Bicycle Mechanics - Front End Bike Shake - Ksyzium SL on 2004 Cannondale R2000

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tandemnh
10-17-10, 06:40 AM
Recently on fast decents I have been experiencing front end shake on my 2004 Cannondale R2000 when going over 35 mph. The rim appears nearly perfect on my Part Truing stand. The bike is all original and to look at the bike it looks brand new as I keep up with keeping it cleaned, etc.

Any thoughts as to what may be contributing to the shake. I do way about 10lbs lighter over the past month or two as I have been eating better, etc.

Can the rim set up just be in need of a "professional" tune-up, maybe to tighten up the spokes/baldes? The do feel fine as far as I can tell.

What do you think?

kycycler
10-17-10, 07:48 AM
The problem may be in the head set a little loose. Try tightening the pinch bolts on the stem and the bolt in the center of the top cap on the stem.
dbikingman
10-17-10, 08:06 AM
the problem isn't a loose headset (well most likely not). Read here to for the problem and solution here (http://www.sheldonbrown.com/brandt/shimmy.html)

I know for me when it happened it was one of the scariest things I experienced on a bike and thought for sure I was going to crash.

PS It might be the wheels so send me your SLs and I'll send you a set of steel rims that have never given this problem.

tandemnh
10-18-10, 07:39 PM
I am not to sure about the article... my rims are in the mail!!:bang:
AEO
10-18-10, 07:42 PM
speed wobble, death wobble, shimmy, whatever your term for it, it's possible on vehicles like bikes.

a multitude of contributing factors causes it, but only one thing needs to be changed to stop it on a bike.
Either A: clasp your knees against the top tube, or B: lift your butt off the saddle or change your speed drastically, which will change the harmonics of the bike and cause it to stop.
tandemnh
10-18-10, 07:42 PM
I was doing 44 mph and it shook so had my bottles few out and my friends were preparing to pick up the pieces. But I did save it but I held on tight and held the wheel straight until the bike stopped shaking. It was quite the ride.

It happened a few weeks later at around 35 mph, so I need to figure out why be cause I love to ride fast.
tandemnh
10-18-10, 07:43 PM
speed wobble, death wobble, shimmy, whatever your term for it, it's possible on vehicles like bikes.

But the question is, how can you prevent it? Any tweaking of the bike? Truing of the wheels? What?