47x19

When talking with other cyclists, particularly other fixie riders the subject of gearing often comes up. My usual ride has an odd but very specific gearing: 47 up front, 19 in the rear. Why?

The gain ratio (47 / 19) is just a hair under two and a half (2.47). Good for going up (and down) hills in San Francisco. 47 and 19 are both prime. This distributes the wear pretty evenly over the chain and sprockets. Any given link on the chain will hit the same tooth on the chainring every 893 revolutions, which is approximately once per mile with 700c (~27 inch) wheels.

Empirical evidence leads me to believe this ratio is as close to perfect as you can get for San Francisco, for a brakeless everyday fixie. It's equally good for banging around town or a paradise (Tib) loop.

Comments

May 18
7:06 PM
Edit

chuck q writes:

the frankenbike is a righteous ride. I run a 47x17 on a 1972 Schwinn Paramount track bike & go out for hours on rolling roads in upstate NY. I'm building up a singlespeed cyclocross bike with an EBB & would like to hear your thoughts about going with a split BB shell rather than a solid shell?
Cheers - Chuck Q

June 1
2:38 PM
Edit

ydnar writes:

The split shell has been great. The grip on the eccentric is on the full outer radius of the shell instead of N bolts, so it's probably more reliable in the long run. I'd definitely use a sealed BB (Phil's are good) though.

October 23
11:26 AM
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carleton writes:

I agree...47x19 is great for the Bay Area. 44x17 is also a really nice ratio.... and I like your Serotta.