Wednesday, November 19, 2008

New shoes for the car

When the time comes to buy the car a new set of shoes, style doesn’t matter very much.
Instead of looking for something in just the right color or the perfect heel, when you buy tires, you are looking for something that will perform like a sleek pair of running shoes and have the strength of a solid pair of hiking boots.
But if style is important – if raised white letters or a racy red stripe are gotta-haves – look for them after you have chosen a tire with the right tread and size for your vehicle.
The National Highway Transportation Safety Administration points out that good, well-maintained tires improve vehicle handling, protect you from breakdowns and avoidable accidents, and improve fuel economy.
Just like your shoes, the most important determinant of comfort and safety is size. Buy tires that are the same size as the ones that came on the vehicle when it was new. Unless you have changed the wheel size, your car was designed to wear specific tires.
Check the tire placard, usually located inside the edge or post of the driver’s door, the glovebox door or trunk lid, or your owner’s manual.
The tire size is a combination of letters and numbers, like P215/65R15. The “P” means it’s for passenger vehicles, the next three digits are width in millimeters from sidewall to sidewall. (The larger the number, the wider the tire.) The number after the slash is the aspect ratio, or the relationship of the height to the width. (A number of 70 or smaller indicates a tire with a short sidewall best suited for sharp handling on dry pavement.) The “R” means radial, which almost all tires are these days. The last two digits are the rim diameter in inches, or how big around your wheels are.
The other numbers that may or may not be on the side show the tire’s load index, or how much weight each tire can carry, maximum speed rating and whether the tire is rated for mud and snow use.
Also pay attention to the tread. Good tread keeps your tires from slipping on wet roads. It’s easy to spot a bald tire, but it’s much safer to change them before you get to that spot. Generally speaking, you should replace your tires when there’s just 1/16th of an inch of tread left.
One way to check is look for the tires’ tread-wear indicators. They are raised sections of rubber spaced in the grooves of the tread. When you see what looks like a stripe across the width of the tire, even with the outside of the tread, it’s time to change the tire.
Another way to check is with a penny. Hold the penny with Lincoln’s head upside down in the groove. If you can see the top of Lincoln’s head, it’s time for new tires.
And don’t be cheap. It’s usually best to replace all four tires at once. They all probably started wearing at once, and if you’ve taken good care of them, they probably are wearing down at the same rate. With a new set, you can be sure all your tires are the same quality and condition.
However, if the budget is too tight or you are replacing a newer tire that has gone flat, at least replace two tires. Have the tire store or garage put the new ones where they’re needed most – in front. Because you steer with the front wheels, they usually get the most wear. In addition, front-wheel-drive vehicles add all the force of traction up front. Take the two best remaining tires and put them on the back. And start saving now for replacing those tires. You’ll need to do it sooner then you think.
You can stretch the use you get out of a set of tires by practicing good tire maintenance.
The single most important thing you can do is keep your tires properly inflated. NHTSA says underinflated tires and overloaded vehicles are the primary causes of tire failure. That can mean more trouble than just a flat. A blowout at street speed can cause an accident or sent your vehicle into a roll.
You can find the information for both the correct inflation pressure and maximum load on the placard or in your owner’s manual. The tire pressure number printed on the side of the tire is NOT the one you should use. That’s the maximum pressure the tire can take. Pressure is measured in sounds per square inch, or psi.
Load is the lesser worry. Unless you regularly haul a trunkload of stones or pull a heavy trailer, you are most likely well within the load limits.
Inflation, however, is something you need to check regularly. Buy an inexpensive tire gauge at an auto parts or discount store and keep it in the car.
NHTSA says all tires can lose air over time, and with radial tires, it’s impossible to tell if the tire is underinflated just by looking at it.
Check your tires at least once a month, after the car has been sitting for at least three hours. When you drive, the friction between the tire and the road heats up the air inside, giving you a false, higher pressure reading.
Check the pressure with your gauge at the valve stem, the little nozzle toward the inside of the tire. Unscrew the cap and put the head of the gauge over the nozzle until you hear a short “pfft” sound. The gauge will show you how much pressure is in the tire.
If there’s too much, let a little air out of the tire with the help of your gauge. There’s usually a small knob on the head. Press it down on the small pin in the center of the nozzle. That releases some air. Recheck the pressure with your gauge.
Underinflation is more common than overinflation. If the tire doesn’t have enough pressure, go to the air pump at a nearby service station and add air.
Put the head of the pump on your capless nozzle and push until you hear a “pfft.” Many pumps automatically start pumping, while others may have a handle you have to squeeze. Check you pressure again with your gauge until the tire is about 1 psi over the recommended amount. (Remember, warm tires show higher pressure, and you had to drive to the service station.) Check the tires again when they are cold to see if you need to add more air.
While watching your tires’ pressure is important, it’s not the only care your tires need.
They also need to be rotated to maintain even wear. This is something best left to your service garage or tire store.
Check your owner’s manual for how frequently they should be rotated and the pattern of rotation. Usually, tires should be rotated about every 5,000 miles.
You also need to be sure your tires are properly aligned and balanced. Usually, this is checked when you take the car in for its periodic checkups, but if you feel vibration of shaking, get it in for an alignment and balance check.
Balancing wheels involves taking them off the car and placing them on a balancing wheel. If they are out of balance, a small lead weight is snapped on the rim to offset the heavy spot.
Alignment requires special machinery that can check the angle of the wheels on the vehicle’s frame and adjust it if it’s out of whack.
It usually takes some event to knock a wheel out of balance or alignment. Losing a lead weight will unbalance a wheel, and something as simple as driving hard over a curb or hitting a pothole can affect alignment.
If you do get a flat tire, it might be possible to repair it.
A hole in the tread from a nail, for example, can be plugged and patched. That involves taking the tire off the rim, inserting a plug in the hole and patching it on the inside.
If you get a hole in the sidewall, however, it’s time for a new tire. And remember, all tires wear down over time, so replace them in pairs. You wouldn’t wear one new shoe with one that’s been in your closet for a couple of seasons.

By Karl W. Ritzler
Originally posted on divinecaroline.com

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