Flat Fla does not provide much opportunity for climbs, but in mid-state there is an area around Claremont with lots of great hills, at least for FLA. Each summer we visit family in upstate NY and I bring my bike and do some nice rides up into the Heilderberg Mts.

My bike came with an 12-25 which worked well for me, but I struggled on many of those hills, and had to stop. When I got my new BWW BlackRace set, I put 11-23 on it, no help for the hills. Finally I got an 11-27 for the old wheels, and use them for the hills. Works great! Now I do hills with out stopping, and don't spin out on descents.

I also put an 11 -28 on the tandem when I got a spare set of wheels. Tandems don't climb very well. It helps.