Crank length?

[norcalbiker]

How would you know what crank length do you need? Is there any site for guidance? I mean, how would you know whether you 170 or 172.5?

TIA

[oldguy00]

How tall are ya?

[flickwet]

what's your inseam?

[norcalbiker]

It's actually for my wife.
She is about 5'-6" about 29 inseam.

[Waldo]

Lennard Zinn says inseam (real inseam rather than pant size) times 0.215. You may arrive at a pretty big number. Works for me, though, and I'm 6'1" and use 190mm cranks.

[oldguy00]

It's actually for my wife.
She is about 5'-6" about 29 inseam.

I'd personally recommend 170, which I believe would be pretty standard for someone her height.

[oldpotatoe]

How would you know what crank length do you need? Is there any site for guidance? I mean, how would you know whether you 170 or 172.5?

TIA

Put three people in a room and ask about crank length, get 4 opinions. No calculation of femur length(far more important than leg length/inseam or height) will give you an 'answer'. Later you mentioned it was for your wife, and if I sold ya a crank I would recommend a 170.

[shiftyfixedgear]

The Lenny Zinn multiplier is so far away from what many experienced riders choose that I would strongly caution against using it as a reference on choosing a crank length. Like a lotta rules of thumb, it might work for a few people but . . . I generally distrust recommendations made by people who are selling that same item (i.e. Zinn and cranks).

Don't ask a barber if you need a haircut <G>

[Waldo]

Zinn is not alone in his advocacy of longer cranks. My empirical experience after five years on the 190s is that they work for me very, very well. Much better than shorter cranks had for 20 years. Most "experienced riders" haven't tried to go with cranks using the Zinn formula. So, bashing it without trying it rings hollow. 40 million Frenchmen CAN be wrong.

[Ti Designs]

40 million Frenchmen CAN be wrong.

I need that line on a bumper sticker...


Crank length is more complicated than most people understand, and it really can't be looked at in isolation of all the other fit parameters. The pedal stroke is determined by three pivots, the hip, knee an ankle. Each has multiple muscle groups extending, contraction or stabilizing the joint. Then there are the limitations, most people don't have more than 110 degrees of range in their hip, so for someone without long femurs to run super long cranks means the body has to find some other way of compensating for the travel. And as odd as it may sound, torso length and upper body weight come into crank length as well. When I set up a bike I'm looking for a balance between large muscle groups - glutes and quads. With a longer torso, getting the center of gravity over the pedals so the glutes can support the body weight means increasing setback. More setback means more angle at the hip, and the limiting factor becomes getting that foot over the top without having to push it over with the other side.

This forum has a lot of people who run very long cranks. In over 20 years at the bike shop I've sold less than a dozen pairs of 180 cranks. I've only seen one person on the forum who uses really long cranks, and he seemed to turn them with such ease that I wouldn't have noticed had he not told me. The others I haven't seen on the bike so I can't judge - but I do have my doubts...

[Waldo]

Long cranks are not so bizarre or hard to ride as some people seem to think. My friend, who's a senior coach for Wenzel Coaching and a fitter, asked me during a fitting session to pedal my 190s one-legged and I could do it easily with either leg. That's not to toot my own horn, but to show that it's easier to ride them than conventional wisdom would lead one to believe.

TA has made 185mm cranks forever, though they're the only mainstream manufacturer committed to making cranks in 2.5mm increments from 162.5 to 185. FWIW, you can get a much better deal on the same long cranks from Tom Slocum at High Sierra Cycle Center (http://www.hscycle.com/) than from Zinn.

[dd74]

It's actually for my wife.
She is about 5'-6" about 29 inseam.
She's my same height and inseam. I ride a 170 mm. As a comparison, I used to ride a 172.5, but 170 feels better and spins a bit faster.

[dd74]

Repeat post -- sorry

[norcalbiker]

Thanks guys!!!

I think 170mm it is.

[RPS]

Then there are the limitations, most people don't have more than 110 degrees of range in their hip .... snipped......
OK, I'll bite. How do you come up with this number, or better said how do you define and measure it in order to come up with such a low number? :confused: