Checking your tires is crucial in the summer. Long road trips with humongous loads and high temperatures can stress your Goodyears to the max. And, obviously, if the tires go, you go! Besides, no one likes to force a mother-in-law into changing a tire on the side of the road. (You want to save her dwindling strength for that big transmission job when you get home!)
2a. Tire Pressure
Make sure that you have the correct tire pressure in all five tires. (In case you never noticed, there's a tire in the trunk.) There's plenty of debate about what constitutes "correct" tire pressure, but we suggest going by what your vehicle manufacturer recommends, which should be listed on the side of the driver's door, on the glove compartment door, or in the owner's manual. Don't confuse the "maximum tire pressure" listed on the sidewall of the tire with the "recommended tire pressure" provided by the manufacturer of the vehicle. While it’s okay to inflate your tires to the "maximum tire pressure" number, "Recommended tire pressure" is the ideal pressure you want in your tires. If you're carrying an extra heavy load, follow the recommendation for "heavy loads," which is usually listed in the manual that came with your mother-in-law. (Or your car's owner manual.)
Ready for some more high-school physics? Remember that tire pressure will increase as the outside air temperature rises. In fact, tire pressure will go up approximately one pound for every 10 degrees Fahrenheit. So, tires that were at 35 PSI back in January when you drove to the slopes could easily be closing in on 45 pounds on a hot July day at the beach. Under some conditions that increase in pressure is enough to blow the tire! If nothing else, a tire that's overinflated will wear prematurely and will cause the car to handle and brake poorly. Don't count on your electronic tire pressure monitoring system to alert you to an overinflated tire, either — the warning light will only get illuminated when a tire’s air pressure is too low, not too high.
By the way, while you're out there checking the air in those tires, toss that stupid pencil-style pressure gauge in the dumpster where it belongs and get an accurate, dial-type gauge.
You also have to remember friction. As you drive, there's friction between the tires and the road. Friction means heat — and heat means an increase in tire pressure. So, here's what to do about your car's tire pressure: Check the tire pressure before you start driving. If the recommended pressure is 35 PSI, for example, it means 35 PSI before you start driving. If you check the tire pressure when you stop to get gas two hours later, it will be much higher than 35 PSI. If you check it at this point—after you've been driving--there is no way to know what the correct tire pressure should be. You'll be tempted to let air out of the tires, because the tire pressure will be greater than 35 PSI. Do not do this, because the tires will be under inflated.
2b. Tire Treadwear
Of course, you should always check the condition of your tires' treads. The minimum acceptable tread depth is 3/32 inch. This is about the distance from the edge of a penny to the top of Abe's head. But, if we were leaving on a trip, we wouldn't want the minimum tread. Because somewhere in the middle of that trip, you're going to be below the minimum tread So do you want to buy tires from the guy down the street, or from Uncle Luke's Gas Station and Charm School in the middle of the Bonneville Salt Flats? Why not take the trip on brand-new rubber?
While you're looking at the tire tread, keep an eye out for an uneven wear pattern. “Uneven” means the tire is more worn on one edge. This usually means you need a wheel alignment. Also, run your fingers along the tread and feel for lumps. The presence of lumps could mean that the tire is not balanced correctly. It could also mean that you were a cheapskate when you bought your tires. How do we know? Cheap tires deform more at high speeds. As a result, they can wear peculiarly. The end result can be lumps or other odd wear patterns.
Don't be cheap! This is no time to try to save a few bucks. If you're close to needing tires, get them now.