[python] Re: another newcomer

home@xxxxxxxxxxxxxxxxx wrote:
I guess on a larger wheel more rubber is envolved in the flexing than on a smaller wheel.
But saying that a softer compound would give less rolling resistance ... uh, uh. I am not yet willing to buy that. Anyone who let out 20 psi from the bike's tyre will notice an increased amount of sweat on their forehead. 


olaf




On 24 jan 2007, at 14.14, dirk.bonne@xxxxxxx wrote:


Henry Thomas wrote:

dirk.bonne@xxxxxxx wrote:

FYI: there has been documented measurements related to this. Check out
this pdf:

    http://www.ligfiets.net/redactie/meetligfietsengels.pdf

Dirk
Dirk, thanks for sharing this with us, it was a very interesting read. There isn't a lot of test data like this that I have found which is specifically dealing with recumbent.
I am a bit confused about the tires. As I read it, larger rims (26") and firmer rubber compounds are better at higher pressures (110psi). However I thought that the Specialized Fat Boy was softer than the Schwalbe Stelvio Kevlar, or is that not the case. 
<moz-screenshot-1.jpg>
I read the opposite out of this paragraph and thus no contradiction. The supple rubber compounds are better. The stelvio material is stiffer and also has a worse performance.
What I think is interesting is that extreme height differences between seat / BB are not needed. From 15 -> 25cm is no much different in power. So you can just as well use 15cms (more ergonomic). note, the measurement was made for seat angle of 21degrees. 

Dirk



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While agreeing with you in the main, I think there may be a gray area where a thin layer of stuff that's not so stiff may have the effect of counteracting a negative rough surface effect, though I have neither numbers nor specific theory for this idea /*i.e., the stiffness of the surface of the tire may transmit energy into vertical motion which takes away from forward speed.*/ 


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