GM Caprice 1990-1993 Repair Guide

Tires and Wheels


See Figures 1, 2 and 3

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Fig. Fig. 1: A penny works as well as anything for checkingtire tread depth; when you can see the top ofLincoln's head, it's time for a new tire

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Fig. Fig. 2: Tread depth can be checked with an inexpensive gauge

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Fig. Fig. 3: Tread wear indicators will appear when the tire is worn out

The tires should be rotated as specified in the Maintenance Intervals Chart. Refer to the accompanying illustrations for the recommended rotation patterns.

The tires on your car should have built-in tread wear indicators, which appear as 1 / 2 in. (12.7mm) bands when the tread depth gets as low as 1/16 inch (1.6mm). When the indicators appear in 2 or more adjacent grooves, it's time for new tires.

For optimum tire life, you should keep the tires properly inflated, rotate them often and have the wheel alignment checked periodically.


See Figure 4

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Fig. Fig. 4: Recommended tire rotation procedure

Tire rotation is recommended at 7,500 miles and 15,000 miles thereafter, to obtain maximum tire wear. For all tire sizes, rotate the rear tires straight up to the front without crisscross and the front tires crisscross to the rear without dismounting the tires from the wheels. Torque wheel nuts as follows:

1990 Sedan - 81 ft. lbs. (110 Nm).
1990 Wagon and Police - 100 ft. lbs. (140 Nm).
1991 - 93 All Vehicles - 100 ft. lbs. (140 Nm).

Avoid overtightening the lug nuts to prevent damage to the brake disc or drum. Use of a torque wrench is highly recommended.


See Figure 5

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Fig. Fig. 5: Tire Performance Criteria (TPC) information location

When replacing your tires, you should take note of the Tire Performance Criteria Specification Number (TPC Spec. No.) molded into the tire sidewall near the tire size marking. The TPC Spec. No. shows that the tire meets rigid size and performance standards which were developed for your Caprice. When replacing your tires with all-season tread design, make sure your TPC Spec. No. has a MS (mud and snow) following the number.

If a replacement tire does not have a TPC Spec. No., you should use the same size, load range, speed rating and construction type (radial) as the original tires on your car. A different size or type of tire may affect such things as ride, handling, maximum speed capability, speedometer/odometer calibration, vehicle ground clearance, and tire or tire chain clearance to the body or chassis.

If the vehicle is equipped with an Anti-Lock Brake System (ABS), it is very important to have 4 tires of the same size and design, otherwise the ABS may not operate properly.

The tires on your car were selected to provide the best all around performance for normal operation when inflated as specified. Oversize tires will not increase the maximum carrying capacity of the vehicle, although they will provide an extra margin of tread life. Be sure to check overall height before using larger size tires which may cause interference with suspension components or wheel wells. When replacing conventional tire sizes with other tire size designations, be sure to check the manufacturer's recommendations. Interchangeability is not always possible because of differences in load ratings, tire dimensions, wheel well clearances, and rim size. Also due to differences in handling characteristics, 70 Series tires should be used only in pairs on the same axle; radial tires should be used only in sets of four.

The wheels must be the correct width for the tire. Tire dealers have charts of tire and rim compatibility. A mismatch can cause sloppy handling and rapid tread wear. The old rule of thumb is that the tread width should match the rim width (inside bead to inside bead) within an inch. For radial tires, the rim width should be 80% or less of the tire (not tread) width.

The height (mounted diameter) of the new tires can greatly change speedometer accuracy, engine speed at a given road speed, fuel mileage, acceleration, and ground clearance. Tire manufacturers furnish full measurement specifications.

Dimensions of tires marked the same size may vary significantly, even among tires from the same manufacturer.

The spare tire should be usable, at least for low speed operation, with the new tires.

For maximum satisfaction, tires should be used in sets of five. Mixing of different types (radial, bias-belted, fiberglass belted) should be avoided. Conventional bias tires are constructed so that the cords run bead-to-bead at an angle. Alternate plies run at an opposite angle. This type of construction gives rigidity to both tread and sidewall. Bias-belted tires are similar in construction to conventional bias ply tires. Belts run at an angle and also at a 90° angle to the bead, as in the radial tire. Tread life is improved considerably over the conventional bias tire. The radial tire differs in construction, but instead of the carcass plies running at an angle of 90° to each other, they run at an angle of 90° to the bead. This gives the tread a great deal of rigidity and the sidewall a great deal of flexibility and accounts for the characteristic bulge associated with radial tires.

Radial tire are recommended for use on all models. If they are used, tire sizes and wheel diameters should be selected to maintain ground clearance and tire load capacity equivalent to the minimum specified tire. Radial tires should always be used in sets of five, but in an emergency radial tires can be used with caution on the rear axle only. If this is done, both tires on the rear should be of radial design.

Radial tires should never be used on only the front axle.


Store the tires at the proper inflation pressure if they are mounted on wheels. Keep them in a cool dry place, laid on their sides. If the tires are stored in the garage or basement, do not let them stand on a concrete floor; set them on strips of wood.


The tire pressure is the most often ignored item of automotive maintenance. Gasoline mileage can drop as much as 0.8 percent for every 1 pound/square inch (psi) of under inflation.

Pressures should be checked before driving, since pressure can increase as much as 6 psi due to heat. It is a good idea to have an accurate gauge and to check pressures weekly. Not all gauges on service station air pumps are accurate.


A protective coating is applied to all aluminum wheels to prevent degradation. Avoid prolonged use of automatic car washes which will wear off the protective coating. When using cleaners, read the label on the package and make sure it will not damage or remove the protective coating.