Jeep CJ/Scrambler 1971-1986 Repair Guide

Tires and Wheels

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See Figures 1, 2, 3 and 4

Inspect the tire treads for cuts, bruises and other damage. Check the air valves to be sure that they are tight. Replace any missing valve caps.

The tires should be checked frequently for proper air pressure. A chart in the glove compartment or on the driver's door pillar gives the recommended inflation pressure. Pressures can increase as much as 6 psi due to heat buildup. It is a good idea to have your own accurate gauge, and to check pressures weekly. Not all gauges on service station air pumps can be trusted.

Inspect tires for uneven wear that might indicate the need for front end alignment or tire rotation. Tires should be replaced when a tread wear indicator appears as a solid band across the tread.



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Fig. Fig. 1: There are tread wear indicators built into the tire. When they can bee seen the tire should be replaced



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Fig. Fig. 2: You could use a penny to check the tread depth. When Lincoln's head can be seen, the tire should be replaced



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Fig. Fig. 3: Tire rotation patterns



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Fig. Fig. 4: You can also check tire tread depth with an inexpensive gauge

When you buy new tires, give some thought to these points, especially if you are switching to larger tires or to another profile series (50, 60, 70, 78):

  1. All four tires should be the same. Four wheel drive requires that all tires be the same size, type, and tread pattern to provide even traction on loose surfaces, to prevent driveline bind when conventional part time four wheel drive is used, and to prevent excessive wear on the center differential with full time four wheel drive.
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  3. 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.
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  5. 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 makers furnish full measurement specifications. Speedometer drive gears are available from Jeep parts for correction.
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Dimensions of tires marked the same size may vary significantly, even among tires from the same maker.

  1. The spare tire should be usable, at least for low speed operation, with the new tires. You will probably have to remove the side mounted spare for clearance. This is especially true on 1972 and later models, since they have a wider tread and minimal tire-to-spare clearance.
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  3. There shouldn't be any body interference when loaded, on bumps, or in turning.
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The only sure way to avoid problems with these points is to stick to tire and wheel sizes available as factory options.

TIRE ROTATION



Tire rotation is recommended to obtain maximum tread wear. The pattern you use depends on personal preference, and whether or not you have a usable spare. Radial tires should not be cross-switched. They last longer if their direction of rotation is not changed. Truck type tires sometimes have directional tread indicated by arrows on the sidewalls. The arrow shows the direction of rotation. They will wear very rapidly if reversed. Studded snow tires will lose their studs if their rotation direction is reversed.

Mark the wheel position or direction of rotation on radial, or studded snow tires before removing them.

Avoid overtightening the lug nuts to prevent damage to the brake disc or drum. Alloy wheels can also be cracked by overtightening. Use of a torque wrench is highly recommended. Tighten the lug nuts in a criss-cross sequence shown to 85 ft. lbs.

TIRE USAGE



The tires on your truck 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 and 60 Series tires should be used only in pairs on the same axle; radial tires should be used only in sets of four.

Many states have vehicle height restrictions; some states prohibit the lifting of vehicles beyond their design limits.

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. Speedometer drive gears are available for correction.

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

The spare tire should be of the same size, construction and design as the tires on the vehicle. It's not a good idea to carry a spare of a different construction.

TIRE DESIGN



For maximum satisfaction, tires should be used in sets of five. Mixing or 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.

When radial tires 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.


WARNING
Radial tires should never be used on only the front axle!

 
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