[OHPV-list] Crank Arm length

[tha_capt]

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Sent: Wednesday, April 05, 2006 9:00 AM
Subject: OHPV-list Digest, Vol 31, Issue 4


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> Today's Topics: crank arms ? ? ? which length  ? ?
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Hi Chris ~

Due to having had intimate "painful" experience with crank arm length I will 
contribute to this highly controversial topic.

First I congratulate you on addressing this topic early in the season. Mid 
season changes can mean serious tendonitis issues.

What ever you decide to go with "do - not" go longer crank arm lengths 
mid-season.

Now for the reasons "why" you would want to change?

Is it because of the length of your legs or do you want more power?

I'm finding now that I'm on a low racer as well as my trusty Gold Rush, that 
crank arm lengths vary from the position of the bottom bracket in reference 
to the rider. As strange as it may sound bottom bracket "BB" height has 
everything to do with how much movement the rider has in the saddle. A lot 
of Gold Rushes have cool back seats which give in the back modestly when 
pushing hard on the pedal stroke hence a shorter crank arm sometimes is 
required for a complete "power stroke." Those of us who ride with carbon 
fiber seats with no give other than padding can ride with a crank arm fitted 
for constant X-seam fit.

Note: I'm guessing that Tweety has experienced better climbing with her new 
bike with shorter crank arms, because of the lower BB position. This would 
make her more powerful compared to her Aero with a higher BB. The same case 
can be said of the Gold Rush's vs the high BB lowracers. In general, the 
lower the BB - the more power to the pedal.

Longer crankarms also can provide more torque which equates to more power. 
The longer crankarm logic proved worthy for me when four years ago when I 
changed from 170mm to 175mm. on my Tour Easy. I noticed immediately that I 
could gobble up the climbs easier than with the shorter 170's. It was no 
placebo - the additional torque was there without doubt. I really paid the 
price though. I made the change mid-season. My knees and tendons had already 
acclimated to the 170's and they told me they didn't like the 175's "at all" 
with a severe case of tendentious that tools weeks to recover from. I 
immediately put the 170's back on for the rest of the season with slow 
recovery coming just before Cycle Oregon - "Whew"

Later that winter I couldn't get the climbing benefits of the 175's out of 
my head and wanted the extra torque badly. So I put the 175's back on and 
with careful pre-season riding, grew to absolutely falling in love with them 
as climbers. The down side was I lost RPM's in my cadence while flat land 
cruising with my short legs. They were awesome for roller hills for as I had 
the power and torque to power up and over the hill top with momentum. 
Loosing the cadence did concerned me however.  I finished up the season on 
the 175's not wanting to take a chance on tendentious again. The third 
season I reasoned that perhaps a set of 172.5's would be a compromise of 
power and "my" normal cadence. And they indeed did - they have given me both 
power and cadence, so for now the 172.5's are my preferred crank arm length. 
They have provided me with the best of both performance needs.

I suggest the 170's would be the best crank arm length to start with. Next 
season you will be more in touch of what your rider performance is and what 
you "feel" you need to adjust to enhance your personal performance. Notice - 
I said "feel." Listen to your body "Grass Hopper" It will tell you what 
changes you should make.

Note: - - 170mm vs 175mm = approx. 1/4 inch. in length. When that quarter of 
a inch makes a full circle - that measure equates to approx. 1/2 inch for 
the full circle. That's a bunch of difference in length to adjust to mid 
season.

later ~