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Good ratio for singlespeed 'cross races? (x-post w SS board)(1 post)

Good ratio for singlespeed 'cross races? (x-post w SS board)GlowBoy
Oct 6, 2002 5:03 PM
I've never raced before, but today I watched our local races for the first time, and Gawd I've got to get in on the fun. And I want to do it singlespeed! The elevation changes (at least on today's course) looked quite doable on an SS and derailleurs were looking like more trouble than they're worth. Fortunately, support for SS 'crossers is good here: I saw 1 in the beginner class, 1 in masters, and 10-12 in the separate SS class.

I will definitely be racing beginner class, and will be in for the fun of it, not to win. I've already set up this bike for SS commuting and trail riding, and am now trying to figure out what would be a good ratio for 'cross racing.

Right now my chainrings are 38t and 48t, and I have 15, 16, 18 and 20t sprockets lying around. Within reason this gives me the following options:

  • 38:18 is 2.1:1, good for 17 mph at 100 rpm. I did a 2-speed metric century this summer and this was my climbing gear: great for the climb up the Lorane Hwy out of Eugene but spun out way too easily on the flats, even in town. Maybe too low for the 'cross course too?

  • 38:16 or 48:20 are both about 2.4:1, good a hair over 19 mph at 100 rpm. I cruised around Portland's Leif Erickson Drive (gravel, easy grade) on the 48:20 a bit this summer and it seemed like I could get going good and fast but still handle at least a little climbing on it.

  • 38:15 is 2.53:1, yielding 20.3 mph at 100 rpm. Haven't ridden this gear. Might be getting too tall? I dunno.

  • 48:18 is 2.67:1, 21.4 mph at a comfortable spin and maxxing out a bit over 30. I commute on this gear, and have done 2 paved metric centuries on it. Definitely seems too tall for 'cross, at least at my level.

Any advice? I'm leaning towards the 48:20 ... sound reasonable, or should I go for something shorter or taller?

And hey SS_MB7, you mentioned running 42:18 (2.33:1). How's that working out? Do you think 2.4:1 is too tall with 700c wheels?

- Dan