Front Wheel "Chatter" - WTF?

[Nemo]

Whilst proceeding at an enthusiastic speed along a stretch of Dual Carriageway my front wheel started to rapidly oscillate up and down. It wasn't enough to cause me to lose control but the vibration was so bad that I thought the instrument binnacle would bounce off. Slowing to a more reasonable speed stopped it. Then onto some motorway where I noticed that it would start again if the surface changed or there were some bumps. Speeding up as well as slowing down stopped it. Honestly officer!

Everything appears tight. No top-box. I do use Ultraseal but in 1000s of miles of use I've never experienced anything like this. The balance weights are still on the wheel. I have hyperpro springs (not the short ones) front and rear and the suspension (sag etc) was set up by a professional. http://www.mhracing.com/

So I'm a bit lost on what to do next? If anyone has any ideas I'd appreciate it before I head off to Scotland from Reading in late June.

Thanks,

Nemo

 

[ghiribizzo]

Calipers off first and try a 'balance'. Does it pendulum down to a heavy spot? Is the wheel mis-shapen? Okay revolving by hand but out of balance dynamically at speed? Are the bearings in good order?
Mmm. Damping settings?

 

[Nemo]

Fault found

First off thanks to ghiribizzo for the reply. I do appreciate it when people take the time to respond to a question. And sorry to bother you!

Decided to look at the bike again and feck-me but the front damper is covered in oil and it's dripping onto the floor. Looks like a seal in the damper is gone.

I now have until 16 June to get this fixed (MOT & trip to Scotland) and if anyone saw my thread about the last time I f*cked up my suspension they'll realise this isn't easy for me! (cue Mission Impossible theme music).

Do I buy a new BWM damper (not the best) or replace both units as a matched pair - the Ohlins or whilbers route.

FECK!!!!!!!

Nemo

 

[Zigo]

Sorry about your mishap. Saw in a Norwegian forum that one of the members had the same problem as you with a blown damper. I think BMW wanted to check his damper as according to them this was an unusual occurrence. Maybe not?
As to new dampers, I changed the original set with matched Wilbers about a year ago. The bike now handles with confidence whatever bad roads and curves it tackles, recommended!

 

[Magwych]

Nemo, what springs to my mind is whether the front damper is the cause or result of the problem It could be a wheel out of balance causing excessive vibration, and that vibration could cause a premature failure of the shock. The balance may still be there, but are they correct? After a few hundred miles the balance of tyres can change. I have no idea if you have wire or cast wheels, if the former it is not unknown for them to go slightly off true.


Worth checking the balance of the wheel whilst you are changing the shock? It took a hie to get my Wilbers set up as I like them, but once sorted they are well worth it.

 

[Nemo]

Thanks

Thanks Zigo and Magwych for the advice about wheels/wilbers etc. I'll certainly check out the wheel (cast) balance issues.

Nemo

 

[paul nicholls]

vibration.

may well be the shock infact prob is if the damper is shagged.
but! i had exactly the same symptoms on my old zx9r and it turned out to be the puncture seal forming a hard clump in the tyre. i tried the wheel ballance, head bearings and suspension before finding the problem.