10 speed chain skipping on 9 speed cassette I have recently replaced a 9 speed chain with a 10 speed one on a 9 speed cassette. I read this is compatible. Shifting is fine and quieter but it is now jumping on the smaller cogs 6-9. Is this a common occurrence? Never had any skipping on 9 speed chain though it was a lot noisier.
This feels like a new chain on a worn cassette problem.  The fix is to replace the cassette, and soon before your chain suffers accelerated wear.
Assuming you have 9 speed shifter and rear mech still, the slightly narrower chain won't really make any difference while pedalling, and shifts might be slightly sloppier.
I run a 10 speed chain on a 9 speed cassette without issue, because its what I had at the time.