Rear cassette question

[atomistabby]

Hi all,

I am hoping to put together a rear wheel to be used solely on my indoor bike trainer with the trainer tire (to avoid changing out the tire).

I bought a used rear wheel and installed a 10 speed shimano 12-25 cassette on it that I had laying around. However, it doesn't work. The chain falls off the biggest rear gear (smallest one, outside of the bike).

My regular wheel used a 10 speed shimano 12-28 cassette.

Will I need to find a 12-28 cassette to make this work? Or should the 12-25 cassette be working?

I want to be able to interchange the two wheels so I don't want to have to do other adjustments to make any of the two wheels work.

Many thanks

[Joe_W]

Without seeing the bike: it sounds more like an alignment problem. The cassettes on different hubs sit in slightly different spots. Depending on the hub you might be able to mess around with spacers to move the centre of the hub over to one side.
Easiest thing would be to get two identical rear wheels...