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I need help with a curious knock.(6 posts)

I need help with a curious knock.Mel Erickson
Mar 19, 2003 8:05 AM
My recently built one speed has a knock which I think is coming from the bottom bracket. This is an old Panasonic frame and the cups are original but the axle and bearings are new. The knock is rythmic and seems to get louder when I put more pressure on the pedals (like when standing and cranking up a hill). The knock comes and goes, although lately it is knocking most of the time. Adjustment is good, no play but not tight. Bad bearing (they're in races)? Should I repack with loose balls? Could the axle have a burr (I checked it pretty carefully before installing)? Cups damaged? Not the BB at all but the rear hub (no knock when coasting)? The chain is old but in good shape (no stretch and no tight links). The chainring has one or two damaged teeth but this shouldn't cause a knock, should it? The freewheel is new and is BMX. Any thoughts?
had same problem on steamrollerJS Haiku Shop
Mar 19, 2003 8:07 AM
removed bb (sealed), cleaned shell, greased all (incl threads), reinstalled w/new chain, tightened all chainring bolts, etc.--most had to be done for routine maintenance, anyhow. no more knock.

HTH.

-J
Had the same knock, cleaned and adjusted the chain. (nm)onespeed
Mar 19, 2003 8:14 AM
check the bb cups and axle.jw25
Mar 19, 2003 8:18 AM
That definitely sounds like a worn race to me. Pull the bb cups out, and check for pitting or excessive wear. If they look good, try fitting new bearings and readjusting. The bb needs to turn smoothly with no play when the lockring is tightened down. This is also a good opportunity to clean out the BB shell threads and cup threads, and regrease. Grit might also cause a tic, but I'd bet it's the races.
Or you could pick up a UN-52 or UN-72 replacement for $15-$20, but they aren't quite as smooth.
had the exact same problem on a bike oncegreg n
Mar 19, 2003 10:49 AM
Same thing as you describe. A knocking that sounded like it was coming from the bottom bracket. And I wouldn't hear it when I was coasting. I ended up changing the bottom bracket, but the noise persisted. Then I switched to a different pedal system. Noise was gone. Turns out one of the old pedals had just enough play between the spindle and the body to make the noise. So check your pedals. It only takes a little play.
Good thought and easy way to checkMel Erickson
Mar 19, 2003 12:06 PM
I have another pair of pedals and can switch them in minutes. This should determine if the pedals are the problem. Much easier than tearing apart the BB. I'll try this first. The pedals are off an old mountain bike and did receive alot of abuse. Maybe it's their time.