Hello, I am out of ideas, under load/standing on pedals while in big ring and either 21 or 23(11-23 cassette), the rear creaks driving me nuts. I have inspected my fulcrum racing 1 wheel set, that's all good. Did any one else had this problem, I can't find where it's coming from, sounds like its the rear Hugh, please advice. Thx

if its only in the 21 and 23, it's either that your cassette lockring is not tight enough, or (most likely) the rivets holding those cogs to their aluminum spider are creaking. if it's the rivets, i'd clean them very well with a degreaser like Clean Streak, blow dry them, then apply a wicking loctite to the rivet/spider joints. wicking loctites are generally for threads and not cylinder retaining, but it's worked on 2piece centerlock rotors for me so i feel itll work on a cassette.

Also try cleaning and regreasing freehub pawls. This can be a source. A.

egreasing freehub pawls was the first thing I did, thanks

It does not often get mentioned, but cassettes can make creaky noises. Remove, clean off all the mating surfaces, reassemble with a light rub of oil, tighten properly, and see if that cures it.

Skewers are another source, and in the lowest gear are seeing the highest torque.

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dangerous curves ahead

Kind of on a limb.. creaks often sound like they are coming from other places that aren't and only happen at certain times.. did you regrease your BB cups ? I had a nasty creak on my aluminum Prince SL... tried everything then tried the BB cups and problem solved..

Also ghost noises..on my Cannondale I had a banging noise.. thought it was valve stems... turned out it was the seatpost.. installed some carbon compound and it shut up...