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Speed wobble(3 posts)

Speed wobbleWild Bill
Jun 12, 2002 3:47 AM
I own the new R5000 caad7 Cannondale. I have been riding it for over a month and I still have a speed wobble! It seams to be getting worse!
If I ride with no hands at 45k per hour I would crash!! On the down hills I have to hold on for dear life and hope there are no bends in the road. My LBS told me that it is too new and needs to be broke in..............I am scared that the broke part is coming true.
Can anyone help in this area? Is the headset to tight or to loose? Is it the TIME fork?
Wild Bill
Head set bed to be faced?tempeteKerouak
Jun 12, 2002 4:10 AM
I had similar problems with my Giant frame, and I know it happens with all type of frames...

i could hardly let go of the handlebar, the whole steering was harsh...

"It'll break in" or "too much roller wears the same spot"...

Then I had them reface the cups. And now I have a bike that handles like a dream; especially at speed. HS is a Cane Creek.

Your bike, like mine has a racing geometry that should feel more unstable at slow cruising pace than at 40 k/h. And it should track well at 70 k/h no problem. I actually discovered that my carbon fork and alu frame soaked bumps and tracked with confidence on a dirt road (76k/h)!!... I am 170 pounds. At slower (climbing, distance) pace, it is just another fine bike.

Check if the headset turns freely as it should -no friction.
Your bike is designed to shine at speed, and a carbon steering should only get better at high speed.

Get what you paid for.
Some info.Kerry
Jun 12, 2002 5:47 PM
The vibration of bicycle frames is a highly complicated event. In physical terms, your bike has a resonant frequency that is stimulated when you reach a certain speed. This is not uncommon. Without any hard data, I would guess that something between 10 and 25% of road bikes have this problem. Many riders never know they have it because it occurs at very high speeds or because they don't go no-handed at these speeds. There are lots of arguments about frame stiffness, the relationship between frame dimensions, forks, headset adjustment, wheel weight, bearing adjustment, etc. Some frames will never do this regardless of rider weight, wheel weight, adjustment, etc. Some will do it regardless of these factors, and some will do it only when a certain (unpredictable) combination of factors are in play.

Headset adjustment is often pointed to as a solution, because changing HS adjustment changes the "stiffness" between the frame and fork/wheel. A headset with fretted (dented) races should be changed, so if you have "index steering" you should eliminate it - this will allow the fork/wheel to move smoothly and therefore change the effective center of mass of the system. The weight doesn't move but if the wheel and fork have a different relation in space to the frame, this will shift the resonant frequency. Often changing tires or wheels also eliminates or triggers it. Within the range of things you can change easily, look hard at the headset and clamp your knees to the top tube when descending (changes the center of mass of the frame/fork). Some say they can defeat the oscillation by letting go of the bars, or holding them very lightly. Same logic about center of mass. You may have to accept that your bike vibrates, and just deal with it.