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Bike Shaking at High Speeds

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Bike Shaking at High Speeds

Old 06-23-09, 06:20 AM
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Bike Shaking at High Speeds

I was racing this weekend (my first tri race) and the finish had a long steady hill so I let go and started riding as fast as I could when My bike started to shake out of control. Lucky for me the hill evened out before I spilled. (almost went head on into a car)

This happened to me before going 50MPH on my mt bike years ago so I knew not to slam the brakes.

I applied the brakes lightly and there didn't seem to be a distortion on the rims.

HELP!!! I'm thinking maybe a mis match of stiffer fram with flexable forks? Does anyone have any Idea regarding how I might prevent this from happening again? I like to ride fast!

Brand new Cannondale CAAD 9 frame set
Brand new bontrager race lite wheel set
Brand new tires (continential sport)
cannondale brake set
Cannondale chain rings (53/39)

k-force carbon FSA bars 44
- Durace Ace 7800 BB, cranks, shifters, cassette
chain rings are Cannondale).
Controltech stem
Carbon USE Alien seat post
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Old 06-23-09, 06:31 AM
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High speed vibration has long been a problem on light road bikes. It's been blsamed on frame alignment, wheel trueness, tires, you name it.

The reality is that it's a harmonics problem and an individual characteristic of your bike. Unfortunately there's no bulletproof mechanical cure.

When coasting down hill at high speeds, keep yourself in a small tuck with the cranks horizontal and your knees in, all of which is good basic aerodynamics. Now since they're in anyway, press one or both knees against the top tube. This will change the harmonics and dampen or prevent the vibration.
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Old 06-23-09, 07:51 AM
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50 mph on a MTB ...? seriously? cough cough

about the high speed shake - look up "death wobble" it's a phenomenon and the cure is to lower your center of gravity, by getting up on the pedals and grabbing the frame with your knees. adding a little weight to your front wheel via your arms and handlebars will help too. there is nothing wrong with your bike. sometimes it's a tiny thing that can set it off.
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