Before I begin – I’ve read the previous threads on this and am aware of the 2:1 idea and have seen other recommendations of 32:18 for Glentress and the like.

My issue is that I began with the singlespeed idea for commuting – 7 miles undulating with no really long climbs or anything steep (other than a short sharp rise). It’s now mutated into a ‘this could be fun off-road’ project as well.

So…I’m trying to decide on a gear ratio for the bike. I’m aware that what works off-road won’t really work on it but don’t mind switching the rear cog over for that – question is what size chainring to go for?

A 32t gives the choice of the ‘standard’ 32:16 and dropping to 32:18 for hilly rides (or even lower) but is limited at the top end to around 14mph using a 32:14 with a cadence of 80rpm.

A 36t gives a much better top end but loses out on the low gears. And a 34t seems like it might either be the best of both…or the worst of both.

Anyone have any experience?

The limit is really a combination of how fit you are, your leg power, how fast you can comfortably spin and the terrain.

The only way you can find out what is best for you and the terrain is to experiment. Everyone is different and some prefer to spin while others stand up and stomp.

FWIW on 26″ wheels, I vary from the equivalent of 32:16 to 44:18 depending on the circumstances.

BTW a 34t will only make a small difference either way but you could try something like a dual freewheel HERE or two chainrings at the front and two cogs at the back to give a spread of 4 ‘gears’ if you want to swap between road and offroad gearing.

If you only have one bike, and also have a reasonable amount of on-road in your commute, you will be bored silly on 32:16. I run 32:15 on my singlespeed for off road duties (Glentress and the like), as it gives a little bit more speed when I need to nip across town on the bike.

With skinny CX tyres on, I run either 32:12 or 32:13, but that would be tough going off road.

I’d start at 32:15 if I were you, and see how you get on from there.

If you are going any smaller at the back, you might want to increase to a 34t chainring instead, to give better chain wrap. 34:16 is quite close to 32:15 for example.