Okay here ya go from a previous posting (probably more than you wanted).


quote:
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Originally posted by barkley89
As expected, it got cold again. Surprise, light came back on. Went ahead and put 35-lbs all the way around and light went out. Starting to think maybe, just maybe...I had low tire pressure?! Before putting air all around, all five tires had 31-lbs. As tire pressure on door plate spec's suggest 32-lbs, I have hard time beleiving 1-lb would make a difference...but...

Other than a slightly harder ride, what would running higher pressure have for downsides?
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Could just be the spare throwing you off. You may want to try over-inflating it just a bit more, and let some of that air out if/when you need to use it. Although I have not mentioned it before, external atmospheric pressure can also affect internal tire pressure (rise and fall of barametric pressure), however is probably negligable compared to temperature changes.

I am not suggesting that anyone ride on over-inflated tires. Simply "over-inflate" them in a warm garage to compensate for much colder temperatures outside which will cause a drop in internal tire pressure. Perhaps the "best" thing to do would be to fill tires when they are sitting outside in the cold to recommended psi. But realize when you bring the car into warmer temperatures (say a heated garage), internal tire pressure will increase.

Once again from my previous thread:

It comes down to simple physics and the "ideal" gas law PV=nRT, or rearranged P=nRT/V. Where P is pressure, n=amount of air, R is a constant, T is temperature, V is tire volume.

Basically, the light goes on and off as pressure changes, and pressure increases as tire temperature increases. And pressure decreases as tire temperature decreases. The temperature change could be due to weather or friction from driving, or both.

The sensors only come on when tire pressure becomes too low (around 23 psi in my 4runner). Now, I live in Alaska, and my car can experience 100 degree temperature changes in a single day (from heated garage to artic cold).

My winter-time solution is this: In a 50 degree F garage, over-inflate tires by 5 psi-- light should be in good shape and stay off unless your tires get really cold (say -20 F or colder). Sometimes the light might come on when you first get in to drive, but after driving will usually go off due to tires being heated by friction. JUST REMEMBER TO LET SOME AIR OUT IN THE SPRING TIME, or your tires will be way-overinflated.

For summer conditions and 60-70 degree F garage temp, put tire at recommended psi.

I know the light can be a real nuisance for picky people like me, but it is there for a reason. If the pressure light comes on while you are driving, you probably are losing air--Unless you've gone from heated garage to much colder conditions.

When I get in my 4runner and it is outside and -35 deg F, I know my tire pressure light will be lit--so I walk around the vehicle and look at the tires before I get in and drive anywhere.

Good luck all