Singlespeed Cyclocross Gearing

[lunacycle]

So, I've finally decided to take the plunge into the exotic world of singlespeed cyclocross. All of my other bikes are either singlespeed or fixed gear, so this just seems like the next logical step.

I'm planning to set up my rear wheel with a Surly bmx cog and a stack of aluminum cassette spacers. I have a Rennen Rollenlager chain tensioner on my ss mountain bike conversion that I'm going to borrow to take up the chain slack. I'm already running a single ring up front with an outer chain guide and a Third Eye Chain Watcher, so no modification is required there.

My question concerns gearing. I'd like to use either a 38x18 or 42x18 gearing, mainly because these are the sizes I have on hand. So I'm wondering what kind of gearing other singlespeed cx'ers are using, or if there is some magical do-it-all gear ratio for cyclocross. For what it's worth, It seems like the cyclocross courses here are getting faster and less technical, so I'm leaning towards the 42x18 gearing.

Any comments?

[2speedfiend]

I ran a 42x18 last year. Worked fine - not too tall for the ups, not too small for the flats - unless they were long ones, then I spun out.

[xccx]

i think you will be ok with either. lots of peeps seem to run 42x18. it sort of depends on your riding style...how much you like to spin, etc. you could also get a combo for the back...17 and 19, or 16 and 18...that would give you another option which might be good for different style courses.

http://sheldonbrown.com/harris/white-freewheels.html

what frame are u using and what rear brake setup are you thinking about?

[summerinside]

I've got a Surly Crosscheck that I set up at 40x18 (I like a quicker cadence). I recently lowered it down to 40x16 - a little bit quicker, but on really steep riding I'm grinding more.

[lunacycle]

To answer your question, xccx, I have a 2000 GT ZRX, with vertical dropouts, and I'm running Avid 10c cantilevers. I thought about springing for an Eno eccentric hub, but I didn't want to commit the money. Those freewheel combos look intriguing, however.

[gonesh9]

I've got a Crosscheck with 46X20 on the freewheel side of a flip-flop. Been going to the cross practices, and riding fireroads around here with it a lot lately.... it seems like just the right compromise gear. I guess that's pretty similar to your 42X18 gear. Probably depends on what kind of courses you'll be riding in your area.