gbot

Got a frame replacement last year on warranty. Had the new bike built up and instantly noticed a problem with vibration coming through the pedals (mostly on the drive side) when seated putting down big power. Can never detect it while standing, but that may be due to the fact that it only really comes through when I'm 'pedaling circles'. Most noticeable when the drive side pedal is between 9 and 12 o'clock in the pedal stroke. Only new part on the bike was the chain. It's sort of a muted vibration but is definitely noticeable.

Originally it was just in the small cog but seems to be getting worse (i.e. moving up to larger cogs. NEVER happens in the small ring. I've gone through a list of what I thought the problem was and my steps to eliminate those possibilities:

1 - BB adapter - press-fit adapter was replaced with FSA sleeve
2 - Cassette - bought new cassette
3 - Chainring - bought new chainring (as well as another new chain)
4 - BB - took off crank, checked BB, no problems, in great condition
5 - Derailleur hanger - checked der hanger, was *slightly* out of true, replaced with a new one
6 - Pedals - tightened pedals, then swapped out with other pedals
7 - Wheels - tried other wheels, tried original wheels on backup bike

None of these have identified or solved the problem.

I believe I'm left with the following possibilities:

- slightly bent crankarm (Ultegra SL, can't detect anything wrong with it with the naked eye)
- RD problem (shifts beautifully, pulley wheels maybe?)
- Frame (can't see how it would be the frame but the list is getting a bit short so I have to consider it)

The key wrinkle here is that all of the components were on my old frame, and the problem never happened on the old frame. It started INSTANTLY at day 1 on the new frame. This was after a bit of a nightmare getting the shop to build up the bike - not my regular shop and I have very little faith in the wrenches at this particular place. So if it is something like a bent crankarm caused by improper handling of the crank/bike, that wouldn't surprise me. But again, no marks that I can see on the crank and it seems straight from looking at it.

Currently my next steps are to have it into the shop again for the umpteenth time and get them to take a really close look at the RD, specifically the pulley wheels. If that looks fine I am going to try to find a spare crankset somewhere to put on.

If anyone could chime in with opinions I'd appreciate it. The bike is a 2010 Tarmac Pro SL. DA 7800 RD, Ultegra SL crank + pedals.

ADSR

Perhaps it has something to do with chain tension and how it's mating up with the chain rings/cassette. Something causing a slack(er) chain to vibrate?

merlinextraligh

Is the chain on the right direction. Some chains do not play well with the 11 tooth if they're on backward. Given that your problem happens only in that one cog, I'd check that.

gbot

The chain's on the right way. Also, it doesn't just happen in the smallest cog, but is worst there. This points to a chain problem I guess, because it's moving across the cogs fastest when it's in the 11.

Since I replaced the chain and chainring it is slightly different. Still there but not as 'loud' and actually more noticeable on the lower cogs.

Someone on a different forum suggested it might be the Shimano chain, and that it's just 'something that happens' with Shimano chains. He described it as a cell phone vibrating in your shoe, which is exactly what it feels like.

Problem is I've already got close to 500km on this new chain and had much more on the previous one and the problem didn't seem to go away.

snowman40

I had something similar, I went an adjusted my rear derailleur to where I had one gear...I had to take it in to a shop to get it fixed. My derailleur has a B screw, adjusting that fixed my vibration problem.

scirocco

I've had the same vibration problem, and never really got to the bottom of what casued it. However, it was improved a bit by using a heavy wet lube.

tanguy frame

chain angle/alignment?