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Tires perform two important functions. First, they provide frictional contact between the wheels and the road so that good traction Is assured. This allows for rapid acceleration, offers resistance to the normal tendency of the car to skid on turns, and permits quick stops when the brakes are applied. Second, they provide a cushion between the road and the wheels to absorb the shock as bumps are encountered. Tires should not be taken for granted: check them regularly for proper inflation pressure, wear, and damage.
Without a doubt, neglect ruins more tires than anything else. For long tire life, riding comfort, and handling stability, keep your tires properly inflated.
Too little air pressure can result in excessive tire heat, abnormal wear, poor handling, and reduced fuel economy. An under-inflated tire will show maximum wear on the outside edges of the tire tread, with little or no wear in the center.
Too much air pressure can cause a poor ride and handling, as well as increased susceptibility to road impact damage. An over-inflated tire will show its wear in the center of the tread and little wear on the outside edges.
Making a Pressure Check
Tire pressure should be checked at least once a month (preferably more often) and always when the tires are cold. Cold tire ratings are applicable when a vehicle has been parked for 3 hours or more or driven less than a mile. Even a short drive can heat tip the tires sufficiently to defeat the purpose of the check. For this reason, it is a good idea to purchase your own pocket pressure gauge and carry it in the glove compartment, This type of gauge is generally more accurate than those found in service stations.
Make a pressure check as follows:
1. Look up the Inflation pressure recommended by the vehicle manufacturer. It is indicated either on a decal located in the glove compartment or on the left front vehicle door or in your owner's manual. However, keep in mind that the vehicle manufacturer normally specifies a pressure designed to provide a smooth ride at the expense of tire wear. Instead, you might want to use the pressure specified by the tire manufacturer, since it is geared toward maximum tire wear and performance. This recommended pressure can be found on the tire itself.
2. Remove the valve cap from the valve stem (assuming a valve cap is used).
3. Use a pressure gauge to check the pressure. Do not rely solely on the appearance of the tire; it can be deceiving. For example, while bias-belted tires look firm when they are inflated, radials tend to look a little on the soft side.
4. If necessary, add air. You might want to consider buying a small air compressor to do this job quickly and easily.
5. Reinstall the valve cap to prevent dirt and moisture from entering the valve core, which could cause leakage.
For sustained driving at highway speeds, cold inflation should be increased about 4 psi but should not exceed the following levels:
A change in tire pressure will occur with the onset of cold weather. Every 10-degree drop in temperature causes the pressure to decrease about 1 psi. Adjust the pressure accordingly, then bleed off the excess air when the weather gets warmer.
NOTE: Never bleed a hot tire. Bleeding only serves to increase the flexing action of the tire, which can result in damage or failure. When carrying heavier-than-normal loads, tire pressure should be increased-but never to an extent that is greater than the load range.
To equalize wear, most car and tire manufacturers recommend that the tires be rotated. Remember that front and rear tires perform different jobs and can wear differently, depending on driving habits and the type of vehicle. In a rear-wheel-drive vehicle, for instance, the front tires usually wear along the outer edges because of the scuffing and slippage encountered In cornering; the rear tires wear in the center because of acceleration thrusts. Bias-ply and bias-belted tires should be rotated about every 6,000 miles. Radial tires should be rotated at the first 7,500 and then at least every 15,000 miles thereafter. In the event of abnormal wear, find and correct the cause, then rotate the tires to promote more even wear. If the vehicle is equipped with a compact spare, do not include it in the rotation of the other four tires.
When installing snow tires, the regular tread tires on the rear should be moved to the front and the front tires stored. When the snows are removed, install the stored tires on the rear. Do not rotate studded tires; always remount them in their original positions.
NOTE: Snow tires installed on the rear require a 4 psi increase in the cold inflation pressure above that shown on the tire pressure decal, but should not exceed the maximum cold inflation pressure marked on the tire.
Tire rotation provides an excellent opportunity to check for potentially dangerous conditions. Abnormal or excessive wear can be caused by an incorrect wheel/tire imbalance or improper tire pressure.
Most tires today have built-in tread wear indicators to show when they need replacement. These indicators will appear as 1/2"-wide bands when the tread depth becomes 1/16". When the indicators appear in two or more adjacent grooves at three locations around the tire, or when cord or fabric is exposed, tire replacement is recommended.
If a tire does not have tread wear indicators, a tread depth gauge quickly shows in 32nds of an inch how much of a tire's tread is left. When only 2/32" is left, It is time to replace the tire.
When replacing tires, keep In mind the following tips from the Tire Industry Safety Council:
1. Tires should always be replaced with the same size designation or an approved option size as recommended by the auto or tire manufacturer. Use of any other size or type tire might seriously affect ride, handling, speedometer/odometer calibration, vehicle ground clearance, and tire clearance to the body and chassis.
