Bicycle Mechanics - 8 speed cassette with a 9 speed chain?

It seems to me that it should work, but I was interested in what folks had to say about it.

My "A" bike has a 9-speed Ultegra drivetrain, my "B" bike has a 8-speed RSX drivetrain. They both have triples on the front. I want to bring the "B" wheels as backups for a race on Saturday.

I guess I could try to pick up a used 9-speed cassette, but wondered if I could just slap them on the bike in a pinch.

What do you think?

It seems to me that it should work, but I was interested in what folks had to say about it.

My "A" bike has a 9-speed Ultegra drivetrain, my "B" bike has a 8-speed RSX drivetrain. They both have triples on the front. I want to bring the "B" wheels as backups for a race on Saturday.

I guess I could try to pick up a used 9-speed cassette, but wondered if I could just slap them on the bike in a pinch.

What do you think?Your problem will be the 9 speed shifters trying to shift a 8 speed cassette.You could have additional problems with the fact that if you have different hubs or even same make hubs may require derailer adjustment when you switch wheels.The chain width is not really an issue, but when you switch cassettes with the same chain,differences in cassette wear can have a mal effect on the chain.

A new cassette will only cost you about $30. As far as the chain goes, a 9 speed chain MAY work, but the cogs on a 9 speed system are thinner, and so is the chain.

I'm not really concerned with the chain or cassette wear, as tommy2pants points out, because it's just an emergency back up that'll only be used for 20 miles maximum. But the shifting problem would be a killer.

I think I might swing by the LBS and see if I can pick up a 9speed cassette cheaply. I really ought to have a set of training wheels anyway.

Thanks for the replies, guys.

As far as the chain goes, a 9 speed chain MAY work, but the cogs on a 9 speed system are thinner, and so is the chain. Even a 10 speed chain works just dandy on 8 speed cogs.The cogs ae really only wider enough to matter BELOW where the chain sits. Same for chainrings.

[edited]

I guess I was concerned about the chain jamming.

As far as I can remember, the RSX hub is not a 8/9 speed hub. I don't think it will accept a 9-speed cassette.

For the future, you can pick up a pretty nice rear wheel and a spare cassette for around $100 off the web. Check it out.

Marc

As far as I can remember, the RSX hub is not a 8/9 speed hub. I don't think it will accept a 9-speed cassette.
RSX was made as both 7 and 8 speed. The 8 speed hub is also 9 compatible.He started out saying he had an 8 speed drivetrain.

Yup. 8 speeds. As it turned out, I never made it to the LBS and put my faith in a glass-free course. Everything turned out fine and I'll post my race report in the Road Racing section.