What is the difference between 9sp and 10/11sp cranks/chainrings?

Question

I have a 9sp setup I’m very committed to, mostly because I can’t find 10/11sp indexed downtube shifters (Dia Compe makes a non-indexed 11sp and that seems to be it). I want a new crank with swappable chainrings to support a 2x9 touring setup and a 1x9 city setup.

I assume the 10/11sp chainrings have different tooth thicknesses than 9sp chainrings. Please confirm that. I’ve also seen the cranks themselves specified as 10/11sp and I’m wondering if maybe the chainring positions are spaced differently than they would be on a 9sp crank. This is my main concern as it’s hard to find cranks specified for 9sp.

Answer 1

8, 9, 10 and 11 speed chains are progressively narrower to accommodate the necessary closer spacing of sprockets in the cassette. The distance between the inner plates is the same, but the width of the outer plates and rivets is different.

The main difference between crank sets designed for 8, 9, 10 and 11 speed chains is the chainring spacing as you have guessed.