2. When replacing original tires with an optional recommended size of different diameter, the speedometer must be recalibrated by installing the correct speedometer-driven gear.
3. To achieve the best all-around vehicle performance, bias-belted tires and bias tires should not be mixed on the same car.
4. Do not use radial tires with other types, such as bias or bias belted, except for short-term, low speed emergency use. Use only radial snow tires with radial-ply tires.
5. New tires should be Installed in pairs on the same axle. When replacing only one tire, it should be paired with the tire having the least wear, to equalize braking traction. Also, choose the same brand and model tire as the one It is being paired with; dissimilar tires can cause serious problems during panic braking.
6. When buying new tires, be sure the seller records your name, address, and tire identification number as required by federal law.
Before attempting to remove or replace a wheel when changing a flat tire or rotating tires, be sure to
1. Park the car on a level surface and set the parking brake.
2. Set the automatic transmission in PARK and block the tires so the vehicle does not roil.
3. If you are on a highway, activate the hazard warning flasher.
After removing the spare wheel and tire, jack, jack stand, and wrench from the trunk, proceed with changing the wheel as follows:
1, Remove the wheel cover. Keep in mind that some wheel covers are equipped with an antitheft locking system. The lock bolt for each wheel cover is located behind the hub ornament. A special key wrench is required to pry off the hub ornament and remove the lock bolt. In the event the key is misplaced, a master key set is available at the dealer.
2. Loosen, but do not remove, the hub lug nuts. In recent years more and more wheels are being equipped with antitheft wheel lugs (one per wheel). The key has a circular keyway that is matched to the female slot in the antitheft wheel lug nut. To loosen the antitheft wheel lug nut, inset the key into the slot, place the lug nut wrench on the key, and, while applying pressure on the key, loosen the lug nut.
3. Jack up the car as directed in the owner's manual, Always operate the jack with a slow, smooth motion. Raise the vehicle so the tire just clears the ground.
4. Remove all iu9 nuts or bolts and put them in the wheel cover. Take off the wheel.
5. Put the new wheel on and tighten the lug nuts or bolts slightly.
6. Lower the jack and tighten all the lug nuts or bolts securely using the recommended tightening sequence. If a torque wrench is available, tighten the lug nuts to the specified torque.
7. Check and adjust the air pressure in all the tires.
The most common tire repair problem is a puncture. When properly replaced, a punctured tire can be put back in service safely without fear of the leak recurring. Service punctures in the tread area only; never attempt to repair punctures in the tire shoulders or sidewalls. In addition, do not service a tire that has sustained the following damage:
NOTE: Tire sealants that are injected through the valve stem must not be used to service punctured tires because they can promote wheel rust and tire imbalance.
1. Inflate the tire to its maximum inflation pressure (marked on the tire).
2. Submerge the wheel/tire assembly in a tank of water, or sponge on a soapy water solution. The water or soapy solution will bubble at the exact spot of the leak.
3. Mark the location of the leak with a crayon so that it can be easily found once the tire is removed from the wheel.
4. Use a crayon to mark the valve stem location on the tire so that the original balance and runout can be maintained when the tire is remounted.
A tire should always be mounted or dismounted with a tire changer. This can be done at a service station. Once the tire is removed from the wheel and the cause of the puncture has been eliminated, the tire can be serviced from the inside using a combination plug and vulcanized patch. Although the service kit manufacturers instructions should always be heeded, following are some general recommendations.
CAUTION: Large holes (more than 1/8" In diameter) In radial tires should be patched Instead of plugged. Large plugs can damage the carcass of a radial tire.
1. After removing the cause of the puncture and reaming the damaged area, place a plug slightly larger than the size of the puncture in the eye of the insertion tool. Wet both the plug and insertion tool with vulcanizing fluid.
2. While holding and stretching the long end of the plug, insert it Into the puncture hole from inside the tire. The plug must extend above both the tread and inner liner surface, If the plug pops through, discard it and repeat the insertion procedure.
3. Once the insertion tool has been removed, trim off the plug 1/32" above the inner liner surface. Do not pull on the plug while cutting.
NOTE: Dismounting the tire from the rim is not always necessary when plugging a tire, It the source of the leak is obvious, the repair can be done from the outside of the tire; in many cases the wheel doesn't even have to be removed.
1. After buffing and cleaning the tire, carefully remove the backing from the patch.
2. Spread vulcanizing fluid over the punctured area and let it dry.
3. Center the patch over the puncture.
4. Run a stitching tool over the patch to help bind it to the tire.
NOTE: When repairing radial tires, only a specially approved radial patch should be used. These patches have arrows that must be lined up parallel to the radial plies.
This is very similar to a cold patch. The only difference is that the hot patch is clamped over the puncture and heat is applied to make it adhere.