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I for one can't think of an explanation for this startling
phenomenon. Obviously, the ambient air pressure is less at
altitude--known as 'adiabatic lapse rate' to nerds and
pilots--which, theoretically could cause the tires to expand,
increasing their volume and lowering the pressure (according to the
Ideal Gas Law). But, I doubt steel-belted radial tires expand or
contract much, but air pressure in fixed volume goes up about 1psi
per 10degF IIRC.<br>
<br>
Was there a 40degF difference in temperature between Portland and
Big Bear (California has been pretty warm the last few weeks, which
I can attest to since our A/C is on the fritz)? Also, temps vary
when tires are warmed by the sun or friction with the road, so if I
can't check pressure completely in the shade I'll under-fill the
tires in the sun by half a degree. So, my guess is a significant
difference in air temps, and asphalt absorbs a lot of heat which
gets transferred to the tires (Portland = (often) cloudy and cool;
SoCal = (often) sunny and hot).<br>
<br>
<br>
<div class="moz-cite-prefix">On 5/24/2021 8:20 AM, Jean Caron via
Healeys wrote:<br>
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<blockquote type="cite"
cite="mid:DM6PR17MB2507BA238E145706046CEAC9D1269@DM6PR17MB2507.namprd17.prod.outlook.com">
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<p class="MsoNormal">Sounds like you have one of those rare
wheels with self-adjusting pressure, I wonder when these
became an option and on what model !!!!!! LOL!</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Jean</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Sent from <a
href="https://go.microsoft.com/fwlink/?LinkId=550986"
moz-do-not-send="true">
Mail</a> for Windows 10</p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="border:none;padding:0cm"><b>From:
</b><a href="mailto:boyracer466@gmail.com"
moz-do-not-send="true">richard mayor</a><br>
<b>Sent: </b>May 24, 2021 9:28 AM<br>
<b>To: </b><a href="mailto:healeys@autox.team.net"
moz-do-not-send="true">Healeys</a><br>
<b>Subject: </b>[Healeys] Conclave tire air pressure change
trivia</p>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<div>
<p class="MsoNormal">My Healey tire pressures went from 29
psi here in Portland, Oregon, to 33 psi at Big Bear Resort
in California - 6,700 feet above sea level. I then
lowered my tire pressures to 29 psi.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Checked my tires today back in Portland
- 70 feet above sea level and all tires at 25 psi.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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