Cyclocross - Changing granny gear on tricross sport

I'd like to put a smaller granny gear on my stock tricross sport - a pretty major tinkering job for me. How can I find out
a) What's the smallest chainring I can put on that will work with the derailleurs
b) Where to get such a chainring - LBS said they could order something in, but presumably I can do it cheaper by ordering directly myself.
c) How to put it on.

According to Specialized specs, the cassette is "Shimano HG-50, 9-speed 11-34t" and the chainrings "50x39x30T". The derailleurs are Deore LX, "long cage" and Tiagra. I think I'd like to put a 26 on, matching the Surly LHT gearing.

(We don't do cyclocross here, but I use this bike for touring, and found the lowest gear was a struggle for long climbs when loaded)

Thanks,
Steve

I seem to remember seeing a 24 tooth somewhere, but a 26 would be fine too. Figure out what the BCD is on the small ring before you order. You'll need to pull the crank arm off to replace the ring. If you don't have the tools, let your LBS do it. I know some of the shimano cranks can be pulled with only an allen wrench (105, external bearing BB), but in all likelyhood you'll need a crank puller. If you have not done it before, find someone to show you. It's easy to destroy a crank arm if you botch it.....


http://www.parktool.com/products/detail.asp?cat=26&item=CCP%2D2

Looks like FSA only goes down to 30. Might be able to put someone else's chainring on with no problem. I had a 28 on a bike with FSA cranks on it, but I got it off EBay.

Wow, with a 24 and a 34 on the back, it might be faster to just push it.

>Wow, with a 24 and a 34 on the back, it might be faster to just push it.

Yeah, I know, but I'd rather ride. It seems kind of ridiculous, but I'd still rather be able to drop down to super low gear to get the heart rate down a bit while pushing **** uphill, then crank it up again etc.

Anyway, sorry to sound like a total noob, but once I figure out the BCD for the chainring is, any 26 tooth chainring with that BCD will fit? Any difference between manufacturers? I'll probably go to the local nonprofit bike workshop for help fitting it, just want to make sure I order the right part.

(Guess I should have started this in the mechanics forum...)

Steve

I think that as long as your BCD is right and you're not putting something like Campy on a Shimano crank or vise versa, you should be ok. Some manufacturers use the same BCD, but their holes are off a little so you can't use one brand on another crank.

It's your bike, if you want that sort of gearing, go for it. You know what you want to do.