<div dir="ltr">So what are the variables in this equation for tire pressure?<div><br><div>1. Ambient temperature - which is constantly changing (I'm a meteorologist)</div><div> I seriously doubt after about a minute of driving that the ambient temperature </div><div> will be a significant contributor to tire temperature and pressure</div><div>2. Friction - tire on the road (or track) surface</div><div> Also probably a very small contribution until......</div><div>3. Tire construction - flex of the sidewalls going through turns</div><div> Clearly a more significant contribution to tire temperature. Watch the F-1</div><div> and Indy car boys swerving to build up tire heat.</div><div>4. Finally, the tire compound itself - its ability to hold heat once it has been heated.</div><div><br></div><div>The warmer a tire gets, the warmer the air in it gets and the higher the pressure in</div><div>that air. Simple physics.</div><div><br></div><div>I would think that all of these factors enter the equation but to what extent I do not know.</div><div>The racers will have a better read on this methinks....</div></div></div><br><div class="gmail_quote"><div dir="ltr">On Tue, Aug 28, 2018 at 12:37 PM Ron Soave via Spridgets <<a href="mailto:spridgets@autox.team.net">spridgets@autox.team.net</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="auto">What you ultimately care about is the contact patch and tread behavior at temperature. It depends on the tire, not the car. The manufacturer should list that somewhere on their website. <br><br><div id="m_3909257459238851569AppleMailSignature">Ron Soave</div><div><br>On Aug 28, 2018, at 7:39 AM, Rick Fisk via Spridgets <<a href="mailto:spridgets@autox.team.net" target="_blank">spridgets@autox.team.net</a>> wrote:<br><br></div><blockquote type="cite"><div><div>Allen,</div><div id="m_3909257459238851569AppleMailSignature"><br></div><div id="m_3909257459238851569AppleMailSignature">Not wanting to start anything here, but your tire pressure recommendations don't make sense to me. I've never seen the recommended tire pressure is at 32 degrees F spec in a manual anywhere. ??? Seems to me the tire pressure should be the same no matter what the temperature is.</div><div id="m_3909257459238851569AppleMailSignature"><br></div><div id="m_3909257459238851569AppleMailSignature">For every 10 degree F rise in air temperature the pressure in your tires will rise about 1 psi and fall 1 psi for every 10 degree drop in temperature. So to maintain the car manufacturer's recommended tire pressure you should reduce the pressure when the temp goes up and raise it when the temp drops.</div><div id="m_3909257459238851569AppleMailSignature"><br></div><div id="m_3909257459238851569AppleMailSignature">Why would you always add 5 psi to the recommended pressure? Seems to me the car manufacturer probably knows best when it comes to recommended tire pressures for their cars. </div><div id="m_3909257459238851569AppleMailSignature"><br></div><div id="m_3909257459238851569AppleMailSignature">Rick</div><div id="m_3909257459238851569AppleMailSignature"><br>Sent from my keyboard</div><div><br>On Aug 27, 2018, at 10:39 AM, Allen Hefner via Spridgets <<a href="mailto:spridgets@autox.team.net" target="_blank">spridgets@autox.team.net</a>> wrote:<br><br></div><blockquote type="cite"><div><div dir="ltr">Don't forget that the recommended tire pressure in the manuals is at 32 degrees. You usually add 1 PSI for every 10 degrees above freezing. Nobody seems to know that anymore. The manuals just say ## PSI cold. I always just add 5 PSI to the recommended pressure. <div><br clear="all"><div><div dir="ltr" class="m_3909257459238851569gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div>Allen Hefner</div>
<div>Norristown, PA</div>
<div> </div>
<div><em>Current:</em></div>
<div>2016 Subaru outback somewhere</div><div>2006 Chebbie</div>
<div><em>Former:</em></div>
<div>1963 Sunbeam Alpine Series III</div>
<div>1967 Triumph TR4A IRS</div>
<div>1964 VW Type I</div>
<div>1967 VW Type II</div>
<div>1967 Rover 2000TC</div>
<div>1977 MG Midget (Sniff!)</div></div></div></div></div><br></div></div><br><div class="gmail_quote"><div dir="ltr">On Tue, Aug 21, 2018 at 1:40 PM John Farley via Spridgets <<a href="mailto:spridgets@autox.team.net" target="_blank">spridgets@autox.team.net</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="auto">I am running 175/70 R13s on my 1275+ Bugeye with front disc brakes. What are folk’s recommendations for tire air pressures & lug nut torque?</div><div dir="auto">The manual seems low for both. </div><div dir="auto">Thanks, John F.</div>
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</blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><span style="font-size:small">-- </span><br style="font-size:small"><span style="font-size:small">Cheers!!</span><br style="font-size:small"><span style="font-size:small">Jim Johnson</span><br style="font-size:small"><a href="https://www.facebook.com/MET105/?ref=bookmarks" style="color:rgb(17,85,204);font-size:small" target="_blank">UHI Aviation Meteorology</a><span style="font-size:small"> Adjunct Professor</span><div style="font-size:small"><a href="http://www.ejssm.org/" style="color:rgb(17,85,204)" target="_blank">E-Journal of Severe Storms Meteorology</a> - Chair</div><div style="font-size:small"><br>"Tact is the ability to tell someone to go to hell in such a way that they look forward to the trip." <br>Winston Churchill</div><br><div style="display:inline"></div><div style="display:inline"></div><div style="display:inline"></div></div></div></div></div>