[python] Re: another newcomer
- From: George Durbridge <gdurbrid@xxxxxxxxxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Thu, 25 Jan 2007 07:47:08 +1100
Henry was right the first time. It really is odd that using a tyre with
a stiffer body gives higher rolling resistance, but inflating the tyre
to a higher pressure (which also makes it stiffer) gives lower rolling
resistance. Above all when it means that a highly regarded road tyre
like the Stelvio performs worse than a Fat Boy.
But it does seem to be true. For instance, Tioga Comp Pools used to
have the lowest rolling resistance of tyres in the 406 size, provided
you inflated them to 100psi. (Current Comp Pools may not withstand
100psi - use Greenspeed Scorchers instead.) And narrow performance
tyres such as Primo Comets and Schwalbe Marathons have no better rolling
resistance at 100psi than the old Comp Pools, perhaps not as good (they
are better at resisting punctures, though).
However, Fat Boys and Comp Pools are wider than the tyres we are
comparing them with, as well as less stiff, and it has been suggested
that width is the relevant factor. From the performance of Maxxis
Hookworms, which are very stiff, 50mm wide and very heavy to ride, I
suspect that stiffness is more important than width.
On Wed, 2007-01-24 at 17:50 +0100, Olaf Johansson 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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--
George Durbridge
+61 3 9481 3500
+61 409 413 945
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