Originally Posted by Salamandrine

Usually swapping out rear cogs is much easier and more effective. One tooth back there is worth 3 or 4 in the front, on average. I was going to say something about 45/16 but figured you picked it for a reason. Yeah, it's pretty high for a 1 speed. 42/16 is more typical, for fit bike enthusiasts...

45/20 or ~61 inches is a good starter gear IMO. Depends on terrain and fitness. 45/21 I feel is a little on the low side. If it's all flat terrain 45/18 is probably going to be better.
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