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PV / T = k and where the run flats fall flat

Printed From: Puget Sound MINI Motoring Club
Category: Technical Discussions
Forum Name: Tires and Wheels
Forum Description: Post questions and comments about tires and wheels.
Printed Date: July/11/20 at 11:20am

Topic: PV / T = k and where the run flats fall flat
Posted By: Beakerzor
Subject: PV / T = k and where the run flats fall flat
Date Posted: September/07/14 at 8:39am
Susan and I are on an 2 week road trip deep into the Canadian Rockies with our new MINI.  Our first experience with Run-Flats.

We woke up in Jasper and the MINI saw its first frost.
Elevation  1,060m or 3,480 ft

Using the combined gas law, PV/T = k
as the (T)emperature dropped, with the (V)olume staying the same, and the (k)onstant not changing ever because of physics laws and what not, meant the (P)ressure had to drop with the temperature.

Basic physics 101 stuff.  It set off the "low tire" warning system, and sent us into a mini panic (pun intended).

Lessons we learned:
1. It takes a special machine to remove run-flat tires from a wheel, there are no such places near Jasper for hundreds of miles.  We would have had to buy new rims and tires, if we had a real flat.

2. The dash-board display system wouldn't tell us exactly which tire was low or by how much, it just said "tire(s) low".

I couldn't find any tire information using an OBD bluetooth device.  Is this even possible?  

TIP:  Always fix the tire pressure before leaving on a trip (which we did not).  Our repaired run-flat was at 41psi, and the other 3 tires were at 30psi.


Posted By: CORNERS
Date Posted: September/08/14 at 12:36am
OBD scanners won't talk to the tire pressure system. You'd need a special BMW/MINI software to do that. 


Kurt/04 R53" rel="nofollow - Check out My MOD MINI repair videos channel @ YouTube

Posted By: racingbmwm3
Date Posted: September/09/14 at 8:00am
Check all fluids and tire pressures before any trip and ideally at least once a month of regular driving.

'05 Cooper, BRG, Aerokit, Sport Package, 135k
'89 325iX, Diamondblack, 270k

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