Front-end shake under braking?

[Stevo]

I didn't know that about the disk gubbins/bobbins/goblins/nubbins - must clean mine. Perhaps I'll give em a squirt of chain lube or summat too..

Are you takin the Pess. Cos I'm not sure???? I wouldn't advise anyone to put chain lube there. As soon as the wheel rotates the centrifugal force would lube the disc and pads for you, even if care was taken not to put too much on. Could stop the shudder though

[F5 Dave]

Urine was being extracted 4sur.

I’d bet on disc run-out too. But it doesn’t take long for knackered discs to take out the steering head bearings making some tiny notches in the bearing shells. You can’t usually tell until you take the forks off & turn from side to side the notchy feeling destroys feel.

My RF had a brand new WOF & knackered discs/shot head bearings - it was super scary to brake hard on, but the bike was cheap enough so I rode it carefully home (5 min) & took it apart to fix before I was tempted to ride it again.

[NinjaBoy]

had a similar prob with the CBR but only really appeared on trackdays when braking hard at the end of straights etc...

The CBR had new steering head bearings and new fork oil.... I solved (or rather Frosty did ... and a few other things) by tightening the steering head nut. (1/8 of turn)

Steering became a little slower but soon got use to that.

[Brian d marge]

Don't know - but I would (confidently) guess never. Bike is 2001 model and has had 3 owners. According to the odometer it has only done 12,000km. Front tyre is Battlax BT54 (same on rear) which is probably original factory fitted jobbie. So 12,000km total mileage is probably right.

I doubt whether its a suspension problem.

Interestingly, my mate says he hasn't noticed the problem, to which I can only surmise he doesn't really use the front brake - like many others I fear!

Thinking about this , Is it when u use the front brake or when you roll off the throttle without using the front brake,???

If its when u roll off the throttle and start deaccelarating , my guess is the rear shock is either stuffed, or the spring rate , preload setting is wrong for you wieght.

so the rake /trail change when you get on the bike , but you mate doesnt notice. try altering the ride height bias( raising the rear by preload , dropping the front in yokes ,,I would jack up preload a bit ...) when you ride it and see if the problem gets worse or better

Sorry, this took a while but I was thinking about this in the morning and reminded me of this thread ..

If its ONLY when u use the brakes then its a brake /bearing problem loose steering head bearing etc

out of round wheels tyres will show up on a contant throttle ( accelarating and deaccelarating also but is harder to pin point )

Worn brake top hats will go clunk ONCE when you apply the brakes but stay in that position as long as the brake pressure is constant .

Just a thought

Stephen

Stephen

[Stevo]

So what have you found so far Rogson?

[rogson]

So what have you found so far Rogson?

Well, its been an odyssey.

Firstly, remember the bike is only 4 years old, has done 8,000km and had just got a warrant.

As I said originally I started-out suspecting the steering head bearings so tightened them about 1/8th turn. This reduced the shudder but didn't eliminate it.

So I told my mate (the owner) it must be the front tyre. He fitted a new one ($200) - but the shudder was still present.

So, I told him it must be the front suspension. We removed and disassembled the forks, cleaned everything and reassembled them with new fork oil ($15) - but the shudder was still present.

So, I told him it must be a warped brake disc (even though I didn't detect any pulsing in the lever). So, I spun the wheel while applying just enough brake to drag a little and found the pressure/drag was even through the whole revolution, and concluded it wasn't the brakes.

So, today I jacked-up the front wheel, strapped the rear end (including the rear suspension) down so there was no chance of movement other than at the front end and checked for play.

First thing I noticed was some (very small) play in the wheel bearings. So, I replaced them with new ones ($38) - play gone!

Then I checked for play in the steering head bearings (by pulling and pushing on the front end) yet again, and found a small amount (just perceptible) when the wheel was pointing straight ahead but none when at any other angle. I traced the movement to the top steering head bearing, so tightened it yet again until there was definite drag when I moved the bars from side-to-side.

However, when I checked again for play with the wheel straight-ahead there was just as much as before.

So, after all this I have concluded it is damaged steering head bearings!

I informed my mate of this, and told him we need to disassemble the front end and replace the steering bearings. Not surprsingly he seemed reluctant - I guess I don't have much credibility anymore. After-all, so-far the odyssey has taken over 6 weeks and has cost him around $250 - and we're still not home!

[TwoSeven]

Stearing head bearings are a bugger. Its so easy to overtighten them and easy to not do it enough. I recently cured a similar problem on my 600 - when I put pressure on the brake lever the bars bounced up and down. When the bike was still and I jumped on the bars - it felt fine. Went away when I pulled the steering head apart and did it up again (torque).

[rogson]

Sorry for resurrecting this thread, but the final outcome may be of use to someone.

I finally got around to removing the steering stem and checking the bearings - and everything was OK, apart from being dry.
So, I regreased it and put it back together making sure I torqued the stem nut "just right". I also took the forks apart and checked the bushings - again OK.

So, back together and - would you believe it - the front end still shook!

So, I was pretty sure I had eliminated the steering stem and forks - what could be the cause?

The bike has an aftermarket Givi windscreen on it, that is raked back (toward the rider) with quite a long unsupported screen portion. I noticed it shook up and down quite a lot, especially when braking or on rough roads - could this be it?

So, I went for a ride and held on to the screen when the road was rough and while braking and cornering, which seemed to improve things. So, I took it off, went for a ride and the front is now as smooth as...........

Come to think of it, some other bikes I have ridden with big windscreens have seemed loose in the front end to me - could it be the screen?

[Steam]

Nah, it's great when people resurrect old threads to tell what happened in the end. More people should do that, we want to see how things turn out.

As to loseness in the front end, front wheel discs (solid front wheels) also lead to that loose feeling, so that sounds right. It must be the wind resistance or something.

[Edbear]

[QUOTE=Steam;896990]Nah, it's great when people resurrect old threads to tell what happened in the end. More people should do that, we want to see how things turn out.[QUOTE]


Yup! I agree! Coincidence is a funny thing. I've just been on a 4-day jaunt and for the first time noticed mild headshake at about 70km/h. Especially if taken one hand off the bars. Thought it couldn't be tyre pressure, as I always check them before each ride. Had a WOF recently and no probs since then until setting off on the ride. Was thinking steering head bearings and plan to check them. Front tyre has done about 12,000km, (Metzler ME33), now and showing wear though plenty of tread on the edges...

Fork seals were done by the prevoius owner just before I bought it and he said he put heavier oil in them, I think 10w. and they're not leaking. Rear spring could probably do with a bit more preload, though, as I'm 93kg plus riding gear.

I always try to think about what recent changes were made in these situations and it could also be possible that my Brother-in-Law is to blame. You see, my first stop was to visit them and he gave me a full 4lt pack of oil that he'd bought just before selling his bike to help finance their new home. Adding it to the top box no doubt considerably increased the weight up high at the very rear of the bike. Mebbe I should go for another ride now it's all unloaded and see if the wobble's still present.