General Discussion Triathlon Talk » proper crank length measurement Rss Feed  
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2010-09-15 12:21 PM

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Subject: proper crank length measurement
So to determine proper crank length, it seems there is some mixed information.

Using this method to measure my inseam http://www.precisiontandems.com/inseam.htm , I used these two calculations to determine proper crank length. 

http://www.machinehead-software.co.uk/bike/cranks/cyclist_crank_length_calculator.html

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

My inseam seems to be about 31 inches, but its telling me i need 170mm cranks and a 163mm crank....... one of these must be horribly wrong....

Who else can provide information on determining proper crank length??  My current crank is 170mm.  Don't seem to have any issues with it, but its getting pretty worn.






2010-09-15 12:29 PM
in reply to: #3100227

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Sensei
Sin City
Subject: RE: proper crank length measurement

I guess I wouldn't worry about it?

First, they don't make 163 crank arms...  Smallest they go is 170 (save for custom).  So you can't make a change anyway.

Second, if you don't have an issue with 170, why change?

2010-09-15 12:31 PM
in reply to: #3100254

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Subject: RE: proper crank length measurement
You can find 165's, though they're fairly rare.
2010-09-15 1:26 PM
in reply to: #3100265

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Subject: RE: proper crank length measurement
briderdt - 2010-09-15 11:31 AM

You can find 165's, though they're fairly rare.



agreed, i ride a set of 165s from shimano, took a few days of looking around but found a pair.
2010-09-15 1:28 PM
in reply to: #3100227

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Subject: RE: proper crank length measurement
Because if i find out that 172.5 is my proper length, then that opens up options on used cranks.
2010-09-15 1:31 PM
in reply to: #3100429

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Subject: RE: proper crank length measurement
funkyd04 - 2010-09-15 12:28 PM

Because if i find out that 172.5 is my proper length, then that opens up options on used cranks.



let me save you some time.

You'll get as many answers on the right length as their are options for cranks out there.

If you have no issues with the current cranks, i would not switch unless you have a good reason for doing so.


2010-09-15 1:40 PM
in reply to: #3100429

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Sensei
Sin City
Subject: RE: proper crank length measurement
funkyd04 - 2010-09-15 11:28 AM Because if i find out that 172.5 is my proper length, then that opens up options on used cranks.


Fair enough!  But your options were 163 and 170, but you might go to a 172.5 despite both the recomendations?
2010-09-15 2:53 PM
in reply to: #3100227

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Subject: RE: proper crank length measurement
Mainly it comes down to your flexibility.  If you are in aero...a longer crank will bring your knee closer to the chest/elbow.
2010-09-15 2:55 PM
in reply to: #3100643

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Subject: RE: proper crank length measurement
bmcgee - 2010-09-15 1:53 PM

Mainly it comes down to your flexibility. If you are in aero...a longer crank will bring your knee closer to the chest/elbow.



flexibility is only one (and a very very small one) of the many things that go into picking the right crank.


I just dropped from 172.5 to 165.

I have no real flexibility problems, but i wanted to change my position.
2010-09-15 4:23 PM
in reply to: #3100648

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Subject: RE: proper crank length measurement
newbz - 2010-09-15 2:55 PM
bmcgee - 2010-09-15 1:53 PM Mainly it comes down to your flexibility. If you are in aero...a longer crank will bring your knee closer to the chest/elbow.
flexibility is only one (and a very very small one) of the many things that go into picking the right crank. I just dropped from 172.5 to 165. I have no real flexibility problems, but i wanted to change my position.


care to elaborate on some?  If a 172.5 will in fact fit me, i'd hate to pass up an awsome deal on a used sram red crank.
2010-09-15 5:07 PM
in reply to: #3100833

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Subject: RE: proper crank length measurement
funkyd04 - 2010-09-15 3:23 PM

newbz - 2010-09-15 2:55 PM
bmcgee - 2010-09-15 1:53 PM Mainly it comes down to your flexibility. If you are in aero...a longer crank will bring your knee closer to the chest/elbow.
flexibility is only one (and a very very small one) of the many things that go into picking the right crank. I just dropped from 172.5 to 165. I have no real flexibility problems, but i wanted to change my position.


care to elaborate on some? If a 172.5 will in fact fit me, i'd hate to pass up an awsome deal on a used sram red crank.



i ride shorter cranks because they let me ride a position i want to be in, where longer ones would not. it was that simple.

again, fitters will put you on diff length for diff reasons. just like you'll find people liking them for diff reasons.

they feel diff, and you may change how you ride a bit.

If you go longer or shorter, you will have to change your saddle height around to make up for that diff in length.


2010-09-15 7:19 PM
in reply to: #3100227

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Subject: RE: proper crank length measurement
so more aggressive positions would generally call for a shorter crank i'm assuming?  I ride relatively aggressive right now.
2010-09-15 7:38 PM
in reply to: #3101074

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Subject: RE: proper crank length measurement
not on their own, but i was at the limit of what i could do with my bike (bars all the way down, saddle where it should be).

So the shorter cranks let me raise the saddle some.

I naturally ride at a higher cadence anyway, so this seemed like a good idea to try. i like it, climbing has suffered some, but riding on the flats in aero is more comfortable.

i'm dropping the bars even more tomorrow with a new stem and its just been a trial.

It also lets me get over the top of the pedal stroke a bit easier.

I know others my height that ride 175s, so it really is a personal pref for the most part.
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General Discussion Triathlon Talk » proper crank length measurement Rss Feed