Crank length should, in theory, relate to your thigh length, but seeing as you generally only get four crank lengths, it’s not very scientific. Track bikes usually have a lower bottom bracket height and so shorter cranks were fitted to give clearance on the track, and 165mm became the norm.
Personally I’ve always used 170’s on my road and fixed gear bikes, just to keep it simple.
Crank length should, in theory, relate to your thigh length, but seeing as you generally only get four crank lengths, it’s not very scientific. Track bikes usually have a lower bottom bracket height and so shorter cranks were fitted to give clearance on the track, and 165mm became the norm.
Personally I’ve always used 170’s on my road and fixed gear bikes, just to keep it simple.