TPMS and Ambient Temperatures

I keep my tires at the placard pressures (30psi front, 33psi rear) at home where the ambient temperatures are in the 70s F (Ukiah, CA).

I visited my brother over the weekend (Bend Oregon) and when I left on Sunday morning the outside temp was 25 F. TPMS warning light was on and when I check the pressures it showed both fronts at 26psi and were yellow on the display.

You would think they would have incorporated an ambient reference so the stupid warning light doesn't come on when the outside temps are lower than normal. This is a linear relationship and easy to incorporate in the system. I would prefer a warning if the pressure is at least 5psi below placard or if pressure is going down at a rate that indicates a puncture.

It's a "crying wolf" sort of thing and makes me not trust the warnings as much.

Just ranting...

Dan

 

When the temps hit 40 a few weeks ago here in north Texas, the line at the Discount Tire free air check was 15-20 cars deep. "TMPS alert sir?" sez the guy.

"Auyp" sez I...;-)>

So it ain't just us Tundra pilots.

B

 

30 psi seems pretty low to me though I'm sure it rides nicely. I noticed a MPG difference (or at least thought I did) between 38 and 40psi.

 

I would keep an eye on tire wear with that low of pressure. I realize that's what Toyota "recommends" but I think it's for ride quality. I noticed better wear at 35psi all around.

 

I'm keeping an eye on it, so far so good. I'm close to 20k miles on my 2018 right now with recommended pressures.

Dan

 

On this last trip (900 miles RT) I got between 18-20mpg. This is including a few mountain passes and WFO passing on 97. 2WD, unladen, just me driving. I could still experiment with different pressures to see what effect it might have. On my 2006 I used to run 40psi all around (thinking it would be best for MPG) but had adverse tire wear. I dropped down to the placard 29 front, 32 rear and MPG did not change. Michelin tires.

Dan

 

An “ambient reference”? lolz to do what exactly?

unless the laws of thermodynamics have changed this season, the light came on because the pressure was too low.

 

The PSI will change 1 PSI per 10 degree temperature change either up or down. The pressure being low due to a temp change or other factor is irrelevant to the warning system doing its job.

 

So I'm supposed to get out and run the pressure up to 30psi in a 25F ambient, then let air out to 30psi when I'm back at 70F ambient? I would prefer an algorithm in the system to understand that 26psi will be measured at a 25F ambient and not trigger an alarm since everything is okay.

Dan

 

Yes, you are supposed to adjust the pressure. I wouldnt hold my breath on a "fix" that would prevent a safety feature from operating because a dynamic changed. Dangerous is dangerous no matter which way you slice it, and running tires low on air pressure is dangerous regardless of the temp increasing as soon as you get back to your area or not. For however many miles you drive in the lower temp. you are running the risk of your tires overheating due to underinflation and potentially suffering a blow out.

 

I'm pretty sure Discount Tire recommends 40 psi for my KO2's.

I'm getting great wear out of them. I'm at 55K and they still have some life in them, but it does sorta ride like a truck.

 

So how the hell did we survive before TPMS systems? I NEVER adjusted tire pressures due to ambient differences for decades including dozens of trips to the Tahoe area in the dead of winter and blazing hot drives through the desert during the heat of summer. I started out with the proper pressure and drove.

What I want the TPMS system to do is alert me if there is a leak that definitely would be unsafe. But again, I managed to drive safely to the side of the road if I was getting a flat and also during a complete blowout. I have been driving since 1961 and I'm still here to tell about it.

Dan

 

Now get off his lawn!!!!

..and come mow mine...;-)>

B

 

seriously??? did you attend 6th grade science class?

thermodynamics, all forms of energy. same ***t.

 

Okay, I give up, I'm done with this. Sorry to have wasted your time.

Dan

 

Sounds like it's working as it should.

 

I keep mine at 40psi, where I live temps range from -25f in winter to 85f in summer, I have never had a TPMS light come on.

 

I check my tire pressure at least once a month during summer and every 2 weeks or so during the "winter" months. Have done this since I started driving and I was always taught that it goes hand in hand with checking the oil and fluids. I normally run 3-5 PSI over anyway but with our temp swings in South Louisiana I tend to leave it adjusted at the lowest experienced temp.