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Nucleon- Front wheel wobble at high speed(6 posts)

Nucleon- Front wheel wobble at high speedAlexC
Aug 26, 2001 8:16 AM
Today I was speeding at 30MPH and the front wheel started to wobble and I had no choice but to slow down. My litespeed classic is equipped with Campagnolo Nucleon wheels and a Kestrel EMS Pro fork. I checked the wheel and everything looks ok. Does anybody have any ideas regarding the problem?
Not wheel inducedKerry Irons
Aug 26, 2001 3:19 PM
Unless the wheel is out of true or the bearings are loose (not likely in a cartridge bearing hub), the wheel is not the problem. Out of adjustment head sets are often fingered in this phenomenon, normally called "frame shimmy." In practice, any mechanical system has a resonant frequency, and if you excite the system at that frequency, you can get "destructive oscillation" where the vibration stimulates more vibration which stimulates more vibration, etc. Changing head set adjustment changes the resonant frequency of your bike and so shifts the vibration to some other speed and/or damps it effectively. Changing wheels or tires can have the same effect, as can shifting forward or backward on the saddle, clamping the top tube between your knees, grabbing the bars by the drops, the hoods, or near the stem, and so on. Some bike/rider combinations shimmy at the slightest provocation, while others never seem to. If it's any consolation, I saw one of the Mercury Viatel riders experience this problem as he raised his hands while winning a sprint. He quickly put his hands back on the bars!

The easy thing to play with is head set adjustment, and the easy way to control this if it starts is to clamp the top tube between your knees. The hard thing to do (apparently) is to tune the effect out of your particular set up. This is an oft-reported problem.
re: Nucleon- Front wheel wobble at high speedBirddog
Aug 27, 2001 5:29 AM
There is an interesting treatise on this at "damonrinard.com" click the appropriate sub head. Sorry, I am link challenged.
Try Thisgrzy mnky
Aug 27, 2001 10:50 AM
Wheels can be a source of highspeed problems - they can check out straight and true on a stand, but if the tension is all over the place then the wheel distorts in funny ways with load and at speed. Sometimes a computer magnet will throw the ballance off enough to set up and oscillation. The 30 mph range is characterisitc of this ballance problem - remember that a static ballance is not the same as a dynamic ballance.

Assuming that this is not the problem:

Try relaxing your grip on the bars. Often times people unknowlingly have a death grip on their bars. This is a significant factor in the high speed shimmy/wobble. Once you're aware of this you can see it for yourself by gripping things tightly then relaxing to see the effect.

There's really no reason why your bike shouldn't take you to 50 mph and beyond. The limit is usally the pedal/handle bar interconnect (i.e. rider).
Try ThisBreezydz
Aug 28, 2001 12:55 PM
I had this happen a few times with my Vitus 992. The last few times it started to shimmy I took my hands off the bars for just a few seconds and the shaking stopped. Letting go was pretty scary, but trying to stop the bike as it shook more and more was worse.
larger frame, right? >55cm or so?nm
Aug 27, 2001 12:11 PM
nm