[python] minimize rolling resistance, wheels tires air pressure
- From: Tom <zzed28@xxxxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Wed, 24 Jan 2007 12:48:29 -0800 (PST)
--- Tom <zzed28@xxxxxxxxx> wrote:
> Hi, I believe that the reason that taller
> wheels have less rolling resistance in general
> is
> due to the fact that they have to distort less,
> to give the contact patch. The contact patch
> which is dependent upon the overall weight and
> the pressure of air in the tire. Flexing a
> tire,
> takes energy from the pedaller, and more flex
> means more energy to input. Thats why taller,
> wider, flatter tires have less rolling
> resistance, a bigger contact patch with less
> overall tire distortion. The contact patch is
> determined by the weight and the pressure, if
> the
> total weight is two hundred pounds, then two
> tires at one hundred psi will give a contact
> patch on one square inch ,,each ,,by
> definition.
> The hardness of the rubber is not the relevant
> factor in this afaik, the overall compliance of
> the tire in its entirety against the pavement
> is
> what will count. That means that the more
> compliant casing, plus tread rubber, the less
> the
> rolling resistance. From over fifteen years
> and
> forty thousand miles on recums, thats been my
> experience. I personally am a fan of taller,
> flatter treaded tires for my own bikes since
> they
> dont have to distort so much against the
> pavement
> to provide a good contact patch. Tom
>
>
> --- Olaf Johansson <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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>
>
>
>
>
>
>
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