Bicycle Mechanics - Unsmooth Pedal Stroke - Specialized Roubaix 09
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I recently picked up a Specialized Roubaix and due to weather have only been using it on a trainer. I initially didn't think much of it, but when I make a pedal stroke it feels 'bumpy'. Its a new bike, and has full Shimano 105 components.
Its kind of hard to describe, but almost as if every tooth on the crank or cassette is making small bump feelings when the chain seats itself on the crank or cassette. I can only notice it when I am putting a bit of torque on the pedals instead of just lightly spinning. I really have no idea what it is, and am hoping I don't have to take it back to my LBS to get them to look at it if it something simple.
I did a few checks, and it isn't any sort of rubbing on the front deraileur, and the rear looks fine. However I'm unsure what else it could be.
01-16-10, 02:23 PM
checked for play in cranks/bb/pedals?
A slightly loose pedal will cause this, and will be a big problem later, as will a slightly loose crankarm...
also check tightness of crankbolts.
I did a bit more playing to see where I can isolate the sounds. It seems to be coming primarily from the Rear Derailleur, I might just bring it in for them to look at as its barely been ridden at all since I bought it.
01-16-10, 03:22 PM
Its a stretch but perhaps the B-tension screw is not adjusted properly and the upper pulley is rubbing on the cassette. If its a new bike take it back to the shop and have them check it out.
01-16-10, 03:31 PM
It sounds like a cable adjustment for the rear derailleur is needed. If the indexing isn't adjusted correctly, the chain will want to skip to the adjacent cog (bigger or smaller depending on direction of the error) but can't quite make it and the skipping is what you are noticing.
Stiff chain link?
If it were stiff chain links it would have to be all of them. As its not a periodic bumpyness, but consistant with each motion. Has to be a few dozen small bumps with each rotation.
01-17-10, 12:50 PM
Another option is tyre seating -
Have you checked the chain for stretch? A stretched chain does not mesh well with the chainring teeth or cog teeth.
On a trainer the dynamics of the bike are not quite the same because the rear wheel is locked in place and the side to side sway caused by alternating forces on the pedals distorts the frame and drivetrain alignment more than if you were riding on the open road.
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