Do you put anything under the clamp on the carbon to protect it? In the past I've tightened brakes on MTB handle bars to much and wrecked them so I'm wondering.
I've mounted lights on carbon forks and the thought of over-tightening the clamps made me wince every time... (I put a strip of old tube underneath, but no idea if that's the best thing to do)– darkcanuckSep 23, 2010 at 4:19
Carbon seatposts are also another part to be careful with.– Dana the SaneSep 23, 2010 at 13:10
1My understanding is that parts have to be the right size for carbon, and fit to the correct torque (so you need a torque wrench) and carbon assembly paste. You don't use shims or straps or any tape between components and bars/frames because that means you have the wrong size.– Criggie ♦Feb 25, 2018 at 4:42
Carbon compound can definitely help. As the following link points out, it helps you avoid 'over torquing' to ensure that the component doesn't slip.
In my personal domain, if there is carbon and carbon, or carbon and some other material, thou must use fiber grip. And a torque wrench. No questions.
There's no need to treat the underlying carbon before installing a clamp-on front derailer. Fiber Grip or a similar assembly compound helps increase grip under lower torque, but this does nothing to prevent you from over-tightening the bolt and crimping the tube. A torque key and patience are required for that.
I recommend picking up a pre-set torque wrench like this:
Example is from https://www.amazon.com/Ritchey-5Nm-Multi-Torque-Key/dp/B009F93S9C but many bike shops have similar tools.
It's small enough to fit in a saddle bag and I bring it with me on rides in case anything slips and needs re-tightening.
1Concur - so much stuff on a modern bike is ~5 Nm its a valuable tool to have. The "well-calibrated elbow" is sometimes not good enough.– Criggie ♦Feb 26, 2018 at 6:04
2Excellent first answer too - I've edited it a little to bring an image in-line, because they're stored on imgur servers. That way if the linked product goes away, future readers will be able to see what you meant, and find a suitable replacement.– Criggie ♦Feb 26, 2018 at 6:07