Date:         Tue, 11 Feb 2020 04:37:44 +0000
Reply-To:     Richard Koerner <rjkinpb@SBCGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Richard Koerner <rjkinpb@SBCGLOBAL.NET>
Subject:      Re: PSI and Bars, for tire pressure
In-Reply-To:  <BD016563-06D6-484A-8531-56434844DA9E@eoni.com>
Content-Type: text/plain; charset=UTF-8

 I think that is why it is always described on the recommended tire pressure in every manual and booklet as "Cold" tire inflation pressure.  Friction and rubber moving around creates heat, and resultant increase in tire pressure.   When you mentioned a 6-7 psi change on your 15 mile drive, I am assuming that is an increase in tire pressure.  

Right....temperature INSIDE the tire due to a combination of Ambient Temperature and frictional forces are what matters, and raises tire pressure.  Since it is all so confusing, that is why they recommend checking tire pressures with vehicle just sitting there, tires cold, ideally.  I go regularly to my Discount Tire Center for a Free air check; I usually walk over to a nearby store or something to let things cool off a little before the tire pressure check.  And...the reason for the "free" air check?  So they can stick their probe into the tread to measure thickness, and also inspect tire build date, in hopes of selling you a new set of tires.  Good for them!!  Still....they have these cool computer controlled inflation gizmos....I tell them "44 PSI, all around, including my spare" (valve stem sticks out through one of the holes on the underside clamshell holder)....and that is exactly what happens.
Works good for me.  And yes....I will buy my next set of tires from Discount Tires.  On both cars.  Free lifetime spin balance too.  I gave up on Costco a long time ago.
(For long time Listers...Just when you always thought there could never be another tire thread....ha-ha!)



    On Monday, February 10, 2020, 7:53:36 PM PST, Jim Arnott <jrasite@eoni.com> wrote:  
 
 I see about 6-7 psi change on my 15 mile drive to town. Temp doesn’t change much at all. (Alistair’s cheap TPMS.) It fits great on the ledge under the tach. I have to pull it out and throw it on the dash about once a week to charge.

Jim

> On Feb 10, 2020, at 7:01 PM, Alistair Bell <albell@shaw.ca> wrote:
> 
> And the pedant in you should have dope slapped me for typing pendant :-)
> 
> Hey, on another subject, since I installed an aftermarket tire pressure monitoring system, I’m so surprised at the apparent change in tire pressure with temp changes.
> 
> Yeah, of course it will change , but I never did the math using the old equations. Having this system, which include temp at the tire, shows me just how much the pressure changes with temp.
> 
> Been on the van since the summer, has worked prefectures except.. during the dark dark periods we have here during short days and rain, the little solar panel on the display can’t keep up .
> 
> Alistair