Ultegra FD-6700 Does Not Fit Around my Seat Tube
 

I have a 2008 Cannondale Six 13 frame which has a 34.9 seat post tube diameter. I have an Ultegra FD-6700 which is a clamp on, stamped right on it, 34.9 as well and for the life of me cannot get it to close around the tube. The screw is a little too far away to thread in. It may work with a longer screw but I'm thinking something is not right. There is no spacer on there either.

Any ideas or recommendations?

A picture would help.

http://bikeforums.net/attachment.php...hmentid=199122
http://bikeforums.net/attachment.php...hmentid=199123
http://bikeforums.net/attachment.php...hmentid=199124

Thanks for the photo.

As pictured, there is a considerable gap in between the seat tube and the clamp. IF your frame requires 34.9 and you actually have a 34.9, should fit if you close it all the way. A lot of the time, the fit is tight enough that the clamp has to flex a little, to where it sort of pops on. How tight are you squeezing the clamp? If you have squeezed it more than moderately tight and it hasn't popped on, then it's the wrong size. If you read correctly on the inside of the clamp that is says 34.9, it may have been mislabeled.

P.S. It's entirely possible that it was mislabeled from the factory. I have a "120mm" 3T Arx Team stem I bought new that is actually 130mm. In any case it's probably a 31.8. To verify this, try mounting it on the seat tube of your CAD 2, if it fits flush, it's 31.8.

It does fit flush. Damn you Shimano!!!

In my experience, the measurement is cast into the inside surface of the derailleur clamp. I'd trust that before I'd trust any printed labels.

If it was the wrong size clamp then it would be way off. Based on the photos, it has to be the correct nominal size because it is very close. I've had some frames that had an excessive amount of paint, making the tube diameter a bit more than the required 34.9mm. Clamping the FD threrefore resulted in marring the paint. Try using a longer bolt to clamp it down, and it will probably then close up enough that you can take the long bolt out and replace it with the stock, shorter bolt. If you get the FD position (height) correct first time then the damaged paint should be (mostly) hidden by the clamp, but that is not always possible. Good luck!

clamp on a cannondale? No braze on holes? I don't think clamping anything to aluminum (or carb) is a good idea-esp with the stress a fd has. Are the newer ones made this way? Learn something new every day.

OIC-very low torque. Still scary.

Cannondale went to a clamp on FD for their aluminum bikes around '93, same time as they went to a seat tube clamp instead of a through-bolt. Might have gone back and forth on both (or either) over the years, but they have not used braze on FD's for every model. Even the old ST touring bikes used clamp on FD's back to '83.

I had a similar problem on my 09 Madone 4.7 (though not as bad as that one). The Madone has lots of paint on it. I replaced the bolt with one that was 5mm longer. Once the threads caught, the clamp closed up fine (still about 1/4" gap between the halves -- but flush fit all the way around).

I put the another 34.9mm Ultegra 6700 FD on another bike that I built (unpainted carbon frame) and was able to use the original bolt, but it still couldn't be turned in very far. IMO, the clamp hole is a touch undersized but paint on the seat tube makes the tube itself a touch larger than 34.9.

Bob