Emergency need tire pressure advice!

[Dirk Diggler]

Hi fellas. Strange occurance with my girl's 2017 G4's tires. So last Friday I had to take the G4 into a Firestone tire shop because my girl noticed her tpms light going on on her drive to work. It didnt flash, indicating a tire sensor issue, it just came on, indicating a tire pressure issue. She drove back home after work, on the highway, and the tpms light went out. When she got home, I measured her psi. The front two and the back driver's side tires were all at 33 psi. The back passenger's side however was at 27 psi! I immediately took it too the tire shop to see if the back right tire had a slow leak. They checked it, said there was no leak and that the tire looked fine. They also put 35 psi in all 4 tires, the tpms sensor went out and all was fine, until today.

My girl just told me her tpms light came on when she turned on her car after work and then went out on the highway. I just measured her tires again and the complete opposite! The back right tire is at the correct 35 psi and all the others are at 30 psi! What in the world could be going on?

[Mark]

It could simply be the result of cold mornings & lower psi. Warmer afternoons the tire pressure is ok. Some tire gauges aren't accurate either.

I would put 40 pounds in them & see what happens for a week or two. Just pump them up yourself at a gas station.

[Dirk Diggler]

We have had a couple of cool nights the past couple of days, highs in 80s lows in 50s. That sensor is just supposed to go off if a tire gets below 27 psi though. Why is it triggering when none of the tires got below 33 psi? My measure gauge is solid, I believe, it matched up perfectly after I got back from the tire shop the first time, I tested it.

[Mark]

We have had a couple of cool nights the past couple of days, highs in 80s lows in 50s. That sensor is just supposed to go off if a tire gets below 27 psi though. Why is it triggering when none of the tires got below 33 psi? My measure gauge is solid, I believe, it matched up perfectly after I got back from the tire shop the first time, I tested it.

30 psi in the afternoon could be less in the cool morning, & that could set off the light. Put 40 psi in all four tires. I run my tires 40-42 psi all year.

[Dirk Diggler]

Thank you Mark

[Dirk Diggler]

I put 30 psi in all 4 just now. Going to monitor the situation.

[Eggman]

Doesn't the TPMS also signal a pressure loss of a certain amount? This is different from a fixed pressure of say 27 psi. I'm talking about losing say 5 psi (random number picked for this example.) Isn't that used to trigger sensor registration?

[Top_Fuel]

Put 40 psi in all four tires.

I put 30 psi in all 4 just now.

Hey Dirk...I assume you meant to say 40 like Mark suggested?!?


If you have a tire that shows 30 PSI at normal daytime temperatures right now in Atlanta, it could easily drop 3-4 PSI during overnight temps...which puts you into the TPMS warning range of less than 27 PSI.

Other factors that you may want to keep in mind...

• If you are checking the tires in the middle of the day when it's warm, they will be at their highest PSI.
• If you are checking the tires right after the car has been driven, they will also be at their highest PSI (tires get warmer when driven).
• If you are checking tires after they've been sitting in direct sunlight for a while, they will be at a higher PSI. Direct sunlight hitting a black tire makes them warmer.
• TPMS sensors aren't 100% accurate. You could have one that is off by 1-2 PSI.
• Your air pressure gauge may be a piece of junk. If it's a $0.99 stick-type, it's probably not super-accurate.
• Don't rely on the air pressure gauge of a gas station air pump or other inflation device. Use a quality pressure gauge.

[Top_Fuel]

Doesn't the TPMS also signal a pressure loss of a certain amount?

If a TPMS sensor detects a rapid pressure loss (something like a 3 PSI pressure loss in less than 30 seconds) then the sensor will immediately transmit its pressure data. This is one way that some people "trigger" a TPMS sensor during sensor registration.

If you have a tire that is quickly going flat while driving, the TPMS light will come on more quickly because the sensor is broadcasting more frequently. Otherwise, a sensor is only sending data out once every minute or so while cruising down the highway.

[Johnny Mullet]

I been running 40 in my stock tire/wheel combo and my aftermarket set.