Single Speed Questions

[charliedid]

I'm slowly working on a commute-ish/ gravel bike that will run fat tires tubeless and see plenty of dirt and crushed limestone .... and have been going back and forth regarding setting it up SS.

I currently have or will have a set of Bontrager wheels (9/10/11) and a SRAM Rival AXS crank 1X and 8 bolt spider which is of course 12 speed. I know Surly and Wheels Manufacturing make SS spacer kits but curious what other option are out there. It's been a long long time since building a SS bike so what do those of you who run single speed have to suggest?

- Chain and cog issues with wide/narrow ring on the crank? Can I just run a 9 speed chain? Does a rear cog exist for a narrower chain. My research has been spotty.

- No real hills here in Chicago but will take this thing to local single track for kicks. Crank has a 40T on it but what do I want for a cog? I was thinking 16 or 17T

Thanks for the knowledge and advice.