Road Cycling - Crank Length Question

How can you tell if you have the right length cranks? I am 5'10", with a 30" inseam....save me the short legs jokes please. My bike currently has 172.5 cranks. I do a lot of climbing, and prefer to keep the spin high. Will 170's make a difference?

holy crap you have short legs! ;)

Yeah 170's do windup faster. It's only 2.5 but it's noticeable but fwiw, I'm a climber and spinner and prefer 172.5's (32in inseam)

If you ride a lot, you should notice a slight difference, but it's only 1.45% :)

Maybe you could get some cheap, 2nd hand 165s, and just whack them on for a try before you spend big bucks on some 170s.

One good thing about 170s is that you can pedal around corners :)

Hey sweet, I had not even thought about the cornering bit...maybe I will have to celebrate 170's with my first crit? AHAHA!

Dura-Ace used to come in 165, and occasionally you can find them used really cheap. 5.3mm per inch of inseam suggests your optimal length is 160mm or a little bit shorter than that. I know several women of 5'2" who have settled on 172.5, but I can't remember their inseams for sure right now. Think they were 30"? One of them who was an awesomely muscled hip-rocker used 175s for years, but she finally decided she was going to trash her lumbar spine and went to 170. The other went up from 170 to 172.5 and seems to be doing fine.

OTOH, you get a little more leverage w/the longer cranks, which may facilitate keeping the rpms up on climbs. What kind of cadence are you able to maintain, comfortably? If it's okay, I wouldn't switch unless you're experiencing knee trouble.

Better leverage means you can use a lower cog ratio, and turn slower. With shorter cranks, you gear down and spin up. The power you apply, amount of work you do, and your speed of travel are identical.
You are about the right size for 170 as your "normal" length. You can ride longer or shorter for different styles
Check out the graph at
http://www.cranklength.info/crankCalc.htm#crank%20length%20graph
and see also
http://www.nettally.com/palmk/crankset.html

Better leverage means you can use a lower cog ratio, and turn slower.
Or, spin up in the same gear! I prefer to keep rpms up when climbing as much as the next guy, but resistance is what slows me down.

No3, If your floor-to-crotch measurement is 30", than maybe 170s are a better fit, and may allow you to spin high rpms smoother. But that's the reason to get them... bigger cogs on the cassette will do more to keep your cadence up on climbs than shorter cranks. And save you a bunch of money over new cranks, too.