This is sort of embarassing, but I will bite the bullet and ask:

Do you check air pressure in the tires when they are cold, warm or hot? This is for street use. My sensor went of in the car and I checked all the tires after the car has set in the garage for the night. They were all within about a 1 psi of each other at about 32 psi. I remember adjusting the tire preassure about a week ago and setting them all to 36 psi. This is on Good Year run flats after a 40 minute drive home in about 85F weather.

So my quesion is: should they be 36 psi hot, or cold?

Also, not sure why the sensor went of. All the tires seem close enogh to be spinning at about the same speed.

 

pls do pressure adjustment only when youre tires a cold

 

My 2005 MCS system seems to
detect one pound differences in the tires.
However, once balanced out, cold. No problems.
These are Pirelli run flat performance tires too.

 

Thanks for the answers. Refilled them to 35psi cold. Reset the pressure warning. Will see how it goes.

 

The system is not fool-proof. There are many false alarms. Bumps or uneven payment can cause it to go off. I've probably had mine go off a dozen times. Only once I had a flat. Actually the runflat tire actually blew. The runflat alert actually didn't go off until about 2 minutes later...

 

My sensors have never gone off (wondering if they work).

Always check the tires when you haven't driven the car. That why the reading is acurate and not effected by temperature.

 

On our '02, the light has been on once...when we had a screw in a tire and the pressure was down in the high 20's. I haven't had any problems with it going off even if a tire was down to 32 when I normally run 35.

 

Yep, that is the thing. Mine went off when I had a flat. Has not gone off sense. And last week when I checked the tires the left rear was actually about 10psi lower that the rest without a warning. And than yesterday the damn thing went off, but the tire pressure did not collaborate the warning. Go figure.

 

Check tire pressure cold. But "cold" doesn't mean standing in the sun in the afternoon for several hours and engine is "cold".

Direct sunlight will warm tires up quite a bit and affect tire pressure. Best to check them when all tires are shaded and your car is relatively cold. I check first thing in the morning or in the garage.

If your cold tires are about 33-44 psi then your warm tires can be about 38-39 psi. It depends on how warm they get.

The light comes on whenever I change tires and jack up one side which tilts the axles like a flat tire would or if I go over irregular road terrain and tip up one side as in a steep driveway. Just reset the light.

 

Tire pressures from manufacturers are stated based on 70 degree (in US) F.
10 degree change in ambient temp will increase or decrease pressure 1 lb.

So, if temp in garage is 60 F and you want 34 lbs in the tire make tire pressure 33 lbs. If its 80 F make the pressure 35 lbs. This, of course assumes that your tire temp. is the same a ambient, not having been driven for several hours and the tires are not setting in the sun.

 

Good info. Thanks for the tip.

 

You need to pump the tire pressure near the outdoor ambient temp
where you will be driving the car... (don't go just by the garage
ambient temp cause if you have a heated garage and temps outside
is -10F, you're going to have tires failing).

In the summer when I want to adjust tire pressure I pop the garage
door open for about 30min at night and run the large fans
inside the garage to circulate the air to rid most of the heat
from the cars engines.

After the garage is cooled off to about what is outside, I
close the garage door and just let the car sleep overnight. I check
the tire pressure in the morning.

 

I keep my factory 16" Dunlop SP5000 DSST tires inflated between 37-40 PSI cold. The ride is harsher but the steering feels sharper as well.

Anything below 35 PSI, is lame IMO.

 

Not sure I agree. While extreams could present a problem ie 90 in heated garage and -10 outside, I don't think a 6-8 lb span would "kill" a tire. Remember, even at -10 when you drive, it will warm the tire and pressure will increase. What if ambient in Maine is -10 and your driving to Fla. Do you stop in PA, VA, SC, GA and FL to keep letting air our of the tires? Then have to stop on the way back to add air.
Within reason, go by the ambient temp rule for setting pressure and you'll be OK.

 

Ive yet to measure tire pressures to go up in -10F weather, but
here's what ive found (205/50/16):

At 25F, pressure only went up 2psi on a sunny day.
At 15F, it only went up less than 1psi on a sunny day.

My target psi while warm (for street) is approx 39-40psi so in the
winter i use 37-38psi cold.

Summer psi goes up 4-5psi when warm so i usually use 34-35psi cold.

Just some reference numbers for anyone interested in setting warm
tires. :smile: