I bought a used crankset from my local bike collective. It has a single 44-tooth chainring and I intend to use it for a single speed conversion with a new cog and chain, but I need to figure out what dimensions of those latter components to buy.

Most advice I see online says that single speed and internal gear hubs use 1/8" chain, while derailleur bikes use 3/32" chain. Great! Doesn't help me here: I don't know what kind of bike this crankset came from. It's only got one chainring, but that doesn't mean it couldn't have come from a bike with a rear derailleur and 6 speeds (or what have you).

So, I resort to measuring. Is it as simple as 'if the width appears to be 3/32", that's what I need'? Or are there subtleties in the dimensions of the chain and the chainring that I need to look out for?

1 Answer 1


If it's 1/8" then a 3/32" chain will have to be jammed on to mesh, or not fit at all. The simple thing to do if possible is take a chain from a derailleur bike or even a scrap and physically try it.

1/8" chains and cogs/freewheels tend to go longer and on a singlespeed application, there is no downside (other than weight) to running them alongside a 3/32" ring, so you could also just get 1/8" for the rest of it regardless of what the ring is and call it good.

  • That "test it with a chain scrap" thing is exactly the kind of trick I was hoping for. Turns out the chainwheel is 3/32", but I went with 1/8" cog and chain as you recommend. Thanks!
    – hairboat
    Commented Apr 20, 2019 at 18:38

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.