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  #1  
Old 09-25-2017, 07:47 AM
n1ey n1ey is offline
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crankarm length - gearing

Hallo!
Slowly trying to build to my goal for more efficiency. I am wondering about torque numbers and thus gearing. Do people any have thoughts on which chainrings and crankarm length for a given torque number?

Which torque numbers are we supposed to achieve at your power zone 6? Perhaps as a cyclist with 3.5 w/kg?

I am wondering if I should go back to a 52 or 53 and go with a longer crankarm. I have a 50/34 on the front with 175mm cranks. Or do I have this as the wrong way? Go with a 48 or some cx ring and 180mm cranks?

My saddle to pedal is at 82.2cm with the 175mm cranks.

On an effort to take a very short KOM, I averaged 500 watts. GC calculated numbers at 300 N. This was around 100RPM.

Any thoughts to steer me in the right direction would be helpful.

bill
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  #2  
Old 09-29-2017, 07:45 AM
noahwcollins noahwcollins is offline
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I'm a coach with Carmichael Training Systems. Crank arm length is really based on preference of the rider. Not only that but you will find that with the longer crank, if you are a shorter person, you might eventually have some anterior knee pain.

That being said, I think you are putting too much stock in the numbers instead of focusing on efficiency alone (angular velocity)--cadence. Power numbers are great for training and comparison, but the only way for you to find out what cranks you should ride is to try them out and see how you like them. Shorter cranks are awesome for crits and fast accelerations...but of course the longer cranks allow for the torque you speak of.
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Old 10-04-2017, 07:45 AM
n1ey n1ey is offline
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Quote:
Originally Posted by noahwcollins View Post
I'm a coach with Carmichael Training Systems. Crank arm length is really based on preference of the rider. Not only that but you will find that with the longer crank, if you are a shorter person, you might eventually have some anterior knee pain.

That being said, I think you are putting too much stock in the numbers instead of focusing on efficiency alone (angular velocity)--cadence. Power numbers are great for training and comparison, but the only way for you to find out what cranks you should ride is to try them out and see how you like them. Shorter cranks are awesome for crits and fast accelerations...but of course the longer cranks allow for the torque you speak of.
I had 100 RPM on this effort that I selected as representative of one of my peaks. Would I be better to go for 90RPM? This isn't a crit. I don't think I ever will succeed in a crit. The speed out of the corners has been tough for me. I am holding in a nice steady road race.

bill
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  #4  
Old 11-02-2017, 02:01 AM
Kontact Kontact is offline
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Quote:
My saddle to pedal is at 82.2cm with the 175mm cranks.
Working backwards from these numbers, your inseam is only around 29". What are you doing on 175mm crank arms? You're going to screw up your knees.

And if that inseam number is wrong, your saddle is too low.
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  #5  
Old 01-08-2018, 12:13 PM
audiojan audiojan is offline
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Join Date: Jun 2011
Location: Greater Pittsburgh
Posts: 31
It really sounds like your cranks are too long... although it is a highly personal thing. There's very little correlation (if any) between gearing and crank length. Crank length has much more to do with femur length, fit (yes, crank length does impact fit, not only saddle height, but also drop) and then you need to add the person preference to that.

With your inseam length, I would guess you should be 165-170, but again, that's just a guess based on averages...
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