TPMS question
Thread Starter
Instructor
Joined: Jul 2016
Posts: 158
Likes: 9
TPMS question
Today the wife calls me and tells me the pressure on one of her tires was down to 24 psi. the other three were sitting at 26 psi. I had checked this past weekend and filled all to 30 psi. I brought the car home, waited 6 hours for tires to cool, and checked pressures. It's holding steady, so I don't believe I have a leak in that tire.
It was cooler out this morning, around 55. I know tires lose pressure in colder temps.
I checked in the manual and couldn't find an answer to this;
Does anyone know at what pressure the tpms sensors should trigger an alert in the DIC? 24 psi from the regular 30 is a 20% drop in pressure. I can't find an answer as to what pressure trigges an alert.
TIA.
It was cooler out this morning, around 55. I know tires lose pressure in colder temps.
I checked in the manual and couldn't find an answer to this;
Does anyone know at what pressure the tpms sensors should trigger an alert in the DIC? 24 psi from the regular 30 is a 20% drop in pressure. I can't find an answer as to what pressure trigges an alert.
TIA.
Drifting
Joined: Jul 2016
Posts: 1,481
Likes: 393
From: Virginia Beach Virginia
For whatever reason tire pressures seem to vary widely. Mine read 24 all around in the morning but were later all 28. Light has not come on (except the prior incident with the nail) even when at 24
Race Director
Joined: May 2008
Posts: 10,742
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From: Manheim Pennsylvania
For every five degree temperature change your tire pressure will either increase or decrease one psi. Under inflation is harder on the tire than over inflation (I have seen aircraft tires overheat and fail when under inflated). I just returned from flying into Churchill Canada. The temperature change was over sixty degrees. I had maintenance over service my tires seven pounds so that I would be operating at the minimum allowed tire pressure when I landed.
Moderator
Joined: Feb 2006
Posts: 38,882
Likes: 17,781
From: DFW Area TX
For every five degree temperature change your tire pressure will either increase or decrease one psi. Under inflation is harder on the tire than over inflation (I have seen aircraft tires overheat and fail when under inflated). I just returned from flying into Churchill Canada. The temperature change was over sixty degrees. I had maintenance over service my tires seven pounds so that I would be operating at the minimum allowed tire pressure when I landed.
From tirebuyer.com:
A good estimate to use when comparing tire pressure to air temperature is for every 10 degrees F, tire pressure will adjust by 1 psi. For example, if the outside air temperature increases 10 degrees, the tire pressure will increase by 1 psi.
Last edited by Zymurgy; Dec 9, 2016 at 12:25 AM.
Thread Starter
Instructor
Joined: Jul 2016
Posts: 158
Likes: 9
Checked pressure again this morning. Down to 24 again. All other tires at 30. Checked DIC, no message. I know tpms system is functional, onstar app shows correct current pressure for all 4 tires.
Pulled the tire and lo and behold, a screw in the treads. Second tire in in 6 months. So much junk in the roads around here. Glad I paid for the tire/wheel warranty. This will be the second tire they pay for, 2 more and I'm ahead of the game.
Pulled the tire and lo and behold, a screw in the treads. Second tire in in 6 months. So much junk in the roads around here. Glad I paid for the tire/wheel warranty. This will be the second tire they pay for, 2 more and I'm ahead of the game.
Last edited by Sandi587; Dec 9, 2016 at 05:08 PM.
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Generally speaking there is a 7 PSI gap allowed between recommended and when TPMS has to go off (could be part of the TREAD act which mandates TPMS). If a car is specified to 30 PSI the TPMS usually will go off at 23 and 37 PSI, also the TPMS will not go OFF until you cross the "hysteresis" threshold, usually 2 PSI (so if it sets at 23 it won't unset until it sees 25) this is to prevent "toggling" of the light on/off if you were near the limit for turning it on/off.