Ultegra front brake calliper

[Gooch]

This is a weird one. I've only ridden my new bike twice but each time I build up speed to go down a steep hill my front brake comes on of its own accord. I'll look down at the calliper and see the brake block rubbing on the rim and the whole bike vibrates. I then brake to a stop to see what has happened. As I begin to a slow almost to a stop, it releases.

Now I could understand it if I put on the brakes and they then locked to the rim, but I'm not actually touching the brakes. They are coming on on their own. It can be a bit embarrasing when you're ridiing with other people because they just think you've bottled it on the descent. I gonna wip the front wheel off later and put plenty of lube around the calliper to see if this helps. The calliper itself is not loose on the forks so I can't understand it. I've never come across anything like this before. Anyone else? B)

 

[summerdays]

If its new - take it back to the shop... you haven't turned the handlebars 360 degrees have you?

 

[Gooch]

If its new - take it back to the shop... you haven't turned the handlebars 360 degrees have you?

No I haven't.

 

[Gooch]

After further examination it seems that it is not the brakes at all causing the problem. I just assumed it was the brakes at first because the noise and vibration's felt exactly the same as you get some times when braking hard in the wet. It seems that the noise and vibration is coming from the area of the bottom bracket. It happens at random intervals but more so when I'm gaining speed on decents. I then put the brakes on and just about as I am about to come to a stop the noise and vibration stops. The bike is going back into the shop this week for further investigation.

Has anyone else experienced anything similar?

 

[gwhite]

What you seem to be experiencing is probably frame shimmy. This is caused by the frame resonating at certain speeds or can be caused by having the rear panniers too far back from the centre of gravity of the bike. Sometimes it can be cured by pressing your leg against the top tube of the bike and sometimes the application of the brakes can help. To verify this try the knee against the top tube.

 

[Gooch]

Thanks for the advice gwhite. If it is frame shimmy what can be done to resolve it? I've only had the bike a week and it cost me an arm and a leg.