All this talk leads to another question:
If I run helium in my tires, will I reduce my unsprung weight?
:-)
Wendy Hart
----- Original Message -----
From: "Bill Babcock" <BillB@bnj.com>
To: <BillDentin@aol.com>; <cartravel@pobox.com>
Cc: <fot@autox.team.net>
Sent: Tuesday, July 23, 2002 9:53 AM
Subject: RE: Tyre Pressure/Temperature
| Hmmm. It's been a long time since I studied the theory, but as I recall
| the ideal gas law refers to a dry, ideal gas, which air is not. If you
| wanted to really calculate this change (and I don't) you would need to
| compute partial pressures for each gas and add them all together. Then,
| since air always has a substantial amount of water vapor in it you'd still
| be fairly far off since water vapor acts differently than gas.
|
| It is kind of entertaining to think about this after all these years of
| ignoring physics (and chemistry)
|
| -----Original Message-----
| From: BillDentin@aol.com [mailto:BillDentin@aol.com]
| Sent: Tuesday, July 23, 2002 6:14 AM
| To: cartravel@pobox.com
| Cc: fot@autox.team.net
| Subject: Re: Tyre Pressure/Temperature
|
|
| In a message dated 07/23/2002 7:43:54 AM Central Daylight Time,
| cartravel@pobox.com writes:
|
|
| > Subj:Re: Tyre Pressure/Temperature
| > Date:07/23/2002 7:43:54 AM Central Daylight Time
| > From:<A HREF="mailto:cartravel@pobox.com";>cartravel@pobox.com</A>
| > CC:<A HREF="mailto:fot@autox.team.net";>fot@autox.team.net</A>
| > Sent from the Internet
| >
| >
| >
| > Ok, I tried to be quiet, but my chemical engineering background won't
| > let
| > me.
| > Air in your tires (or nitrogen, argon, hydrogen, hellium, whatever)
| obeys
| > the
| > ideal gas law, PV=nRT. The tire volume is fixed, so the absolute
| pressure
| > increases in direct proportion to the absolute temperature. Let's say
| you
| > have 20 psi in your tires at 70 degrees F. The absolute temperature is
| 70
| > +
| > 460 = 530 degrees R and at sea level the absolute pressure is 20 +
| > 14.7 = 34.7. If the temperature drops to 50 deg F (510 deg R), the
| > pressure will drop to 34.7(510/530) - 14.7 = 18.7 psi. If the
| > temperature increases to 130 deg F (590 deg R) during a race, the
| > pressure goes to 34.7(590/530) - 14.7 =
| > 23.9 psi.
| >
|
| Amici:
|
| This stuff is great. I am memorizing it verbatim, and plan to use it a
| cocktail parties. While I am totally unqualified, I love to talk Hi Tech.
|
| Can anyone tell me how VIAGRA works. Someone told me it was 2% nitrogen,
| .5%
| argon, 3% hydrogen, 6% helium and 88.5% Fix-a-Flat.
|
| Seriously, I appreciate this thread. We've been playing with tire
| pressures
| for years, and while we look really cool with our clip boards, pyrometers,
|
| and tire gauges.....truth be told..... we're still just 'playing with tire
|
| pressures'.
|
| Years ago the big muckity muck in BFG'S Competition Department (I forget
| his
| name), lectured me on tire pressures for about twenty minutes, and then
| said,
| "In the final analysis it is VERY PERSONAL. You have to run what feels
| good
| for you."
|
| I think the latter is especially true at our level of competition.
| FORMULA
| ONE we ain't.
|
| Bill Dentinger
|
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