I am just in the process of doing up a bike and making it single speed, an old tourer for commuting – not mtb. I bought a singlespeed freewheel (18t) from Condor Cycles – the cheap one for a tenner. Having put it on the chain just doesn't seem to fit on the cog. I have tried the original chain (it was the original off an old 80's 10 speed Falcon). I have also tried a SRAM one I had kicking around but that is the same. It's as if the spacing between the pins on the chain is too long – it can't have stretched that much and the SRAM one was new so had no stretch? I have checked Sheldon Brown but he doesn't mention different chain types (pin to pin length rather than width). Are there different sizes or am I being being dim, or both? Ta.

Pics?

Seems odd that a new chain does not fit. Inconceivable (unless it is the width)

I think there was once some track kit with 10mm pitch but I doubt you've come across any of that. Otherwise, it's all half inch (unless it's very very worn)

width is fine. I'll try and get pics now.

Pitch, that's the word I was looking for. I'll measure.

ok, I'm being dim. Width of the inner links is the problem. Back to the shops…

YES!!!!!!!!!

*punches air*

pint of ale to the man with his fist in the air