I recently acquired an older mtn bike with a very light aluminum frame that has 8spd XTR shifters and derailleurs in good condition but with a trashed STX crankset and BB. I'm wondering if an '09 9spd XT crankset would work smoothly with an 8speed cassette and if so, what would be the best chain to use.
I figured I'd need a new cassette. The question is which one? I read the compatibility info by Sheldon Brown, but it didn't quite clear it up for me. Can I use a 9-speed cassette with an 8 speed derailleur (and shifters)? If so, this would be ideal as I plan to upgrade to 9-speed shifters and different brakes down the road.
Well... Sheldon writes about "8 of 9", where you use 8sp shifters with 8 gears of a 9 sp cassette. I think this is not only difficult to set up correctly but also prone to automatic misadjustments, as the cable stretches, the RD gets knocked at etc. So I would not do this. If you want to upgrade, this is the time. Or next time, when you change chain and cassette. So if you don't want to invest the money in the new shifters at the moment, go for an 8sp cassette / chain and drive them some 1000 km. I think, the 30 (or so) that you spend now on an 8sp drivetrain is money well spent, if that means you have less problems in the near future.
Thanks, Joe. I appreciate your input.