I got a “new to me” coker with 125 cranks on it. I struggled with mounting, riding and face plants for a while. I was sure I would get the hang of it if I just struggled through. Hills were nearly impossible, just staying on was a challenge.
Then in a stroke of belated brilliance, I put on 150 cranks. Suddenly free mounts were nearly automatic, riding a pleasure and hills (up and down) were both possible again.
Just a little more leverage was all I needed. I wonder what 160s would do? 175s are probably out of reach for my diminutive legs.
If you have a coker, you could buy a set of larger cranks for pretty cheap just to play. Some people like larger cranks and don’t feel like it takes away from their experience at all; 175’s do seem a little too big but you may try 160-165’s and find out that they suit your riding style/terrain better
I like 150’s on mine because I ride lots of hills and the 125’s and 137’s I had on there didn’t feel right. I don’t really notice the length when going faster but I’ve only gone about 17mph for anything longer than a few feet.
If you’ve got a single speed then you probably don’t want to go much longer than 150. If you ride a lot of steep hills then maybe 165’s would be a good fit. 175’s would probably be awkward and would limit your ease and speed on gentle terrain. I ride my 36" guni mostly with 165’s. I love them. The control and power I get from that length suits my environment and riding style well. But they definitely are not as fast on the flats as my 152’s, even when I’m in high gear.
Square taper cranks are cheap. Buy some and play around with them. It’s all about fun.
I’m using dual 165/137 cranks on my 36". At first 137mm took some getting used to; hills were a little tougher and mounting when tired was difficult. After a few weeks of using only the 137mm position mounting is easier and the easy-to-spin feeling hasn’t diminished. The 165mm position feels much slower than the 137mm (i.e. it is noticeably more effort to spin at the same speed) but the extra leverage is great when going off-road.
That’s true, but with the available gearing on bikes top speed is limited more by strength (how high a gear you can push) than by how fast you can spin the cranks. It seems that the trade off between the leverage of a longer crank and ease of spinning a shorter crank is largely avoided on a freewheel, multi-geared bike.
On a singlespeed uni (in this case 36 gear inches), speed is more often going to be limited by your RPMs and many find that shorter cranks are easier to spin at a given speed.
My 36er came with 150s and that’s what I used for a couple of months. Then I decided to try 125s and I just couldn’t get used to them. Free mounting was 10x harder and when I finally did manage to mount, I felt like I had no control. So I went back to the 150s.