Originally Posted by
Kapusta
An 8 speed chain on a 9 speed cassette is not going to work very well. It is too wide.
8 speed crank with an 9 speed cassette needs a 9 speed chain.
4.8 mm vs 4.34 mm center-to-center
I'm afraid you're right.
https://sheldonbrown.com/cribsheet-spacing.html
The outer chain plates will probably rub against the larger sprocket. I'll try it and see, then report back here in case someone else does a search on this subject.