spicoli25

This morning when I went to the Garage and started the car to pull out, the tire pressure monitor told me that tire pressure was low in the front left and right rear tires. I looked at the tires and they looked fine. The car only has 2,500 miles on it and shouldnt have a tire problem. The weather dropped to around 50 degrees last night and was around 55 degrees this morning. I assumed that the tire pressure went down because of the cold. After driving for around 2 miles the warning lights turned off and I checked the tire pressure monitors and it said the tire pressure was 25psi. Has any other vette owners experienced this? Is this common?

vettenuts

These tires do not have a lot of air volume to start with, so if they are a little low it is not inconceivable that you will experience what happened. I have had several people in our club relate similar experiences.

MidLifeinMI

Same thing just happened yesterday - the tires (which in hot weather all start reading around 28PSI, then end up reading 32-33PSI hot) started off much lower in the colder (around 47F) weather; in fact, low enough to trip a message (think it has to be below 25 for a message to pop). Easy solution here: added 2-3PSI to each tire :) , since warm weather is just about gone for a while here. :cheers:

Oh, and BTW, you will NEVER be able to notice a low tire visually - you might not even be able to tell when one is flat, which is why you have the monitors in the 1st place. :yesnod:


[Modified by MidLifeinMI, 11:58 AM 10/8/2002]

Tomstoy

Normal. You should see how they react at temps below Zero.

Smoke-N-Shot

Nick

SoCal C5

Yes that is normal and i think there is a lesson to be learned. Temp. effects tire pressure on all cars but most people (at least those without a tire monitoring system) do not pay a bit of attention. Now put that together with the type problems that Firestone blamed on low tire pressure on the Explorers and you have a recipe for disaster. The lesson is check you tire pressure often and especially when there has been a significant change in weather/temp.

dm3557

I am by all means not a scientist, but I think it also has to do with the fact that when the tires (and the air inside the tires as well) get hot they create additional pressure, thus the higher tire pressure.

Most say the cold tire pressure is the true air pressure and the one to go by.

With run-flats it's very difficult to tell if you have a flat by sight. I was down to 14lbs of air because of a nail and the tire looked like the others.

B. Stewart

I had the same experience when my car was new, also. As others have stated, check the pressure often! :D

xilr8n

I had the same thing happen on our first cold day, a couple of weeks ago.

manual gauge and DIC both agreed to the #'s.

Just shows you have to rotate the air in the tires with the seasons :D

GraveDigger

I had the same thing happen only in reverse. Tire shop fixed leak in tire and filled to full. The first time I took it on the freeway and it heated and expanded the air, a warning came on the dash saying high tire preasure.


Tod :seeya

eaa1964

I have a 1999 and have similar situation. I have noticed that if my tire pressure drops below 30psi, the sensors do wacky things. I have confirmed this by manually checking the gauge against the sensors' reading. Another thing that happened to me was a sticky valve stem was creating a false positive reading on the sensor. Funny things about run flats...they look fine flat or low.

have a good one.

harleytim

I have been having the same problem with my 1999 coupe. The sensor alarm goes off, all four readings by the sensor says 25 psi and the actual reading with a gauge at the stem is 32.

What's up with that?
:confused:

Dave00C5

Mine does that when its really cold out to. Have to add air when the seasons change. :cool:

Oldvetter

When the tire pressure is less than 25 psi, the DIC will give you a low air pressure warning.

I think every 10 degrees F makes about a 2 psi difference in tire pressure.

Of course friction when driving also raises tire temperature/pressure. I found 2-4 psi in winter, 3-5 psi in summer.

chocoholic

For any gas, there are direct relationships between pressure, volume and temperature. (Boyle, Charles, Gay-Lussac, Avagadro, et al)

In this case it's a rule of thumb (if I recall) of about 1 PSI for every 10 degrees Fahrenheit change in the temperature of the air in the tyre.

Also, don't forget that with the runflat tyres having really stiff sidewalls that it's essential that you have a tyre pressure warning system and use a good tyre pressure gauge because a visual examination, as you have found out, is not going to give you much of anything.

harleytim

My issue is the difference in readings between an old fashion pressure gauge and the high tech GM pressure sensors. (i.e. 25 vs. 32)


[Modified by harleytim, 10:44 PM 10/20/2002]

Oldvetter

I use a digital gauge (+ - 0.5 psi) and my DIC is the same. Maybe your old fashioned gauge is off ?

chocoholic

Technically speaking, either your pressure gauge is crap (unlikely but possible) or your sensors are knackered. In your case it does seem odd for all four to be equally bad though so maybe a retrain using an el cheapo magnet might help?

FWIW, I also have one sensor that started off reading 2 PSI low and is now also giving frequent false error readings. As I have a laundry list of warranty repairs I will soon take the car into the dealer to have the whole lot attended to at once.

...A thought, if the pressure gauge you are referring to is the one on the end of the air-hose at the service station, then they are often really badly calibrated so all bets are off in those circumstances.


[Modified by chocoholic, 11:50 PM 10/20/2002]

TorchRed99Coupe

Same problem here in the Portland Oregon area. This time of year the temps can be quite low or still nice and warm. In the last few weeks they've been both. Whoever said their isn't much volume in those tires is right! From 25 to 30 psi is just a few seconds on the air hose. I'm running Bridgestone S03's (non run flats) so if I'm low, I should be able to see it. So far though I've only had one slow leaker from a nail which I'm sure I picked up from all the construction going on in the area. I just make sure I use an air guage I keep in the car so at least if I'm wrong on the pressure, it is always the same way!

Mark S.

I check mine every two weeks and keep 32PSI (cold) in them. If there's a change of 10 degrees in weather I'll recheck them. I have found that 32PSI works great (increases tread life, good ride, etc.) as opposed to the recommended 30PSI. My '94 C4 had 7/32 tread left on them at 23,000 miles (when I sold her after 7 years) and I'm convinced that watching my tire pressures on a regular basis made them last a lot longer.