Foosh

Agreed, given the numbers Zymurgy published above, the lower end of the warm range is actually cold, at least as far as the OEM PSS summer tires are concerned.

drs

I'm going to guess he is confusing the air pressure readout for temperatures.

ClydeFrog

You need to worry about it when the idiot (plenty of them) with cup2s on a 50 degree day thinks he has “warm” tires & is in oncoming traffic....

Foosh

Damned right. There was thread published about a week ago at a track outing showing a white C7 that piled into a tire wall on a cool morning, and I suspect that gauge was showing tires "warm."

Gearhead Jim

Thanks, I needed that.

Zymurgy

We've already discussed that the system does not actually measure the tire temperature. There are a lot of factors that would affect those temps. The ambient air temperature is only one factor. I imagine the ground is still much warmer than the ambient air temperature was. The tires are sitting on that warm ground getting warmed by it. I'm also guessing that you drove the car prior to parking it and that would have elevated the tire/wheel temperatures. The temperature sensor is inside the TPM sensor which is inside the tire. That a lot of mass to cool off and the air temperature (36) just isn't cold enough to offset the ground heat and existing tire wheel heat. How long was the air temp below 46 degrees? What was the air temp when you parked it? What were the tire temps when you parked it? How hot were your brakes? Just too many variables that we don't know.

I do know that the display does show Cold and others have posted it displaying Frozen.

Gearhead Jim

The factors you mentioned are all relevant, but...
On our C5 and C6, I would sometimes check the coolant, oil, and transmission temps, immediately after startup from overnight parking in our unheated garage; and then compare them with the two thermometers on the wall inside the garage. All of the temps would be identical within +/- 2'F.

I have a "laser" thermometer, I should compare the tire temps and air temps a few times during the winter and post the results here.
Somebody remind me if I forget to do it.

Groovepusher Sly

I always keep my display on the 4 wheel PSI. You can tell when your tires are warm, because when cold, the pressure is low. So if you air up to correct pressure when the tires are warm, if the car sits in the cold (below 32 degrees), when you start it the pressure will read low, 28-29 PSI. When the pressure comes up to 30 PSI your tires are warm.

Sly

speedlink

It reads the tire pressure per tire. Not the temp. As discussed in the other replies.

Gearhead Jim

Here are some readings with the laser thermometer taken in our unheated garage, with the car parked more than 24 hours. I take the temperature on the sidewall of the tire, right next to the TPMS sensor, the four wheels will be within +/- 2'F of each other:

10-26-2017
Tire temperature with laser thermometer 44'
Dash readout: "Warm"

11-06-2017
Tire temperature with laser thermometer 32'
Dash readout: "Warm"

11-08-2017
Tire Temperature with laser thermometer 28'
Car outside temp 34'
Dash readout: "Warm"

11-1--2017
Tire temperature with laser thermometer: 19
Dash readout: "Warm"

Since DanZR1 posted a similar experience, mine may be working as designed.
I wonder if there are different calibrations for the different models of C7 and their different tires? Ours is a 2017 Z51.

Foosh

No, both temp and pressure are read. See Zymurgy's chart. The problem is "warm" does not mean warm, and as others have demonstrated in this thread, it can actually mean you still have cold tires.

Gearhead Jim

I updated post #30 with my latest numbers, and included the outside air temp displayed by the car.

Gearhead Jim

Post # 30 just updated again.
I can't see how 19'F qualifies as "Warm" anywhere except in Antarctica.
It's actually below the temperature at which GM tells us not to move the car at all, or the summer tires may crack. I've got AS tires on the car now but neither the sensors nor the car computer knows that.

DanZR1

Jim, have you tried driving the car? I wonder if the sensors have to update, like the ambient air temp sensor does? FWIW, it didn't work for me in Dillon, but I had driven a bit before I rechecked, so in they they could have warmed up...

Gearhead Jim

I've wondered about that also, will test and report back some day.
Thanks for asking.

c54u

Some info here on tire temp categories.

Start video at 4:00

http://www.autoline.tv/daily/?p=29850&cpage=1

Gearhead Jim

A very good explanation, thanks.

But if my ABS/TC/AH think my tires are "Warm" when they are actually 19'F, that could lead to some nasty surprises.

Gearhead Jim

Problem Solved!

I noticed that our 2017 had occasional weird electrical glitches- showed me twice as "Driver #3" with no #3 fob, the tire temperature issue, the CTEK charger would sometimes temporarily lose its connection in the rear plug even though firmly plugged in, etc. Just the usual Corvette electrical problems, right? Hmmm...

Two days ago I took a guess and unplugged the Valentine "Savvy" unit from the OBD port. The Savvy powers the detector when the car is running and reads the car speed so it can mute warnings below whatever speed I set. It does not "tell" the car anything, it just "listens".

Voila!
Today I started the car at 37' temp, the tires said "Cold" but transitioned to Warm" after about 6 miles of driving. And the charger has been working properly for these two days.
Now, to find a better detector setup...

Thanks for all your comments.

DanZR1

Interesting, but doesn't explain mine reading Warm when I was in Colorado. (Un)fortunately, it seldom gets below 40 here for very long, and never in my garage. If I ever find myself parked overnight somewhere cold, I'll double check...

Gearhead Jim

You have my deepest sympathy.


Seriously, if yours ever acts up again, please post.

BTW, a local friend had intermittent TPMS problems with his C6 just because of a phone charger plugged in.