I have a question concerning compatibility between Shimano 9 and 10 speed systems please:
Old Bike: Dura-Ace 9spd downtube shifters, Ultegra 9spd hubs, Ultegra 9spd cassette, Ultegra 9spd chain, (Old!) Shimano 600 r/d - works beautifully as a 9spd.
New Bike: Dura Ace 10spd STI shifters, Dura Ace 10spd cassette, Dura Ace 10spd chain, Bontrager wheels
I have also bought a 105 10spd cassette that I have fitted to the wheels from the old bike so that I can use my old Ultegra hubbed wheels on the new bike for training and keep the new Bontragers nice. However, I want to keep using the old wheels with my old bike on my turbo trainer.
Question: What will happen if I use the new 105 10spd cassette with the 9spd Ultegra drivetrain on my old bike? Will anything break or wear? Will I just suffer dodgy indexing, which I'm not bothered about as I'm quite happy to use friction shift on the turbo trainer. Or do I have to change back to the 9spd cassette every time I want to use the wheels with the old bike?