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Old 10-16-2011, 12:05 PM   #11 (permalink)
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I've been using 40mm deep rims front and rear. I seem to notice adifference between these and box style rims--although it may all be weight and placebo effect.

I've been away from racing for acouple years and hope to retun in '12. I've been very good and I'm sure Santa will bring me a new set of wheels, I just want to know what I should ask for.

My thought was a deep V in the front and a light box mag ie: American Classic magnesium in the rear. The front gets the clean airflow and it should make a difference. The rear wheel gets a wierd and changing flow dut to everything in front of it and apair of moving legs. Short of a full disc, I don't see anything likely to clean up the exiting air. A full disc weighs about 950-1200 grams the mag wheel about 480.

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Old 10-22-2011, 02:24 AM   #12 (permalink)
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Very creative....Its the start of the future
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Old 11-10-2011, 07:46 PM   #13 (permalink)
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Quote:
Originally Posted by bikin' Ed View Post
I've been using 40mm deep rims front and rear. I seem to notice adifference between these and box style rims--although it may all be weight and placebo effect.

I've been away from racing for acouple years and hope to retun in '12. I've been very good and I'm sure Santa will bring me a new set of wheels, I just want to know what I should ask for.

My thought was a deep V in the front and a light box mag ie: American Classic magnesium in the rear. The front gets the clean airflow and it should make a difference. The rear wheel gets a wierd and changing flow dut to everything in front of it and apair of moving legs. Short of a full disc, I don't see anything likely to clean up the exiting air. A full disc weighs about 950-1200 grams the mag wheel about 480.
From http://en.wikipedia.org/wiki/Racing_bicycle:

Moment of inertia changes result in a decrease in watts of between .004 and .022%, while lower mass provided between .2 and .46%, and better aerodynamics provided between .6 and 1.8% decrease in wattage. Therefore, wheel moment of inertia effects are neither noticeable nor important.

Emphasis added.

Edit - I think this might be the paper the Wiki article took the info from: http://biketechreview.com/reviews/wh...el-performance

Here's a quote from that paper:

So, what do all these numbers mean? It means that when evaluating wheel performance, wheel aerodynamics are the most important, distantly followed by wheel mass. Wheel inertia effects in all cases are so small that they are arguably insignificant.
How can it be that wheel inertial forces are nearly insignificant, when the advertisements say that inertia is so important? Quite simply, inertial forces are a function of acceleration. In bike racing this peak acceleration is about .1 to .2 g’s and is generally only seen when beginning from an initial velocity of 0 (see criterium race data in Appendix D ). Furthermore, the 0.3kg/0.66lb difference in wheels, even if this mass is out at the rim, is so small compared to your body mass that the differences in wheel inertia will be unperceivable. Any difference in acceleration due to bicycle wheels that is claimed by your riding buddies is primarily due to cognitive dissonance, or the placebo effect (they paid a lot of money for the wheels so there must be some perceivable gain).

Last edited by Patrick; 11-10-2011 at 08:23 PM..
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Old 11-12-2011, 10:39 PM   #14 (permalink)
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Here's some more very technical info about bicycle wheel aerodynamics from:

47th AIAA Aerospace Sciences Meeting Including The New Horizons Forum and Aerospace Exposition
5 - 8 January 2009, Orlando, Florida


Titled: An Aerodynamic Study of Bicycle Wheel Performance using CFD

By: Matthew N. Godo1
JMSI dba Intelligent Light, RutherFord, NJ, 07070
David Corson2
ACUSIM Software, Inc., Clifton Park, NY 12065
and
Steve M. Legensky3
JMSI dba Intelligent Light, RutherFord, NJ, 07070


http://www.acusim.com/papers/AIAA-2009-322-649.pdf


Jay

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