Front Fork Chatter Problem

[Paul996]

Having a problem with the S4R when heavy braking. Occassionally under heavy braking the front end chatters like mad. On some instances nearly shaking the bars out of my hand:o:o
I thought it might be the forks bottoming out so had the suspension sorted at the dealers. Front end stiffer but still get the issue.

It looks like the forks are vibrating front to back, not up and down.

Any ideas:puzzled::puzzled:

[Jools]

Warped disc on one side maybe? Could it be something to do with the tyre? Could it be that the rebound damping is too stiff and the forks are packing down? Could it be a worn fork seal? steering head bearings?

I would think that the forks are as rigid as a very stiff rigid thing (no s******ing) in the front to back direction and I would be surprised if the stanchions are flexing

[Edited on 23-7-2005 by Jools]

[Paul996]

It only happens on some road surfaces (rough) when very heavy braking. When it happened the other day and looking down on it, it just appeared to be flexing back and forth.

Was all right at snetterton, but then the surface is smooth.

Was wondering about steering head bearings or warped discs.

Was hoping someone else might have had the same issue and knows what needs doing. Not too comfortable with my local dealer:( always full of excuses why the job takes forever and he does not have the parts.

[sparkin]

Might be something simple like glazed pads,try taking the pads out and cleaning them with some abrasive paper,putting back in the same place.Did it happen before Snetterton?If it didn`t you probably glazed them on the trackday.

[rockhopper]

No way would you be able to see the forks flexing! Those upside downers are so stiff that a front end crash is more likely to bend the frame than the forks.
I wonder if the front wheel could be locking up under the heavy braking you mention?

[psychlist]

Check your fork settings are factory "standard" and if that doesnt help try backing off the preload one ring, on both fork tops, obviously ;)

[Paul996]

I had the problem before and after snetterton, so not sure about the pads.

Had the forks on standard setting and it was worse, slightly better now it's been stiffened up.

Going to send it back to dealer and let them sort it under warrenty:mad:

[Lee1980]

I used to get a feeling on my 748s which has the same set up as the s4r, when i was coming to a stop it would almost feel like the pads were slipping on the discs and it would be worse in the wet.

Also my 748s which has the same forks as my s4r, felt like to me like loose head bearings, but dealer insisted it was movement between the stanchions inside the fork outers, as i rocked back and forth mainly it happened.

[AK]

Just an idea.... some monsters have plastic rebound spacers, which have been known to break - might be worth asking your dealer to check them for you.
(but he'll only be able to see when they are apart, so needs a full strip down)

Try a ride with a plastic tie round one of the fork legs, and see what travel you are getting. See if it is going to the bottom.
If so, we had this with the race bike, and had to increase the preload to stop this juddering as the tyre was taking all the impact of the hard braking.
This is quite extreme tho, and NOT a common occurence.

CK had a prob with the headbearings tightening up on her bike recently, so much so, that they caused a spill on a tight turn. Never heard of it before, and if i didnt check the bikes myself, I'd have never have believed it.

Do double check the tyres tho - and maybe get a good tyrefitter to do this for you too

Alan

[Paul996]

Cheers all:)