What should determine your crankset size?

[Piccolo]

I'm a tall rider at 6'4" and 180lbs. Currently I'm riding on a set of 175mm 10-speed Ultega cranks. I believe they're something like a 53/39(I can't remember cause my bike isnt with me at the moment). Someimes I feel like I'm using a lot of energy and just spinning my wheels on long climbs and wonder if a little more leverage would help since my legs are much longer than most of the competition.

I'm hoping that someone who has ridden 180mm cranks could offer their opinion on the matter. Are they really better for taller riders? Also, what combination of teeth would suit the longer cranks better? At the moment I'm leaning towards a 54/42T combo.

 

[DiabloScott]

I'm a tall rider at 6'4" and 180lbs. Currently I'm riding on a set of 175mm 10-speed Ultega cranks. I believe they're something like a 53/39(I can't remember cause my bike isnt with me at the moment). Someimes I feel like I'm using a lot of energy and just spinning my wheels on long climbs and wonder if a little more leverage would help since my legs are much longer than most of the competition.

I'm hoping that someone who has ridden 180mm cranks could offer their opinion on the matter. Are they really better for taller riders? Also, what combination of teeth would suit the longer cranks better? At the moment I'm leaning towards a 54/42T combo.

Thumb rules and ratios typically don't apply to folks on the extremes of height. Here's Lennard Zinn's advice column on the subject. Zinn is a tall guy who uses 202mm cranks!
http://www.insidetri.com/train/bike/articles/1875.0.html