Originally Posted by
Dawes-man
Very common. The problem is the clamp ends have a small gap even when the derailleur is firm and secure, as you can see in the 1st photo. Closing the gap breaks the hinge part.
The 2nd photo shows the nature of break and the repair I did on the one on my wife's Bianchi. Not the most elegant but completely effective:
[IMG]
IMG_1337 by
r80ksbits, on Flickr[/IMG]
[IMG]
IMG_1032 by
r80ksbits, on Flickr[/IMG]
On all my builds, I never try to close the small gaps at the ends of FD bands exactly because of this.
Worst I did was bend the hinge pin at the band hinge, which told me I went past the acceptable point of tightening the hand clamp and had to back it off.....
I suspect that most FD band clamps are actually .25 to .5mm ID smaller than standard seat tube diameters when closed with no gaps at their ends, to assure enough clamping force around the seat tube....