Re: [CR]From what I'm understand, this shouldn't be true...


Example: Framebuilders:Alex Singer

Date: Mon, 5 May 2008 18:44:30 -0700
From: "Kurt Sperry" <haxixe@gmail.com>
Subject: Re: [CR]From what I'm understand, this shouldn't be true...
Cc: "Classic Rendezvous" <classicrendezvous@bikelist.org>
In-Reply-To: <30607.93654.qm@web32608.mail.mud.yahoo.com>
References: <cd45da8c0805051636q7c18e664hbaa9675eee6b86d1@mail.gmail.com>


Another useful way of looking at is to realize that the footprint or contact patch area increases as the tire deforms under more weight and that at a given pressure, that footprint will be essentially proportional to the load / tire's internal pressure. This is why at a given pressure and load the footprints will be roughly equal for skinny and fat tires, which is non-intuitive and helps explain why wide tires are likely to have no more- and probably even less as the necessary deformation is smaller in relation to the tires' shape- rolling resistance in actual practice. Fat tires do however *look* slower than skinny ones so are a harder sell to people who don't know better, which is most people.

Kurt Sperry Bellingham, Washington USA

On Mon, May 5, 2008 at 5:20 PM, Peter Tutty <peter_tutty@yahoo.com> wrote:
> Don,
>
> What has happened in simple terms is this:
>
> As you put you 260 lbs on the tyres, the bottom of the tyres deformed (spread outwards), but the internal volume (space) within the tyre/tube did not change. As the volume was not reduced, the existing air pressure was not raised.
>
> To put it another way, in order for the air pressure to have been increased, the volume(internal space) of the container (the tyre/tube) would have had to have been reduced. In fact the container (the tyre/tube) was just reshaped.
>
> Peter Tutty
> Village of Londonderry
> City of Penrith
> County of Cumberland
> State of New South Wales
> Commonwealth of Australia.
>
>
>
>
>
>
>
> Don Williams <donwilliamsjr@gmail.com> wrote:
> But it is...
>
> Hi All...
>
> I have, in the last few years, grown to a "very stout" 260 lbs.
> Hopefully cycling will relieve this in a reasonable time frame. But I
> digress...
>
> I'm riding Continental Giros tubular tires at around 95-100 psi. As I
> ride them, they don't >seem< soft to me.
>
> Confounded and looking for another data point, I sat on the bike and
> had my wife check the tire pressure and it really didn't seem go up...
> This info did not help!
>
> As far as I know I do not live outside the jurisdictional boundary for
> the laws of gravity or thermodynamics...
>
> Any one have a idea where I'm going wrong?
>
> All I wanted to do was determine if I'll be able to ride on a pair of
> Veloflex Criteriums...
> Without blowing them to smythereens...
>
> Don Williams
> Woodinville Washington USA
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