If you drive a car, you should know how to change a tire

If you don't know how to change a tire, isn't it time you learned? Don't wait until you're on a country road with no one to come to your rescue -- take an hour some afternoon to roll up your sleeves and learn how to fix a flat. Here's a quick course in tire changing.

Before you travel anywhere, make sure the trunk carries the required tire-changing tools, as well as some of the nice-to-have accessories that will make the job easier:

A fully inflated spare tire. Don't judge air pressure by sight or feel. Use an air-pressure gauge, which you can buy at an automotive store or perhaps borrow from your local service-station attendant. Check your owner's manual for the normal tire-inflation rate. Generally the tires should be inflated to between 24 and 28 pounds of air per square inch.

(Note: Some new cars are equipped with a type of ``temporary spare tire,'' which is lighter and smaller than the conventional spare. Some temporary spares come fully inflated, but others are stored ``deflated'' and should be inflated only when put into use. An air-pressure canister is supplied for this purpose. Check the owner's manual for the proper use of such temporary spares and how they should be inflated with the canister when needed.)

Proper-size wheel. Your tire should be mounted on a wheel that fits your car. You can tell by comparing tire-size designations marked on the sides of tires. Once the hubcap is removed, of course, you can compare the wheels visually.

Check the spacing between the lug nuts, as well as design similarities.

Air-pressure canister. Cars having special ``deflated temporary spares'' are equipped with a canister.

Shaped like a small fire extinguisher, it is used to inflate the spare tire once it is mounted on the car.

Conventional spares do not require the use of such a canister.

Lug wrench. Also called a tire iron, it is used to remove the lug nuts, which hold the wheels onto the car. One end of the wrench fits over the nuts to loosen or tighten them. The other end has a blunt tip, like a screwdriver, which is used to remove the hubcap.

Cross-shaft lug wrench. While you need the blunt end of a regular lug wrench, this special T-shaped wrench provides greater hands-on leverage for easier removal of lug nuts.

Bumper jack. While there are many kinds of jacks available to raise or lower a car, most automobiles come equipped with an upright jack that has these features: a jack hook that fits under the bumper or in a slot in the bumper; a metal tab that you adjust to raise or lower the car; and a small open-ended nozzle where you insert the blunt end of the lug wrench to pump the jack up and down.

Sturdy board. Conditions are not always ideal when you have to change a tire. A board approximately three-quarters of an inch thick and two feet square can be placed under the jack base to prevent the jack from sinking into soft ground.

High-powered flashlight. Some blowouts occur at night, too. A powerful, self-standing flashlight will help you see what you're doing, and it will also serve as an emergency light for oncoming traffic. Make sure it contains fresh batteries.

Old blanket and gloves. Use these items for protection as well as to stay clean. Gloves will protect your hands and knuckles from bumps and bruises, while the blanket will help to cushion your knees from hard, cold, and perhaps cindery surfaces.

With the instructor's guidance, go through the following tire-changing steps in your driveway:

1. Prepare the car for jacking. Apply the emergency brake and put the car in a safe holding gear: ``park'' for automatic transmissions and ``first gear'' for manuals. Turn off the ignition.

2. Remove the spare tire and tire-changing kit. Carefully lift the tire out of the trunk. If it's too heavy (some conventional spares weigh more than 40 pounds), try rolling it out to where it can be easily grasped and lowered to the ground. Remove all of the kit tools as well. Once the car is jacked up, it's difficult and dangerous to try to get something out of the trunk.

3. Brace the tires with blocks or bricks. This is an important safety precaution to keep the car from rolling when it is jacked up. If you're changing a front tire, blocks should be placed behind the rear tire diagonally opposite the tire being changed. If you're changing a rear tire, blocks should be placed securely around both front tires.

4. Remove the hubcap. Place the blunt tip of the lug wrench under the hubcap edge and apply pressure against the wheel. Do this in two or three places, so the cap pops off easily and undamaged. Lay the cap upside down, so you can put the lug nuts inside during Step 7. This will keep the nuts from rolling away or getting lost.

5. Loosen the lug nuts about two full turns each. You can try using the regular lug wrench, but you'll find that the cross-shaft wrench will give you more leverage and a better chance to loosen any stubborn nuts. If they're on too tight, have the instructor loosen them first. Penetrating oil will help to free nuts that are frozen or rusted to the studs.

6. Assemble the jack and raise the car. Position the jack in its base, place the jack hook on the bumper (underneath or in a pre-drilled slot), set the jack control tab for ``up,'' and insert the jack handle (blunt end of the lug wrench).

For safety, make sure the jack base is angled slightly under the car. As it is raised, the jack should become absolutely vertical. Now, using full up-and-down strokes, raise the car until the tire being changed is 1 or 2 inches off the ground.

7. Remove the lug nuts. With one hand holding the tire on, remove the pre-loosened nuts and place them in the overturned hubcap.

8. Remove the wheel. Grasp the tire with both hands and carefully pull it toward you. If you're crouched in a good position and braced for the weight, the tire should come off the studs and bounce to the ground safely.

9. Install the spare tire. Position the spare so that it can be raised and slipped on the studs in one gradual motion.

Have someone show you how first. A true expert can show you how to balance the fire on a lug wrench or foot so it can be raised more easily. Once the tire is on, screw the nuts on by hand; then tighten them with a lug wrench until the wheel turns. (Don't tighten them further until Step 11.)

10. Lower the jack. Flip the jack control tab to ``down'' and lower the car slowly.

11. Finish tightening the lug nuts. This should be done in a crisscross sequence, so the wheel is secured evenly on the hub.

12. Replace the hubcap. Tap it carefully in place with a rubber mallet or the palm of your hand.

13. Disassemble the jack.

14. Remove the wheel blocks.

15. Put everything back in the trunk of the car, including the wheel you just removed. Your instructor should show you how to grasp the wheel so you can lift it safely into the trunk.

16. Release the emergency brake.