Question & Answer Archive

Equipment - Transmission - Rear

I understand that, if one has a broken spoke on the rear wheel, block side, there is a tool that can undo the block 'on the road'? At the moment I use a block remover,24mmSpanner and chain wrench.

The device you have seen is made by a company called Pamir, and is a Casette Cracker. The problem is that they are suitable for use only with Cassette hobs where the top sprocket of the cluster screws on, and secures all the others onto a freewheel unit that is integral with the hub. This applies to early Campag cassette systems (7 spd. only) and some Shimano cassette systems.

If you have a screw on type freewheel, where the whole freewheel screws off the hub, ie, a pre-cassette type system, I don't know of a lighter alternative to the kit that you already carry. The only odd possibility in this case is that you are using large flange hubs, in which case, you could conceivably use a cassette cracker to strip the sprockets off the freewheel body, and then relace the spoke, as the hub flange on LF hubs is wider than the base of the freewheel body.

If you have a Shimano cassette, and the top sprocket is secured by a locking ring, not the top sprocket itself, pamir also make a tool called a Hyper Cracker which works essentially the same way as a Cassette Cracker, but allows the removal of lockring and therefore cassett, to gain access to the hub flange. If you have a Campag cassette of this design, you have a problem, as the Campag locking ring has a different spline size and interval to Shimano, and the tool won't fit. As far as I am aware, Pamir never made a version of the Hyper Cracker for Campag.

What is the difference between a cassette and a freewheel?
A Cassette is a set of sprockets that fit onto a hub which has the freewheel mechanism built into the body of the hub itself. A freewheel screws onto a hub, and carries the sprockets on the freewheel mechanism, and is separate to the hub itself. Most modern hubs are of the cassette type, as there are a number of mechanical advantages over a separate screw-on freewheel arrangement.
What is a fixed wheel?
A fixed wheel is an arrangement whereby a single sprocket is screwed directly to a specially designed rear hub, and retained in place by a locking ring, usually screwed on anti-clockwise. There is no freewheel mechanism, so that if the pedals stop turning, the rear wheel will stop turning. This arrangement is the only permissible arrangement for track bikes, and is also often used by commuters and cycle couriers because it is an almost zero maintenance set up.