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Old 06-24-08, 11:58 PM   #1
fthomas 
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Check Your Crank Length

Has anyone experimented with changing your crank lengths. I was asked some interesting questions at the LBS this past weekend and decided to get some better answers. Most manufacturers just put the "standard" length on, whatever that is.

Here is a link to an interesting article:

Check Your Cranks
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Old 06-25-08, 12:03 AM   #2
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Here is another site that I found:

Bicycle Crank Length

I think that I am going to go with a shorter crank on my touring bike.

Any thoughts or experience?
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Old 06-25-08, 12:08 AM   #3
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We've had several discussions on this topic over the past year or so. I've seen some going in the past week.

I currently have 170mm on three bikes, 165 on a fourth, and 155 on my recumbent.

I think my favorite lengths are 165 on an upright bike and 155-160 on bents, but am not certain yet.

Here's a crank arm length calculator. It tends to yield results that seem too short for most people.

http://www.machinehead-software.co.u...alculator.html
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Old 06-25-08, 12:11 AM   #4
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I use 167.5

Works for me.
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Old 06-25-08, 12:15 AM   #5
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Bike companies lilke to put 175's on most bikes, except for their smallest bikes which get 170's.

Personally, I think a lot of people use crank arms that are too long, and think they need them long to generate more power. Lab tests indicate that few riders actually generate more power with long cranks. In fact, some recent tests really surprised some racers when they saw that their maximum power curve was generated when they used 150mm cranks.
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Old 06-25-08, 12:23 AM   #6
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I remember reading some material from Sheldon Brown when he experimented with shorter crank arms. He was surprised to find them more efficient than the longer cranks he had been using for many years.

This article doesn't contain those particular statements, but it does capture the gist of his findings:
http://www.sheldonbrown.com/cranks.html
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Old 06-25-08, 04:20 AM   #7
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Over the last couple of years I have changed down to the shortest length (still 170) that the cranks I use come in. I have no hard data, but my impression is positive, especially on a roadbike with a steady spin.
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Old 06-25-08, 09:04 AM   #8
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Quote:
Originally Posted by fthomas View Post
Here is another site that I found:

Bicycle Crank Length

I think that I am going to go with a shorter crank on my touring bike.

Any thoughts or experience?
This appears to be the same formula that Lennard Zinn (framebuilder, VeloNews tech wizard, and all around tall guy) espouses. Since I have a 36" inseam, this would put me on 197.5's (yes, one NINETY seven). Considering that this isn't exactly a common size, and considering the knee problems I've experienced when trying 180's, I've stuck with 175's. They work fine, and I can turn 'em at 100+ rpms all day, no prob.

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Old 06-25-08, 09:27 AM   #9
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29" inseam, 175mm cranks work for me.
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Old 06-25-08, 10:20 PM   #10
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I've got a 35.5" inseam and ride a 61cm frame. It has 175's on it for the last 12k miles or so, but I'm going to experiment with some 172.5's that I recently bought to see how it works with my knee. (due to major surgery followed with staph infection many years ago I can't bend that knee much past 90*)
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Old 06-25-08, 10:27 PM   #11
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We ladies out here are disappointed in the responses, considering the title of this thread! Phooey!
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Old 06-25-08, 11:08 PM   #12
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Originally Posted by CitiZen View Post
We ladies out here are disappointed in the responses, considering the title of this thread! Phooey!
Shucks, my 175 crank is only approx 6.9". Boo - Hoo
Remember this is the 55+ Forum, so it's not about what you got but more about how long you can cycle.
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Old 06-25-08, 11:15 PM   #13
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We could start a thread about shoe size.
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Old 06-26-08, 12:22 AM   #14
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Why oh why has it degenerated to this?
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Old 06-26-08, 12:29 AM   #15
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It hasn't really degenerated very far yet.
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Old 06-26-08, 01:38 AM   #16
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I'm the instigator of one of the crank length threads that resurfaced recently when I got an even shorter set of cranks, 175>170>160mm.
Are Your Cranks Too Long?

You might peruse the initial post and then skip to the end.
In a nutshell- I'm 6" with about a 31" inseam, bad R, knee and 60 years old. Let's say my L. knee is "used".
After going to 170's, there was GREAT improvement in speed & stamina. I came to the conclusion, that my bad knee didn't have enough range in motion to handle 175's. I was "sapping energy", carrying my R. knee "over the top".
I was looking for 165's to take the experiment further, but didn't get there because of budget considerations.
A couple weeks back, I ran across these on a different BF forum and though Why Not? If they didn't work, I wasn't out much $.
http://www.nashbar.com/profile.cfm?c...20ATB%20Cranks

My cadence increased approx. 10 more RPM, but my "apparent" gearing has changed very noticeably.
I ride flat pavement on my "commuterized" 86 Rockhopper. When "cruising, I'm on the middle (38T) ring and using the 15 or 16T cog in calm conditions. I currently have a custom cassette with 13-14-15-16-17-19-21-24 cogs. I now wish I had a 12T top cog, so I could add an 18T for a bit more flexibility for head winds.
My conditioning isn't really up to snuff though, so in a couple weeks I may be able to turn one gear higher?
I have ALL those high gears on the big ring I can't use!
I think 165's would probably work best for me.

Anyway, if you have a square taper BB, there is a cheap method to find out what 160's will do. Be prepared for a VERY different sense of gearing though.
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