Crank arm length??????

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JN2Wheels
Posts: 219
Joined: Sat May 09, 2009 3:03 am
Location: Maryland

by JN2Wheels

Think what you like... and I'll disagree. Its not about the feel of the corner, its about the pedal grazing vs. the pedal catching. One is scary, the other will hop the bike and take you down. On the edge, those 2.5-5 mm will matter.

Although, either scenario is a mistake by the rider. If there is a danger of dragging a pedal, the racer shouldn't be pedaling through the corner anyway.

KLabs
Posts: 380
Joined: Wed Dec 01, 2010 4:29 am

by KLabs

fallzboater wrote:I'm "only" 6' 3" but have a 98cm cycling inseam. I've used 180s (Dura Ace, Record, XT, XTR) on all my bikes for many years. If I borrow or rent a bike with 175s it feels odd to me for about an hour and I feel like I'm not climbing as well, but I don't have data to back that up. My range of hip and knee rotation is less with 180s than most riders have with 170s. I'd try longer, but prefer to stock with commonly available parts and frames.

interesting... what is your cadence preference, rear wheel rim weights, etc...

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fallzboater
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Joined: Wed Feb 03, 2010 2:26 am

by fallzboater

KLabs wrote:interesting... what is your cadence preference, rear wheel rim weights, etc...


Average riding cadence is around 90, can be 100+ for good acceleration when racing. Climbing is typically around 70, lower if very steep. I'm able to spin up to about 120 without bouncing. I don't see how rim weights are relevant to crank length, that would effect acceleration only and to the same extent for everyone. My race weight is around 180 (too heavy, but I used to lift weights and was a college rower) and I use aluminum rims around 450g for reasonable durability while training. Most rear rims don't last more than a couple of seasons before I start getting cracks at the nipples, but I swap them myself, so it's not a big deal.

Oswald
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Joined: Thu Jan 08, 2004 10:11 pm

by Oswald

I am 175cm with long torso and short legs. I can definately tell the difference between 170 and 172,5mm. With 172,5 my right knee hurts and my pedal stroke feels less smooth. So I ride 170 on all of my bikes. I usually ride between 100 and 105rpm on average. To me that doesn't feel like a high rpm, but other cyclists do often comment me on my 'high' cadance. Back when I was racing, I could easily average 120 rpm on a Tacx training.
I would love to try a 165mm crank, but haven't put in the effort yet to source one.

kame
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Joined: Thu Jan 28, 2010 11:31 am
Location: Denmark

by kame

As mentioned before, this has been discussed to death in many articles and forums, so I'll just add my data points.

I'm 187cm tall, with relatively long legs, at ~93cm inseam. I use 180mm cranks on my MTBs and 175mm on my road bikes. I like it, but I cant really tell a big difference. There is a little more risk of ground strikes on the MTB, but you quickly learn to control the pedal position when cornering or going over obstacles.
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hjb1000
Posts: 265
Joined: Wed Sep 16, 2009 10:25 am
Location: Australia

by hjb1000

I've got a 32 inseam and I'm finding 175mm mtb cranks to be too long for my knees. Ideally 172.5 would be great, but most mtb cranks are available only in 170mm. Going to try 170's.
And try and keep the q-factor low too.

plag
Posts: 58
Joined: Sun Sep 07, 2014 4:16 am

by plag

We're talking millimeters here most won't even notice the difference .


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KLabs
Posts: 380
Joined: Wed Dec 01, 2010 4:29 am

by KLabs

plag wrote:We're talking millimeters here most won't even notice the difference .

millimeters, yes... so, should we say/talk the same about top tube length?

Also, we are talking rotation, so the length is at least doubled...

mattr
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by mattr

I can tell the difference between the 172.5 on my race bike (no 170s available this side of Christmas) and the 170s on my training bike. All other contact points are the same, to within measurement error.........

In hindsight I'd have gone to 167.5

And I do know of crit specialists who run short cranks on their crit bikes, and then additionally grind the ends off their pedals........

kulivontot
Posts: 1163
Joined: Sun May 16, 2010 7:28 pm

by kulivontot

Apparently the cross crankset had a 172.5 driveside/170 nondriveside.
I never noticed until I pulled it off to switch cranks.
$.02

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wheelsONfire
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Location: NorthEU

by wheelsONfire

I would like to check with you, the road bikers, what crank lenght you use and what inseam lenght you have.
I put this question since i am thinking of changing from 172.5 to 175mm.

My inseam is 87cm.
Bikes:

Ax Lightness Vial EVO Race (2019.01.03)
Open *UP* (2016.04.14)
Paduano Racing Fidia (kind of shelved)


Ex bike; Vial EVO D, Vial EVO Ultra, Scott Foil, Paduano ti bike.

singlespeedscott
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Joined: Wed Jan 11, 2012 12:37 am

by singlespeedscott

My inseam is 88.5cm and I run 175mm.

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kkibbler
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by kkibbler

77cm inseam, 170mm cranks

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Rick
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Joined: Sat Aug 29, 2009 4:30 pm

by Rick

Inseam: 33" (83.8cm) / 172.7 cm tall
I used 172.5 for years, then experimented with 175s and 180's, then went back to 170 all last year. Now back on an experimental kick with 180s. (Thanks, SRAM for inexpensive Rival cranks in 180!)
The "Zinn formula" of .216*838 = 181. Even his more conservative formula of .21 x 838 = 176

Even the jump from 170 to 180 seemed pretty subtle to me. But although it is subtle it is definite. Just like everyone says, 170s are easier to spin smoothly and 180s seem better for low cadence climbing. There are always too many confounding varables to know whether it really helps power output, but in the end it doesn't seem to make a significant difference. At least it doesn't seem to be decreasing power. We will see how it goes.

jpanspac
Posts: 159
Joined: Thu Apr 11, 2013 8:21 pm

by jpanspac

My inseam is 76cm. Last year I went down to 160mm cranks from 170mm, and liked it a lot. I had always had a problem with my thighs hitting my ribcage when in the drops, but the shorter cranks allowed me to raise my saddle and lower my stem and use the drops more. I also think it helped keep my legs fresher by reducing the extreme hip angle on the top of the stroke. Next year I'm going to try 165s to see if I can keep those advantages while getting a little more torque.
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by Weenie


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