I get a grinding noise coming from the vicinity of my 7700 (9sp DA) rear hub during the highest-torque portion of my pedal down-stroke at the end of long climbs and only in the largest 2-3 cogs (27, 24, or 21). This seems to happen only when the temperature dips to <55F (at elevation) and is cured when I start going downhill, which also puts me in warmer temperature. The noise seems in synch with the chain speed and is not caused by any observable rubbing or rear derailleur miss-adjustment. There are no abnormal noises when freewheeling, the hub seems well-adjusted, and there is no pawl slippage that I can detect.
At one point I had the theory that the removable derailleur hanger/dropout on my Cannondale was perhaps shifting because of climbing torque and giving a slight angle to the rear wheel--braking for the descent would then slip it back! So I tightened it and the noise went away...alas my self-congratulations were premature as the timing also coincided with the weather changing. I got the noise again this Sunday during an uncharacteristic cold snap, so there goes my last theory.
I get a grinding noise coming from the vicinity of my 7700 (9sp DA) rear hub during the highest-torque portion of my pedal down-stroke at the end of long climbs and only in the largest 2-3 cogs (27, 24, or 21). This seems to happen only when the temperature dips to <55F (at elevation) and is cured when I start going downhill, which also puts me in warmer temperature. The noise seems in synch with the chain speed and is not caused by any observable rubbing or rear derailleur miss-adjustment. There are no abnormal noises when freewheeling, the hub seems well-adjusted, and there is no pawl slippage that I can detect.
At one point I had the theory that the removable derailleur hanger/dropout on my Cannondale was perhaps shifting because of climbing torque and giving a slight angle to the rear wheel--braking for the descent would then slip it back! So I tightened it and the noise went away...alas my self-congratulations were premature as the timing also coincided with the weather changing. I got the noise again this Sunday during an uncharacteristic cold snap, so there goes my last theory.
Any suggestions?
Cheers, Shawn
Can you find some locals that are willing to do some temporary parts swapping? I would try swapping the rear wheel first to help eliminate it as the source... and because it is easily done. I would also check the chain and cogs for wear. I would clean the rear derailer, making sure that you put the jockey wheels back into their proper positions. Check over the derailer for anything that looks suspicious like sloppy lose pivots or pivots that don't pivot freely. Check for run-out and wobble in your hub and freehub. Check for lose cogs on your casette.
