We had a customer come in the other day complaining that their car was noisy when going over rough roads. We drove it and did the simple checks first. The front tires has 80 pounds of pressure in them! We let the excess air out and bingo, the noise was gone.
Checking air pressures is something we do everyday, and I am surprised at how often those pressures are off. Most people don't check their tire pressures, or if they do, are not sure how much to put in. Usually when we see a tire with real high pressures the customer added air because it "looked" low, so they pumped it up. This can be a dangerous situation because tires are designed to hold only so much air, go over that and you risk a tire blowout. On the opposite end a low tire will create excessive heat and either destroy the tire or cause it to shred. This has become less of an issue since the installation of TPMS sensors (Tire Pressure Monitoring System) on newer vehicles, but on older models there is no warning that your tire's pressures are off the mark.
Let me give you some tips on checking your tire pressures and knowing how much to put in.
First of all, I would suggest getting a tire pressure gauge and keep it in your glove box. You can pick one up at any autoparts store for a couple bucks.
Take a look at your tires when you know they have the proper pressure in them. You might notice they bulge a little where they contact the pavement, and you might even notice the fronts look flatter than the rears! This is normal because all passenger car tires are radials, a type of tire design, that will bulge a little on the bottom, and the fronts may look lower because that is were all the weight is from the engine and transmission. If you can remember how they look, you can use this as a reference for taking a look at them from time to time to see if they look low. A good time to do this would be when your putting gas in your car, it only takes a few
seconds. If you think one of your tires looks low, check it with your pressure gauge.
Every vehicle has it's own recommended tire pressure. The manufacture takes the weight of the vehicle, tire size, suspension package and a host of other things to determine what pressures to run in the tires. This pressure information will be posted on either the inside of the drivers or passengers door jamb, or in the glove box. I've even seen them listed under the center counsel lid as well but most vehicles are on the door jamb. These are the pressures you should run in your tires, and a lot of vehicles will have different pressure settings for front and rear. Do Not use the pressure listed on the tire itself. This figure is the maximum safe pressure for that particular tire brand and will always be higher than what your vehicle recommends.
The recommended tires pressures posted on your vehicle will say cold tire pressure, and this is the best way to check them. The air in your tires will expand when they get hot and the pressures will rise, so if you check them right after you get off the freeway and adjust them to recommended specs, they will drop a few pounds when the tires cool off. This is also why it's important to check them when the outside temps drop. It's not uncommon for us to see pressures down 10psi or more in the fall of the year when the temperatures get into the 30's or lower.
Correct tire pressures will make your tires last longer, give you better gas mileage, keep your vehicle handling properly and give you the best ride quality. With a little practice you should be able to detect and correct a low tire before it becomes a problem.