What causes my vibration???

[sirroada]

Ok, I have a 2005 legend Ti. The michelin tyres have 300 miles on them. I have a DA 10 set up with Ksyrium SL's. So here is my question. Whenever I get the bike over 25 mph I get a vibration in the rear triangle that I feel in the seat and pedals ONLY. It is a "buzz sensation". The faster I go the more buzzy it feels. I don't feel usafe while it is doing this but it sure is annoying.
I had the rims checked, they are straight and true. When I spin them while holding the wheel in my hands it oscillates up and down a little bit (this is with the tyres off the rim). Once the tyre is on the rim the oscillation goes away. However, when the wheel and tyre is on the bike and I spin it up on my stand in a real high gear I get that oscillation. What could be going on....?? :confused:

[JohnS]

Ok, I have a 2005 legend Ti. The michelin tyres have 300 miles on them. I have a DA 10 set up with Ksyrium SL's. So here is my question. Whenever I get the bike over 25 mph I get a vibration in the rear triangle that I feel in the seat and pedals ONLY. It is a "buzz sensation". The faster I go the more buzzy it feels. I don't feel usafe while it is doing this but it sure is annoying.
I had the rims checked, they are straight and true. When I spin them while holding the wheel in my hands it oscillates up and down a little bit (this is with the tyres off the rim). Once the tyre is on the rim the oscillation goes away. However, when the wheel and tyre is on the bike and I spin it up on my stand in a real high gear I get that oscillation. What could be going on....?? :confused:
Unbalanced wheels?

[Smiley]

Try another wheel set and rule the wheels out for sure , its that simple

[stevep]

smileys right.

[Sandy]

First, remember that my knowledge is minimal as compared to most on this forum, but I will give this a try.

If you look carefully at your rim, you will see a little seam on the rim directly opposite the valve stem. The weight of the rim at this point is different (heavier) than at other points on the rim. The oscillation is caused by the difference in the weight of the wheel at the valve and at the seam. I think that if you try another set of wheels you will also find some oscillation. I add an extra nut to the valve stem to help offset the weight at the seam. I don't think that there is anything wrong with a wheel that oscillates in a work stand using a high gear. It doesn't mean much since it will not oscillate on the bike with the cyclist's weight. Of course there might be a problem with the wheel that might cause undue oscillation and possible vibration. There might be other causes too.

Maybe there is something significantly wrong with the wheel, so changing the wheels seem like an excellent idea. It certainly could be a wheel problem, I think. But maybe not.

As I said, I don't have the biggest brain on the forum, so what I just said may mean very little, or nothing at all.


Sandy

[William]

...As I said, I don't have the biggest brain on the forum, so what I just said may mean very little, or nothing at all.


Sandy

That would depend on where your "brain" is wouldn't it Sir Sandy??

http://tell.fll.purdue.edu/JapanProj/FLClipart/Verbs/sit.gif


William ;) :D