Wheel out of balance; cog rocking

[virasana]

Hello,

I had a recent incident with a pavement, during which my back wheel crashed into the pavement at medium speed, leaving me with a flat tube. I replaced the tube, but was left with the above problem i,e, the wheel is out of balance, and the cog 'rocks' when spinning. The cog is solidly fixed onto the hub, but it is eccentric when the wheel spins. It feels like the hub-internals are damaged. I subsequently replaced the tyre with a new one, but left the recently replaced tube. I have checked the rim, and it seems to be almost true, so this is not the problem.

Any ideas on what the problem might be, and how to go about repairing it?

btw, this is a folding bicycle with 20" tyres.

[xerxes]

It sounds as though the wheel axle might be bent, I can't think how an impact with the curb could effect the freewheel/cassette directly.

Try dropping the wheel out, you should be able to see if the axle is bent.

[virasana]

(07-29-2010, 01:50 PM)xerxes Wrote:  It sounds as though the wheel axle might be bent, I can't think how an impact with the curb could effect the freewheel/cassette directly.

Try dropping the wheel out, you should be able to see if the axle is bent.

OK, thank you. I take it one can replace the wheel axle easily.

[xerxes]

It's not impossible, but a bit of a fiddle. If you replace the axle, you should probably replace the ball bearings and the cones at the same time. However, check that the existing axle is actually bent first and that this is the problem. If it is, disassemble the hub and also check that the bearing faces in the hub itself haven't also been damaged before buying new parts.

If the hubs bearings faces have been damages, you'll have to replace the whole hub and have it rebuilt into your existing rim, or replace the whole wheel.

If you only need to replace the the axle, cones and ball bearings, you will need some cone spanners to reassemble and adjust the bearings.