Originally Posted by Ken Cox

I've used a number of different cogs, too, with the exception of Phil Wood's cogs, and, to me, EAI cogs seem the best, by far, and Soma...well...I didn't like my Soma cog.

I have a thing about prime numbers, and in terms of cogs and chain rings, that means 13, 17, 19, 23, 43, 47, and 53 teeth.

This winter, I've also discovered the charm of riding at a much lower gear inch than I had ever anticipated.

I presently ride at 59 gear inches.

For those not familiar with gear inches, the typical factory fixie, with a 16t cog and a 48t ring, has about 78 gear inches.

I've ridden has high as 82 gear inches, and I need to ride at 72 gear inches or below in order to ride without a brake (I always ride with a front brake).

Further, I have always intuited that the greater the number of teeth in total, the more mechanical efficiency one experiences.
I couldn't prove this until just recently, when I picked up a book on mathematical proofs and the book addressed this very subject.

At any given gear inch, the more teeth one has, the more mechanical efficiency, or smoothness, if one wants to think of it this way.
At some point, though, the increased weight negates the increased smoothness/efficiency.

Anyway, I have 53 tooth chainring that I like, and I ride it with a 19 tooth cog.

How cool if I had a 23 tooth cog, for 60 gear inches and 23 skid patches (even though I don't skid).