Date:         Mon, 26 Nov 2007 12:48:40 +1300
Reply-To:     Andrew Grebneff <andrew.grebneff@STONEBOW.OTAGO.AC.NZ>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Andrew Grebneff <andrew.grebneff@STONEBOW.OTAGO.AC.NZ>
Subject:      Re: Friday: Best + Stupid=Oxymoron
In-Reply-To:  <E1Iw7c3-0005HA-17@elasmtp-galgo.atl.sa.earthlink.net>
Content-type: text/plain; charset=iso-8859-1; format=flowed

>The question says the "wheel" and not the "tire", so I'm not sure haw
>that affects the mixture.  Probably not.
>
>DM&FS
>
>At 11:16 AM 11/24/2007, Bob Stevens wrote:
>
>>"If the tire is under inflated, does the wheel make more revolutions
>>per> mile? Less? The same? Why?"
>>
>>More. Because the underinflated tire is essentially turning with a
>>reduced diameter. Taken to the extreme, the rim diameter is quite a
>>bit smaller than the combination of rim + tire. Let enough air out
>>of a tire and it creeps toward having the rolling diameter of the rim.
>>
>>Bob


Bob's right. As the tire loses pressure the center of the wheel sinks
toeard the ground, effectively reducing the rolling radius of the
tire/wheel assembly. This reduces the effective (not actual) rolling
diameter. Thus it has make more revolutions to cover the same ground
distance. note that this is more important at low speeds eg around
town... as speeds rise acceleration due to angular momentum causes
the tire to expand radially, reducing the effects of underinflation
to a degree.
--
Andrew Grebneff
Dunedin
New Zealand
Fossil preparator
Seashell, Macintosh, VW/Toyota van nut
‚ Opinions stated are mine, not of the University of Otago
"There is water at the bottom of the ocean"  - Talking Heads