The toughest hills we've ridden up would be 8 miles, 3000' of total climbing with short stretches (1/4 mile) 13-14% and longish (2 miles) at 10% or so. We currently have 24t chainring and an 11-32 cassette on our daVinci, but I've been thinking of changing the cassette to 11-36. The cooler it is the better we climb since the captain doesn't cool well at higher temperatures.

The biggest challenge for us is not blowing up on really steep, shorter pitches which is where the 36t cog might come in handy. The long climb described, above, has a short pitch of at least 16% at the very top and we can't get up that riding.

Our very modest climbing ability limits us to 100K organized rides with no more than 3500' of climbing or perhaps an occasional century with a bit more.