I have a TT bike with 9 speed shimano cassette and friction shifters. Can I pull the 9 speed cassette and put a 10 speed on (it already has a 10 speed chain)? Will the wheel dish/hub spacing be correct? Any other changes/adjustments neccessary? The wheel is a Mavic Aksium if that is of any consequence.
I've done this with STI and it works fine - friction should be even easier. You should have a thin spacer that came with the 10sp cassette for use with a 9sp freehub. I had to adjust my rear derailleur limits to obviously omit one gear, but you will likely be able to hit all 10.