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General Help Section Members help each other here with tips and tricks about mods / maintenance and servicing based on their own experiences

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  # 1  
Old 20-05-12, 00:46
vadka vadka is offline
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Unhappy 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
  # 2  
Old 20-05-12, 06:07
googan googan is offline
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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
  # 3  
Old 20-05-12, 06:47
Petenz Petenz is offline
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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...
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  # 4  
Old 20-05-12, 10:52
Pleiades Pleiades is offline
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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.)
  # 5  
Old 20-05-12, 23:46
maxwell123455 maxwell123455 is offline
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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.
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  # 6  
Old 21-05-12, 10:48
uberthumper uberthumper is offline
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Tyre pressures can make quite a difference to whether a knobbly front will wobble at speed.
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  # 7  
Old 21-05-12, 16:44
SimonRoma SimonRoma is offline
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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
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  # 8  
Old 21-05-12, 17:47
mac-cos mac-cos is offline
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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.
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  # 9  
Old 21-05-12, 17:53
Dandy Dandy is offline
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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
  # 10  
Old 21-05-12, 20:40
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CaptMoto CaptMoto is offline
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Guys!!!

Let's not get tragic with your prognosys.

Vadka mate listen to me , 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.
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