by Tom Anderson
It may seem hard to believe, but arguably the most important parts on your vehicle in terms of efficiency, safety and performance are the tires. Even though the amount of each tire’s surface touching the ground at any given time is relatively tiny, those four contact patches, as they are known, have the final say when it comes to acceleration, braking and steering. As a result, it should go without saying that keeping those big rubber hoops in top form is a very big deal.
And keeping your car’s tires in optimum form starts with maintaining correct tire pres-sure. When checking tire pressures, it’s best to do so when the vehicle hasn’t been driven for at least a couple of hours.
The reason for this is that driving builds up heat in the tires, due to the rubber compressing under load during acceleration, braking, cornering and going over variations in terrain, and from the friction between the rubber and the road.
Thanks to hot air balloons, we know that hot air takes up more space, meaning it exerts more pressure on whatever vessel it’s contained in; thus, the warmer the tires, the more inflated (pardon the pun) the pressure read-out will be.
The actual act of checking the tire pressures is extremely simple: First, procure a quality tire pressure gauge. These gauges come in both analog and digital form, and work fine when used properly. Next, locate the valve-stem cap (the little hose thingy sticking out of the inside of the wheel rim) and unscrew the cap.
Now, couple the end of the tire pressure gauge onto the valve-stem and take the reading. Remove the gauge and the one-way valve will automatically close back up to keep any additional air from leaving the tire.
If the tire is low on air, take the air hose and couple it to the valve stem the same way you did with the gauge. Leave the air supply attached for a couple of seconds and then pull it off to check the new pressure. If it’s now too high, many tire-pres-sure gauges have a bleed valve that you can activate to gradually release whatever extra pres-sure there may be. If it’s still too low, re-insert the air supply and repeat the process until the correct pressure is reached. Finally, screw the valve-stem cap back on and repeat the whole process with the other three tires.
Of course, even if you check your tire pressures religiously (It’s a good idea to do so at least once a month.) the tires will eventually wear out. The best way to determine if it’s time to buy your ride some new shoes is to take a penny and hold it so Lincoln’s head is upside down and stick the penny in one of the grooves of the tread. If you can’t see any part of Lincoln’s head above his eyes, you can hold onto those tires a little longer. If you can see the top of Honest Abe’s head, it’s time to go tire shopping.
Also, with talk of $4-per-gal-lon gasoline growing louder by the day, fuel economy is becoming an increasingly big deal. One way to reduce the strain on your wallet is to make sure your tires are not under-inflated. An under-inflated tire has more trouble holding its round shape under the weight of the vehicle and the forces of lateral acceleration (cornering) and longitudinal acceleration (accelerating and braking). And since it takes less energy to spin something that’s really round instead of something that’s merely kinda round, your engine will use less fuel if you keep your tires at the pressure they should be.
Also note that over-inflated tires can cause blowouts (high pressure when parked gets really high when driving) and reduced vehicle control (smaller contact patches), and both under- and over-inflation cause uneven and premature tire wear.
In closing, your vehicle’s tires are responsible for so much of how your vehicle behaves that you’d be doing yourself and those around you a great dis-service by neglecting them. Or, to paraphrase the most over-used tagline in public service film history, take care of your tires, and they’ll take care of you.
