dleccord

im 5'5" and ride a 50cm. is 170mm cranks okay?

rpeterson

My girlfriend is 4 inches shorter than you and happy on 172.5mm cranks, you'll be fine.

Paul01

I'm 5-5.5 and spin fast on 170mm cranks. New bike, arriving Friday, will have 165 mm.

idoru2005

I know someone who is pretty tall (close to 6') and rides a large frame. He rides with PowerCranks with arms set to 110mm. He does this to get more aero - basically the shorter cranks allow him to raise his saddle a lot. Apparently this does not impact his ability to climb. In fact he's racing the Everest Challenge with that setup.

jgrosser

I'm the same size and have had 2 professional fittings. In each case, I was set up with 170mm cranks.

DropDeadFred

lol...i read this and thought you were trying to pick up women...."any shawtys in hurrrr"

DropDeadFred

A/S/L pic? lulz

lylepwns

I'm 5'3 and prefer the feel of 170mm cranks. The only benefit I see of 165mm cranks is no/less toe overlap if you are running standard 700c tires.

zonatandem

My wife/stoker has been riding tandem with me since 1975.
She's been using 170mm cranks and is 4' 10 3/4" "tall".

adriano 

i ride 160mm. 49.8cm effective top tube. shawties rejoice!

dleccord

^wow specs? i'd like to ride something liek that as a commuter bike. how come you had to run the rear derailleur cables like that?

adriano 

i wanted to keep them out of the way from muck and for carrying. a realistically shallow seat tube and steep head tube, no cheating the top tube short.

on slicks.

valygrl

5'2", 47cm bike w/505 ETT, 170 cranks, 40 bars

Wesley36

I run 155mm cranks, and I love them. Advocates of short cranks cite the following advantages:

(a) more RPMs for the same foot speed (pedaling in smaller circles)
(b) knee flexion - this is probably the main reason I have come across. If one does squats, it becomes very clear that when the knees are flexed beyond 90 degrees one loses power as opposed to when the knees not flexed beyond 90 degrees. The idea with short cranks is that one can apply power more efficiently throughout the pedal stroke, as opposed to having a zone of the pedal stroke where one's knees are excessively flexed and therefore unable of generating the same power. Further, deep knee flexion aggravates knee problems for many (especially those with problems related to muscles or connective tissue).

Interestingly, testing with power output and different crank lengths shows the highest power output at 145mm (see https://www.powercranks.com/cld.html), although the difference between 145 and 170 is not statistically significant.

Paul01

Loenard Zinn's formula

Try multiplying your inseam (in millimeters) by 0.21 or 0.216 to get a range of crank lengths appropriate for you. See below for more on this.

https://www.zinncycles.com/cranks.php

carpediemracing 

I run 175s, have for a while. I ride with a 65 cm (on 175s) saddle to center of BB height, 65.5 cm with 170s, wear 30" inseam jeans.

Crank length is a personal preference. I ran 167.5s for a long, long time, when I was significantly faster. I never managed 165s okay. 170s for a long time too, then 175s pretty consistently since 2003 or so. I tried 170s to find lost speed but it killed me, I even spent a whole year on the 170s with dismal results.

DScott

No, it didn't.

Because of this. If it lacks statistical difference, it's not different.

All this "study" shows, if anything, is that 145 and 170mm cranks are both different in power output from 120 and 220mm cranks, and NOT different from each other.

Science is a mutha...

Wesley36

Alright, if you want to be pedantic, 145 cranks did have higher output, but according to statistical tests, it is not clear that the difference is significant (ie that it was not the product of random variation). It is true that the null hypothesis (there is no difference between 145 and 170) is not disconfirmed, but it is not true that the tests showed no difference.

To say the difference is not statistically significant does not mean they are the same, it means that the difference could be random chance. Could be random chance does not mean is random chance. But you are right, the only clear conclusion is that 145mm and 170mm cranks produce more power than 120 and 220mm cranks.

DScott

No, it means exactly that. Those power numbers are not different, and saying they are is wishful thinking.

The appropriate statistical tests tell you whether the two sets of numbers are the same, or are not the same. In this came, they are the same.

If you can't prove the study's hypothesis, you HAVE to accept the null hypothesis (that there's no difference). You can't say "well, there is no difference in my study, but I want to believe there is, so I'm not going to accept these results and will continue to believe what I want, in spite of what the numbers say." Well you can say that, but then you'd be wrong.

Bottom line, if you went by these results, you should be able to generate the same power on cranks that range from 145 to 170mm in length. Not a great advertisement for the PwerCrank product, if that's what they're selling.

Wesley36

The study was cited by Powercranks, but it was conducted by an independent academic (Jim Martin, University of Utah). And I think we agree on the conclusion, but again, if you insist on being pedantic, the power numbers are different, but this difference is not statistically significant. The same means just that- that they are the same, not that they fail to differ in a way that is statistically significant. Science is about precision, rigour and being systematic, and these two claims do not have the same meaning.

A study that has a larger sample could very well find statistically different power differences, therefore- and this is the core of science- we do not want to draw premature conclusions. The discussion is not closed. The scientific conclusion is not "we can conclude that there is no difference" the scientific conclusion is "more research is necessary". And yes, this is why "science is a mutha".

DScott

Sigh.

If they're not different, to an acceptable level of statistical certainty, they are the same. That is the very definition of precision, rigour, and being systematic. The core of science is not drawing unwarranted conclusions, premature or otherwise. You were.

There's always room for more study, and the results might end up looking different with more statistical power, that's for sure. Probably not though, given this study and their conclusions:

https://www.ncbi.nlm.nih.gov/pubmed/21311357


Nice back-pedal, though...

CaptainHaddock

I know this is a year old, but that is so fuskingfunny! I haven't seen the A/S/L tag in like 10 years!

Paul01

Still here and still short.

EdIsMe

I was just pondering this question a few days ago.

I'm 5'5", 30" inseam and ride a 49cm (51.5cm tt). Cranks are 165, stem is 100.

It seems most bikes come with 170mm cranks as the minimum sizing. Even with the 165 cranks my legs contact my torso while in aero tuck...

Blossom

I'm 5'4" and I run 165 cm cranks. I mostly do it so that my knees make less contact with my belly and my stomach is happier. I'd consider going smaller, but it is ridiculously hard to find mid-to-high end 165 cm and the last time I checked, I'd have to go custom to go shorter. So 165 is where I'm at.