I just bought a new carbon frame and with all the dire warnings on the internet about crushing the fiber, I'm being a little paranoid. I picked up a carbon derailleur clamp in 34.9, and it's too small. At least, there's an 1/8"+ gap when I try to close the clamp. Does my frame need a custom size clamp or is this okay? (Yes, I measured the clamp and its 34.9mm). I tried an aluminum clamp and its the same.

The frame has a dimple/indentation around 4" up from the bottom bracket - is that just to provide clearance to the chain or FD?

The der's height above the shell is determined by the large ring clearance, where the frame dimple then lines up will suggest what it's for. I do suspect the dimple is for parallelogram clearances. Have you tried the carbon der clamp on a steel or metal tube yet to see how it fits something else? It's pretty common for clamps to seem a tad small/tight at first. Too bad that clamp uses one bolt to do two things. Andy

Parlee?

I own two of those clamps.

The one in the photo above isn't right. The clamp is too small or the tube is too large. Tightening the bolt is going to deform the thin concave portion of the clamp in contact with the front derailleur. It likely won't hold the derailleur properly resulting in poor shifting performance.

My experience is that carbon frame tube diameters are less precise compared to alloy or steel. The photo below is how it looked when tried on a Niner RLT 9 RDO carbon frame. It could not be used this way and a Dura Ace clamp was reluctantly used.

The same clamp works perfectly on an alloy bike which has a layer of powder coat on it.





-Tim-

Omni Racer. It measured right. The tube is just big. A metal clamp is also too small. I had the same issue with an aluminum frame, same manufacturer. That one also has the dimple. The derailleur is Campy.

I just measured. It's right on, from front to back, but from side to side is 35.6mm

Time for some patient file work, or a Dremel-type tool with a sanding drum. For the clamp of course.

Not with the CF clamp, but maybe with the aluminum one. I may just try forming it a little to better conform to the shape of the tube. I really didn't want to use an aluminum clamp.

Digging around in my cycling closet, I found a Campy clamp. No better than the others but I suppose it's the best I'll do.

I may try 3D printing a spacer and see how the carbon one does with some support.

K edge is another maker of CNC US made clamp on FD mounts..

+ an overshift chain catcher to go on the same bolt..

Call the mfr. of the frame. They may make, or recommend, a specific mount for yours.

I reached out to Pinarello, and to the shop I bought the frame from. I'll share if I hear anything.