HELP!! Unstable bike at over 65 mph
 

Hi Guys,
need some help. My bike becomes very unstable when I go over 65-70mph, font wheel starts wobbling and handlebars start shaking. To see what happens I increased my speed to 80 and bike becomes almost impossible to handle. The closest description I can give, it is very similar to when you puncture you front tyre and bike starts zig-zaging??? (closest synonym???). First I thought It was my forks as one was leaking oil. But mechanic sorted that out and problem still there. Also the front wheel has been balanced bearings are fine too. I have knobblies on my wheels, but they are in good condition. Think I only done about 2500miles on them. Middle ones are a little bit more worn than side ones.
If slow down to 60 and less. Bike is fine, but my confidence is going even on short rides. Any suggestions?

Thanks for your help.

Just in case here's a link to the tyre photo

https://picasaweb.google.com/lh/phot...eat=directlink

Vadims:120:

Wheel wobble
 

A mate of mine had the very same problem, it was related to the tyre.
He was describing his....similar to a tank slapper.
It just seemed to correct itself after a good few miles.
I know he never changed anything although he did put some slime in his tyre to prevent punctures and that may have corrected the problem.
I do know it did not help him when riding the bike.
Hope this helps

steering head bearings lose... spoke tention..wheel balance..'front & rear"
Another place people don't look is fork springs..If one has lost its tention it will put more load on the other causeing the wheel to sit slightly side ways....swing arm pivit...
dose the wooble change between on the power / off the power?


I had lose spokes on a RD350 rear wheel years ago... I couldn't slow down..under power the rim tracked straight...Off the power the rear went evertwhere.. Only way I could slow down was lock the rear wheel up with the brake..if it wasn't turning it wasn't a prob...

In addition to the above...

Have you got the basic suspension settings correct? Too much sag/too little preload (or a knackered shock spring) at the rear will cause bad headshake, more so at higher speeds where the wind acting on your body transfers more weight to the rear. A lot of high speed wobbles and tank slappers can be sorted by getting more weight over the front, add preload to shock, raise the fork tubes through the yokes 5mm at a time. Too little sag on the forks and too much front rebound damping will have the same effect (although this is less likely in your case, unless that is you've changed things up front (fork spring spacers, more viscous oil, changed the air gap etc.)

First of all what miles has your bike got?

How many miles has your front wheel been on for?


First off when your front tyre wears it doesnt wear evenly so will wobble a bit but normally you will not notice this untill its quiet big like yours is now. If a wheel weight comes off it will give you the same feeling but very instant change. Or if your head race bearings are worn so much this will also give the same effect but this takes a good lot of miles or failed wheelie attempts to wear them out.

Tyre pressures can make quite a difference to whether a knobbly front will wobble at speed.

Yeah you gotta go through all of these points one at a time till you get the bike going straight again, will probably be something very stupid and you will kick yourself.....so take your time and always ONLY change one thing at a time and write it down, so you can always go back if you need to!! Good luck xxx

Check the simple stuff 1st and as has already been posted, Tyre pressures. What works off road may cause huge instability on road.
K60s on my S10 need over 30psi front if they arent to get wobbly at the national speed limit. Stick them at oem pressures and ride it to see what effect they have.

Get the same on my xtr at over 80mph I have Metzler Karoo`s and I just dont think they are designed for high speeds on tarmac

Guys!!!

Let's not get tragic with your prognosys. :blahblah:

Vadka mate listen to me :whisper:, take your pressure down to 29-30 psi on the front tyre and never over 33psi unless you are a really large fellow.

Rear tyre 33psi ALWAYS.

The end.

I had the same problem after some ****** reversed over my bike dragging her down the street....after a while she didnt like to turn left (roundabouts become rather fun). Changed the headstock bearing and now fine. Thats what my money would be on.

I've had the same wobble for ages. Because I rarely use the bike on fast roads I've put up with it.
I noticed when up the Lakes recently, hitting some of the slightly larger bumps offroad I heard a definate knock, but I'd never noticed before even taking speedbumps at a fair pace.
Then after my journey back from the Lakes I sat on the sofa and could still feel the weavy wobble. Enough's enough.

So after correcting my tyre pressure, as recommended above (I was running 28psi in both) and then a steering bearing regrease, ensuring it was as tight as I could get it with no drag on the steering.....
...All seems better. I may have even recently sailed through a camera slightly faster than planned as I thought I was going slower Doh.

So in my case it was very slightly loose head bearings and a rear tyre 5psi too low, front2 psi too low. I appreciate some folk have different size wheels to me.

XTX with distanzias.

Although in my last post for this thread I seemed happy, honestly I've never thought it is quite how it should be.

Think I've sussed it,
I went for a ride today without the front mudguard. The beak.
A quick blip at some faster speeds and all seems sweet.
I don't know if this is pointing at something else wrong, but there's not much it could be.
The bike is nearly six years old with original suspension springs, about 29k.
I've replaced steering bearings again since last post and changed fork oil.
I can't feel any play in the front wheel bearings. I guess that means they are OK?

Think I might invest in a low mudguard of some description.

I had my bike serviced today
I did had a wobble at 65 but now its worse at 65 i pulled the bars tight and it settled down the faster i went the harder it got the guys have pumped my tyres up will check psi when i get home and adjust will reply and see how it is

I am fitting hyperpro springs kit it has a thicker oil too the front forks on the xt are way too soft ::


Xt660x 04

Time perhaps for a gentle service of the front end suspension ie change fork oil and fit Kev spacer will help????

Asked kev about the spacers there no longer available :/ hyperpro do a springs kit with oil �115 thats my next mod :)


Xt660x 04

Just lower the pressure to 28psi and you will send me a check of �xxx as a thank you muchly! I guarantee you.

Its the sag i dislike mate and also the sudden drop of the front when breaking i come from a enduro. Background and like a rough ride :) lol


Xt660x 04