9 Replies 3 Participants Last post by ukzx10r, Feb 16, 2017

JohnnyB

Discussion Starter · Feb 10, 2017

This is a question for the wise and widely travelled suspension guru types

I just replaced all the bearings/seals/inners in my linkage using OEM parts.
While going through the process of installing a different shock i had noticed there was some up/down play in the rear wheel when the rear wheel was hanging, not much but it bugged me enough that I wanted to replace all the moving parts.
I used a 12mm high tensile bolt and various sockets to press out the old bearings and push the new ones in, no problem there and I didn't have to remove the swingarm like the manual says to do.
Anyway, here's the thing. With all brand new OEM parts there is still a tiny bit of up and down play when the rear wheel is hanging, only a couple of mm but it's there. The play seems to be mostly in the pivot point for the linkage on the swingarm. I can just feel it moving with my finger stuck in there.
So....is this normal???? Is it ok?
Is there a better option than OEM...upgraded bearing?? using two shorter bearings????
Would really appreciate some enlightenment

P.S. I realise that these are high wear components and there is a lot of stress on the linkage bearings, which don't actually appear to be that big considering the job they perform. The bearing at the linkage pivot on the swingarm seems to me to get a good old hammering.

Save

1 - 10 of 10 Posts

ukzx10r

· #2 · Feb 11, 2017

Yes this is normal. Its always bugged me too but what you have to remember is 0.1mm at the bearing equates to alot more at the rear wheel.
Plus the only time this movement would be apparent is when shock is completely maxed out. (Wheel off the ground).
All other times the spring force is so great that it keeps load on the bearings even over ripples in the road

Save

JohnnyB

Discussion Starter · #3 · Feb 12, 2017

Hmmm. yeah thanks that was kind of what i was thinking. Tiny bit of movement at the bearing equates to a little bit at the wheel. Plus there are a number of pivot points which all have that tiny bit of play. so there's a cumulative effect also.
I guess this would be more of an issue with dirt bikes where the bike is often off the ground.
Anyway, the amount of play reduced quite a bit with the new bearings so it was a worthwhile endeavor.
The other thing, is that it's suggested in many places that when setting sag you should measure unloaded height with the rear wheel off the ground and hanging, so this freeplay will be added on to your measurement. When you get riders speaking of differences in ride height etc of a couple of millimeters it just makes me wonder.........if you are using the fully extended measurement as a reference to set heights anyway.

See less See more

Save

evallarta1

· #4 · Feb 14, 2017

You're always going to have play. The other thing to take into consideration is the bolts going through the linkage/shock. Because the bolts don't fit tight there will be slop.

Also dont get hung up on exact sag numbers. Use them more as a guideline instead of gospel.

As to setting ride height, I don't know why you would measure it any other way except fully extended. If you measure it with the tires on the ground you will never get consistent, accurate measurements.

Save

JohnnyB

Discussion Starter · #5 · Feb 14, 2017

evallarta1 said:
You're always going to have play. The other thing to take into consideration is the bolts going through the linkage/shock. Because the bolts don't fit tight there will be slop.

Also dont get hung up on exact sag numbers. Use them more as a guideline instead of gospel.

As to setting ride height, I don't know why you would measure it any other way except fully extended. If you measure it with the tires on the ground you will never get consistent, accurate measurements.

Thanks Evallarta!

Sure, of course you have to measure at extension, I was referring to how some just tilt the bike on its stand to get an extended measurement, which won't be quite the same as jacking the bike up and having the wheel hanging. In fact I know I had a different figure between those two methods. The only time I noticed the play however was with the bike jacked up.
Also, those bearings definately wear relatively quickly (my bike had only 15k klms on it) as there is a lot of load on them from what I can see, and on the gen4 anyway there is pretty much zero protection for the linkage from the hugger so it cops it from road gunge. When I first disassembled my bike the linkage was full of grit and crap. When testing the old bearings I could "feel" the rollers falling into slight indentations in the inner sleeve at one particular point of rotation.So the measurement at fully extended will change by a couple of mm when they wear. As i said earlier the play in my rear wheel was reduced markedly by installing the new bearings.
Incidently, the gen 5 has bearing seals with a flange on them so the seal flange prevents a lot of crap getting into the gap between the linkage plates and dogbone/swingarm boss. Seems better to me.
As for the mounting bolts.....Surely with them tightened to correct specs they are clamping the inner bearing sleeve against the linkage plates/swingarm boss/shock mount and...once settled, the inner bearing sleeve shouldn't move around? Mine don't certainly.

