crank length

[Crankin]

I'm 5' 1" and I have 165 cranks. I tried 170s when I got the bike I have now, and I hated them! I felt like I had to make a huge extra effort to pedal. The shop owner thought it would "unleash my power" but I quickly told him to get over that notion.
I had 165s on my other 2 road bikes, too.

[OakLeaf]

I'm 5'3" - not exactly sure of my inseam, but petite pants are usually a tad short for me while misses (except very low rise) are unwearably long/tall.

I run 165s. I tend toward patellofemoral dysfunction anyhow, and back in the day I had a couple of nasty exacerbations brought on by 170mm cranks (although I learned to stretch my knees before every ride, and that helped a lot). When I built up my race bike I put on 165s, and wow, what a difference both in comfort and in the ability to spin at high cadence.

A couple of years ago when I first returned to road biking I demo'ed a bike with 167.5mm cranks. Although I only got about 150 miles on that bike and didn't get to tweak the fit in any depth (and it was the first time I'd been on a road bike in 12 years), those cranks still seemed too long for me. At any rate I felt I needed to set the seat height too high, to compensate. I didn't even realize they were 167.5s until much later when I started bike shopping and spec'ed out the one I'd demo'ed.

Can you test ride a bike with shorter cranks, just to see?

[VeloVT]

It's amazing how you can really feel a few mm difference. I'm 5'6", 31.5" inseam. I have a bike with 170s and a bike with 172.5s, and I can tell the difference. I prefer the 172.5's because I get better leverage -- it's noticeable all of the time but particularly on hills. I suppose it's a tad easier to spin faster on the shorter cranks, but the 172.5's allow me to spin as fast as I need to (normal cadence on 172.5's is around 90-100; when I get really tired at the end of a windy ride, I might ride in lower gears and spin between 100-110).

When bike shopping I often feel lucky (perhaps even grateful) that I'm very average sized (that is, I'm not petite). I am on the small end of the range where it's reasonably easy to find components to fit (and it drives me nuts how few models of bars come in 38cm, and that my size XS, WSD bike came stock with 40s), but I think it's still much easier for me than for many smaller women.

[HillSlugger]

I don't feel any real difference between 170's and 172.5's on my two road bikes but I had to switch out the 175's from my commuter bike as I was getting knee pain.

[madscot13]

sometimes I'm just surprised at the difference 2.5 mm will make

[KatyLady]

At 5'4", I have a 30" inseam and wear petite slacks. But because I have long femurs (not uncommon for women) I ride a 170 crank very comfortably.

[sgtiger]

5' 1 3/4" w/26" standover, the builders for my custom Rodriguez reccomended 170m cranks for me. Besides taking the standard standover measurement, the LBS guys took another measurement with me kneeling to get my femur-to-tibia ratio. Turns out my femurs are way longer than my tibia. Who knew? I think shoe size went into consideration too. My knees are definitely happier now than when I had 165m cranks. Just so you know my current bike's geometry is way different than the bike I had with the 165m cranks on them, so that may make a difference too.