I have a stock 2009 Jamis Aurora.
I'm looking to modify my gear set-up to make climbing hills with large loads a little easier on my knees, as I constantly find myself wishing I had one or more low gears. The specs say the crankset is an FSA Vero Forged 50/39/30 with a length of 175mm. The casette is a 9-speed SRAM Powerglide 950 (11-32). I read on a couple forums that some people had switched out their 30 tooth front sprocket for a 26 or 24, to help out with steep climbs and heavy loads. However, when I called a couple bike shops, they expressed concern that it wouldn't be possible and compatible with the front derailleur.
So I had a couple questions for bike experts since this is my first time really looking at gear systems -
1) Would changing from a 30T to 24 or 26T make a tangible difference on climbs?
2) How do I figure out whether the rest of the bike components will tolerate a 24 or 26t sprocket in the front?
3) Finally, any other solutions for this problem that one might try?
After incredibly helpful advice from folks in this thread, as well as consulting a number of LBS, I have successfully swapped out the 30 for a 26, without losing my STI levers and without any other problems. The secret lies in adding a 'chain watcher' to help guide the chain back onto the granny if it comes off. Some other adjustments to the front derailleur are also necessary. But with a competent bike shop, it's doable. I haven't climbed with a load yet (this weekend), but from use so far, it shifts smoothly into the granny (but you have to take care you're somewhere in the middle of the rear cassette when doing so), and shifting back up to the middle is also not an issue, though it takes a little longer than before and must be done delicately. With the granny, you shouldn't use the smallest 3 or 4 cogs in the back. Otherwise it works like a charm. Bike shop said it'd probably work just fine to switch the cassette to a 12-34 instead of 11-32 if I wanted lower gearing, too.