I have a cannondale supersix and here is my issue. I cut my 3t Doric down and left about 10cm that goes into the down tube more than the min line. My issue is when I pedal on the flats say about 25 to 30mph I get a very annoying tick sound. This started after I cut my seatpost not sure if that is the problem. When I climb no tick in or out of the saddle just seems to be at a fast cadence not sure if it is the saddle or something else. I would appreciate any solutions to this issue. Or anything to try to narrow it down. I already tried difference skewers no change.

Seat rail clamps are frequent offenders for me.

What's the solution should I try carbon paste on the seatpost?

I take all the pieces apart from the clamp, clean them and apply carbon paste to the rails and the interface between the rail support and the post. That interface wants to slip with your weight is leveraged off back end, causing squeak. Higher torque may be all is required. I do the paste to just be done with it.

if the post is able to rock slightly in the frame, it will tick. make sure you have sufficient torque. also, grease clamp bolt and the inside of the clamp, and grip paste the post.

My woodman seat clamp says 5NM max does that sound like enough torque?

yup

Funny.. I have a 2010 Supersix HiMod and had the EXACT issue.. have an FSA K Force post (uncut) but I would get this huge banging sound.. it sounded like a valve stem banging against the rim bed.. I went nuts trying to isolate it...I beleive someone on here gave me the solution.. get some FSA compound paste, rub it onthe post where you insert it... put a small amount on yor seatpost bolt, and clamp it down to spec.... ticking gone instantly.... it happened again earlier this season, I just reapplied some paste.... Funny we both have the same frame and same issue.. I never had that with my former Pinarello carbon frames...

Get some clear coat and put it on the post and parts that need to be clamped . You can build it up so that you have a nice tight fit . Then use carbon paste and you will not have to tighten so much and seatpost will be more secure as well .

i have used some stuff called Monster Grip for my paddle boards and surf boards. It's a spray that's almost like a clearcoat but has a texture that is really rough when it cures. Might be a more stable alternative to carbon paste.

find someone to switch seatpost/saddle with so you can help diagnose the problem.

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Thanks for all your input carbon paste has done the trick.