Bicycle Mechanics - Strange Drivetrain noise/ behavior

Bikeforums.net is a forum about nothing but bikes. Our community can help you find information about hard-to-find and localized information like bicycle tours, specialties like where in your area to have your recumbent bike serviced, or what are the best bicycle tires and seats for the activities you use your bike for.



PDA
YungBurke
02-21-09, 12:44 PM
Hey guys I have a puzzler. My drivetrain has been behaving very strangely. Whenever I put any kind of power down, there is this strange grinding noise which comes from the casette area. Also, periodically the chain will feel like it slips for about 1/4 of a chainring revolution. I replaced the chain, oiled, and adjusted the rear derailleur and the slipping is less prounouced, but the grinding and some slip is still present. It occurs on every chain ring and there doesnt look like any "shark fin" action on any of the rings. One thing I have noticed is the derailleur seems to not rotate as freely and will sometimes seem to get caught and rise up towards the chainstay slightly. It also isnt as effective at holding the chain on the right cog when backpedalling. The cage looks like it may be bent, and I am investigating a replacement now, but does this seem consistent with the symptoms?

DaJMasta
02-21-09, 01:41 PM
Could it be a problem with the ratchet mechanism in the freehub?
YungBurke
02-21-09, 02:09 PM
Could it be a problem with the ratchet mechanism in the freehub?

This is definitely a possibility. I may have bent the axle at some point or another, there is a very slight "wobble" in the cassette if you freewheel quickly. The only thing is this phenomenon has existed for a while without the above issue, and the wobble may just be an illusion of the shift ramp pattern since its only perceptable at high rpm.

HillRider
02-21-09, 02:48 PM
A new chain on a used cassette will frequently cause skipping.

Also, check the new chain for a tight link. Pedal backwards slowly and watch the chain as it exits the lower rd pulley. A tight link will cause a kink in the chain at that point that is obvious.
Panthers007
02-21-09, 02:50 PM
I'd overhaul the freehub. Sounds like it might need new pawls, or something.

Good luck.
YungBurke
02-21-09, 05:44 PM
A new chain on a used cassette will frequently cause skipping.

Also, check the new chain for a tight link. Pedal backwards slowly and watch the chain as it exits the lower rd pulley. A tight link will cause a kink in the chain at that point that is obvious.

Yeah, im familiar with this this, but the problem got a bit better with a new chain. Also, no tight links on the chain, and the skipping only occurs under moderately heavy pedaling/ accelerating.