Cyclocross - low gearing

I'm working with a bike shop on a cyclocross bike. I like it, except the compact double gearing. I'm wondering if you all have any suggestions.

I'm not racing this thing, but I am climbing some single and double track (by riding, not running up on foot!) and a lot of hills. With my old bike, by the end of the day, I want to use the granny gear to climb, using 24x24 or 24x21 (with 26 inch wheels).

This new compact cross bike has a lowest gear of 34x27 with 27 inch wheels.

What are my options?

- go to a triple - apparently this might be expensive, most of the drivetrain would need to be swapped

- get a 13-29 cassette - cheaper, but still not quite as low as I'd like

Anything else?

A cassette with a 30T low will get you about the same as the 24x21 gearing you were used to, you'll need a 36t to get as low as the 24x24. You'll likely be able to run a road rear der with a 30t, but a 36t will take a long cage mtb der.

I should have also mentioned that this is a 10 speed (Shimano 105).

30t sounds nice. But is there a 30t 10 speed cassette? 10 speed jumps from 29t to 32t (edit: on Sheldon Brown's web site).

Yes, and on the Harris Cyclery (Sheldon Brown's employer) page you'll find the "century special" which is a 14-30.

Personally, looks like you're needing a mountain bike rather than a cross bike. But, you could run mountain bike gearing on it with the STI's. I converted one of mine to it for some strange reason. Then quickly converted it back. I used a Deore crank, front and rear derailleurs and a 12-34 cassette. There wasn't much I couldn't climb with it, but it wasn't that great for the road. I think I picked everything off ebay for about $150-200.

Edit: opps, that cassette is a 9 speed. I wonder if you could simply add another cog and spacer to it? Bet you could.

IRD makes, even though Harris doesn't list it, 10s cassettes with final of 28, 30, 32, 34 teeth.

http://www.interlocracing.com/cassettes_steel.html

I only know one 36t and it's a 9s.

Another option may be to switch to a "Super-Compact" Double, using a triple crank but with only two rings, double shifter and double derailleur, you could get down to a much smaller inner ring.

Yeah, this is unusual. I do use a mountain bike now. I wanted a light mountain bike (cross country, maybe) with drop bars, but cross bikes seem to be the closest beast unless I go to something much heavier - like a Fargo.

I guess I should have also mentioned that this is going to be my commuter bike. To stay off the numbered routes during rush hour, I take snowmobile trails and washboard dirt roads. That's 1/3 to 1/2 of the route (the fun part!). The rest of the route is pavement.


Anyway, if I could make that CS922 Century Special 13-30 a 12-30 by adding a cog, that would be just about perfect!

Well, the triple wasn't an option. And the store didn't want to put anything lower than a 27t on the bike, they said they didn't want to support it if it shifted poorly. I bought the darn bike anyway. Call me a fool.

Also, no go on adding a cog to 9 speed. Maybe with friction shifters, but not with STI. Spacing is different.

So. I read that Shimano will release a 10 speed 11-34 mountain cassette (http://cycle.shimano-eu.com/publish/content/global_cycle/en/nl/index/news_and_info/news/dyna-sys__shimano.html).

Is the MTB Shimano cassette compatible with road? I'm trying to decide if I should buy a 11-28 Ultegra and tune it myself or wait for the wider range MTB cassette.

Shimano is going 10sp. Sram already has a 10sp MTB group. Also, the Sram Apex group has a 11-32 cassette. I would do a MTB der and a bigger cassette and leave the crank be.