Very scary wobble?

[tallspinboy]

I have experienced a very scary steering wobble and I need to know how to address the problem before I have an awful accident.

I have a 2005 Cannondale R1000 with a carbon Slice Premium fork and Ksyrium Elite wheels. On 3 occasions I've been riding down very long descents at over 35 miles per hour and have experienced a "wobble" that threatens to put the bike out of control and me onto the pavement. I've just been lucky each time that there's been no one behind me. It seems to start as a slight steering misdirection and progresses until the handlebars are moving violently backwards and forwards about 2 to 3 inches. These episodes last about 30 seconds and the resulting shake is drastic enough that my waterbottle is thrown after about 15 seconds. I have avoided going down by gripping the brake hoods and using my rear brake until I can come to a complete stop.

I count myself as more than lucky so far. Please help!

 

[Insight Driver]

Take it to the dealer and start swapping things out, one at a time. There are a lot of reasons a shimmy starts on any particular bicycle. A process of elimination will nail it. You already have repeatable conditions which inititate it. As an experiment see if someone else can ride your bike down the same hill. A different rider could make a difference. It is not just the bike, but the interaction between the bike and rider. One without the other will not cause a shimmy problem, if you get what I mean.

 

[slide]

Does it happen EVERY time when you exceed a certain speed?

IIRC, Sheldon has some interesting entries on wobble.

 

[gclark8]

Easy to check these yourself:
tyre fitted correctly, correct rotation, even rim tape,
the manufacturers mark on the tyre at the valve,
the big orange reflectors removed from the spokes,
no patches on the tube,
check the wheel balance,
check for true, both axis,
check brake caliper is centre.

 

[mikesbytes]

I have a 2005 Cannondale R1000 with a carbon Slice Premium fork

In addition the the advice above. Have you changed the forkes? This problem can also be caused by reducing the trail, which could happen when a different set of forkes are put in. If you have the origional forks, I would suggest that you try putting the old ones back in.

 

[karries]

See the thread on noodly feeling experienced on a giant. I have a schwinn and actually crashed because of this wobble/noodly feeling when decending.I hope we can solve this.

 

[60ish]

One easy thing to check: when you clamp in your front wheel before a ride, do you check the front brake clearance on both sides of the wheel. If the brake pads are not the same distance from the rim, your front wheel will oscillate while braking at high speeds.