Are 9 speed and 10 speed cassettes interchangeable?
I am going to purchase an Open Pro wheel with a PowerTap 2.4SL. I have two bikes that I want to use it on. The first bike is a Cervelo P2C and I count 9 rows of teeth so assume this is a nine speed. The other bike is a Motorbecane LeChamp. I count 10 rows of teeth so assume ten speed.
Is it possible to buy a 9 or 10 speed cassette and use it on both bikes? Or if I want to use the PowerTap on both bikes am I going to have to buy two cassettes?
The P2C is a Shimano Ultegra 12-25 and the Motobecane is Ultegra 6600 11-23T.
Also if I buy a Shimano CS-6500 9 speed from PerformanceBike would this be compatible with 9 speed Ultegra 12-25 on the P2C?
Thanks in advance for any help. I am confused how this works.