Drivetrain smoothness troubleshoot

[nemeseri]

I just sit on my other bike (trek emonda factory BB90 BB) that has a recently replaced bottom bracket, but older chain / cassette and noticed that the drivetrain runs much smoother and is quieter than my caad10's (rotor bb30 / 24mm converter BB with shimano cranks).

What are the main things you would check? The caad10's BB runs ok, the chain and cassette are clean, no movement in the crankset. What I noticed that if I turn the pedals backwards, there are gears that are more noisy and the rear derailleur (or chain/cog) clicks. Although I have no issues with shifting nor turning the cranks in the right direction.

Maybe I just need a rear derailleur tune up?

[sungod]

check the hanger alignment, it can make things noisy, then index the rear mech

bear in mind that different frames/wheels can sound different depending on resonances, high frequency damping etc.

[nemeseri]

check the hanger alignment, it can make things noisy, then index the rear mech

bear in mind that different frames/wheels can sound different depending on resonances, high frequency damping etc.

Thanks! Today I checked the bike in the stand and adjusted the indexing and stops. It's much better now. Although I noticed a weird thing: in big-big if I turn the chain backwards it jumps off the largest cog to the third (!) largest. Why is that? The stop seems to be ok, indexing works and if I just turn the crank clockwise it seems to be ok.

Also I noticed some grinding sound if I'm in big ring and small cog. I checked the b tension screw and there is definitely room between the pulley and the cog.

Any tips are welcomed!

[kkibbler]

You adjusted indexing and stops (I assume you mean limit screws). Did you check hanger alignment?

Some chainring-chain-cassette combinations are inherently noisier than others, but unintended shifting in any direction is an actual problem.

[racingcondor]

Worth checking chain length as well. My guess would be either the hanger or a chain that's too short.

[helldiver]

Also check the condition of your derailleur pulleys. Many of them are rotating on plain bushings, if those get really dirty, the pulleys won't spin freely at all. I noticed a big improvement in the smoothness of my drivetrain when i disassembled and throughly cleaned my ~2 years old pulleys in Campagnolo Athena 2013 derailleur, i later changed them for Tacx pulleys running on ball bearings, because i think that sealed ball bearings will remain freely spinning without cleaning for much, much longer.