crank length for new bike

[KnottedYet]

I prefer 175's, so don't nobody ask me!

[DirtDiva]

Yeah, but you're taller than everyone else in this thread except perhaps the fella who started it.

[boy in a kilt]

At worst, she may get a tad bit of toe overlap. As long as she isn't prone to doing lots of track stands, she'll probably be ok. A quick way to check is measure from the center of the crank spindle out about 210mm (I'm guessing on the spindle to end of toe-box measurement). If you haven't gotten to the tire yet, she'll be ok.

The main difference she'll notice is the extra bit of torque she'll get when she pedals. The extra 5mm of lever arm may not seem like much, but it does make a bit of difference.

[VeloVT]

I'll share my experience, for what it's worth (maybe not very much, since I'm not the same size, and it doesn't address toe overlap issues at all). I'm 5'6". I have a 52 cm cx frame and a 54 cm road frame, both still with stock cranks. The 54 cm frame has 172.5mm cranks, and the 52 cm frame has 170mm cranks.

I notice the difference. Really. I wouldn't have believed I'd feel a 2.5mm difference but I do. I definitely prefer the 172.5 mm cranks. I feel I get considerably more power, especially on hills. Since I'm also thinking of switching the cx bikes triple for a compact double with slightly higher gearing, I'm considering getting longer cranks at the same time.

FWIW.

Oh, I'm also a size 39 shoe.

[Crankin]

Well, the shop put 170 cranks on my Kuota, so I tried them, after having 165s on my Trek. I hated them. I felt like I had to use a lot more energy, so off they went after 2 weeks. I am 5' 1" and my bike is 51 cm, with a sloping top tube. The shop owner tried to tell me that the longer cranks would turn me into a "climbing machine," but I am a spinner who always uses the easiest gear possible! Well, I do use the big ring at times, but too much just makes my knees hurt.
I guess it depends on what kind of riding she will be doing.

[Beane]

here's something interesting:

http://www.nettally.com/palmk/crankset.html

...But I think it's a personal preference/trial-and-error kind of thing.

[Eden]

I'm thinking if you are short with longer legs (especially thighs) that long cranks would be worse - my reasoning is, I have this body type and I already have to push my saddle back almost all of the way to get good knee position. If I had a longer crank I'd have to try to find even more set back. I'd also have to lower my saddle some, which depending on the kind of fit you are looking for could be good or bad. For me, I want to preserve any drop that I have so I don't want to have to put my saddle down at all.

btw I have 165's on all my bikes except for the kiddie cross bike that I recently aquired, which as 150 somethings on it.