See less See more

Save

Reactions: 1

evallarta1

· #6 · Feb 14, 2017

JohnnyB said:
Thanks Evallarta!

Sure, of course you have to measure at extension, I was referring to how some just tilt the bike on its stand to get an extended measurement, which won't be quite the same as jacking the bike up and having the wheel hanging. In fact I know I had a different figure between those two methods. The only time I noticed the play however was with the bike jacked up.
Also, those bearings definately wear relatively quickly (my bike had only 15k klms on it) as there is a lot of load on them from what I can see, and on the gen4 anyway there is pretty much zero protection for the linkage from the hugger so it cops it from road gunge. When I first disassembled my bike the linkage was full of grit and crap. When testing the old bearings I could "feel" the rollers falling into slight indentations in the inner sleeve at one particular point of rotation.So the measurement at fully extended will change by a couple of mm when they wear. As i said earlier the play in my rear wheel was reduced markedly by installing the new bearings.
Incidently, the gen 5 has bearing seals with a flange on them so the seal flange prevents a lot of crap getting into the gap between the linkage plates and dogbone/swingarm boss. Seems better to me.
As for the mounting bolts.....Surely with them tightened to correct specs they are clamping the inner bearing sleeve against the linkage plates/swingarm boss/shock mount and...once settled, the inner bearing sleeve shouldn't move around? Mine don't certainly.

Sounds like you got it under control! And the slop I was talking about was the gap between the bolt and the bearing sleeve. Like you mention you shouldn't have any play between the bearing sleeve and the bearing, otherwise you got bigger problems!

And when taking measurements for geometry a little trick is to push down on the tire before taking a measurement. If the suspension has a topout spring it can manipulate the measurement. You want the topout completely compressed to give you the consistent numbers. And I know what you mean about the half-ass attempt to get a measurement lol.

Save

JohnnyB

Discussion Starter · #7 · Feb 14, 2017

Thanks again "E"! yeah you guys have addressed my main concern which was the play in the linkage. Thanks very much!
I'd love to know if MotoGP bikes still have this amount of play in the link, those guys can feel every nuance I'm sure and in their case the rear wheel is indeed often off the ground under brakes......

Save

ukzx10r

· #8 · Feb 15, 2017

Bolt play has no effect on anything as they just clamp everything together so the sleve and bearing are the only factors when you find play.
I noticed the gen5 has bigger seals too as i have a set here.
Better seals will increase life span for sure.
I expect motogp bikes would use a bearing and guide with a higher tollerence with less play but that would cost alot more. Worn bearings will increase the sag numbers yes but youd need alot of sag to make a noticable difference

Save

Reactions: 1

evallarta1

· #9 · Feb 16, 2017

ukzx10r said:
Bolt play has no effect on anything as they just clamp everything together so the sleve and bearing are the only factors when you find play.
I noticed the gen5 has bigger seals too as i have a set here.
Better seals will increase life span for sure.
I expect motogp bikes would use a bearing and guide with a higher tollerence with less play but that would cost alot more. Worn bearings will increase the sag numbers yes but youd need alot of sag to make a noticable difference

I would agree with you that side to side play there would be no play due to the bolt clamping everything together. BUT there can be vertical play between the bolt and the sleeve.

Not really sure how worn bearings can increase sag, care to elaborate?

And like someone else mentioned when the bike is loaded the slack/play is taken up and it not an issue when in motion. And even if you WOULD feel it when the suspension is fully extended it would probably be misinterpreted as a bump or imperfection in the road.

Save

ukzx10r

· #10 · Feb 16, 2017

evallarta1 said:
I would agree with you that side to side play there would be no play due to the bolt clamping everything together. BUT there can be vertical play between the bolt and the sleeve.

Not really sure how worn bearings can increase sag, care to elaborate?

And like someone else mentioned when the bike is loaded the slack/play is taken up and it not an issue when in motion. And even if you WOULD feel it when the suspension is fully extended it would probably be misinterpreted as a bump or imperfection in the road.

The bolt does not move inside the sleve once tightened up. Effectively you could have a smaller bolt inside the sleve and it wouldnt create more play in the linkage if you catch my drift.
The side plates clamp the sleve and basically create one complete part that moves around the bearing.
Its easy to think that it would though as i did too until i actually started experimenting with links

Save

1 - 10 of 10 Posts

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.

Top Contributors this Month