jesus, unless you're the hulk don't bother. I'm not the strongest mind you, but i'm pushing 48X16 in new york city (around 81 to 82 inches on 27 by 1 and 1/4 tires) and it's a little overboard with steep bridge climbs (at least i'm not the only person gearing down due to wburg bridge nside ped walk closing...). I had my bike converted and that's the gear they put on there and I just thought I was a ***** bc I couldn't spin it (bc I didn't know any better). I made myself get used to it and I'm definitely very much stronger for my effort, but I'm dropping about 7 to 9 gear inches on my new bike to learn to spin a bit better and be more efficient (and build my stamina). Currently even on bridge descents I feel I've got a little bit of gear left to push, and I don't feel the speeds I can hit on a rare long, uninterrrupted flat are worth the loss in acceleration. unless you live on a prairie and there's very little or no stopping, or you're some track hero looking for your first street bike, you're just gonna kill your knees and possibly yourself. can't tell you how many times in the beginning i pulled out to try to make it bt some oncoming cars only to realize i wasn't going anywhere and almost getting hit...