With regards to how many sprockets on the cassette, all you need to worry about is that the number matches the shifters. A 9speed shifter will pull slightly more cable than a 10speed shifter. You can pretty much use any derailleur with any cassette as far as I am aware.
So no, a new 10sp cassette won't be compatible with your 9sp shifters.
With regards to how many sprockets on the cassette, all you need to worry about is that the number matches the shifters. A 9speed shifter will pull slightly more cable than a 10speed shifter. You can pretty much use any derailleur with any cassette as far as I am aware.
So no, a new 10sp cassette won't be compatible with your 9sp shifters.