SECTION 10

WHEELS AND TIRES

CONTENTS OF THIS SECTION

Figure Index
Wheels and Tires
Troubles and Remedies
Assembly Manual

Figure Index

Index

All passenger car models carry short spoke disc type wheels with tubeless type tires. The wheels are connected to the front wheel hubs and rear axle shaft flanges by five studs and nuts each. Series 1500 and 2100 vehicles have a 10 11/16" diameter snap-on type hub cap made of stainless steel. The 2400 series models carry stainless steel wheel discs, 15 1/8" in diameter.

The tires used on all models are of the 6.70-15 size with a 4 ply rating. The tubeless tires are simply a tire casing of a cross section similar to tube-type tires with an impervious inner layer to retain the air inside the tire. A snap-in type air valve is assembled to the rim. This type of tire normally will not leak air from a puncture as long as the puncturing object remains in the tire.

The service operations are basically similar to established practices in tube-type tires. The spare tire is mounted vertically in the trunk compartment on all models except station wagon and sedan delivery. These models carry the spare tire horizontally in a covered well in the rear body floor. A bumper-type jack with a wide base, and a combination jack handle, wheel nut wrench and hub cap remover are supplied with all models.

Care and Maintenance

Testing Tire Pressures

The correct tire pressure for all models is 24 pounds front and rear. Frequent checking is essential with low pressure tires as variations of only a few pounds make an appreciable difference in riding qualities, handling ease and tire wear. It should also be general practice to check tire pressures each time a car is brought in for service, not only as a convenience to the owner, but also to reduce the possibility of owner complaint of riding, steering or tire wear due solely to improper tire inflation. Checking inflation pressures should be a part of every lubrication job.

The following recommended pressures must be maintained to obtain maximum tire performance.

Starting Pressure - 24 lbs. when car has been standing three hours or driven less than a mile.

City Pressure - 27 lbs. after driving car three miles or more below 40 miles per hour.

Highway Pressure - 29 lbs. after driving car three miles or more above 40 miles per hour.

Hard driving normally increases tire pressures. Do not "bleed" tires to reduce this higher pressure.

When checking tires, servicemen should be careful to reinstall valve stem caps. These caps provide an essential function in keeping dirt out of the valve and in reducing the possibility of slow leaks through the valve.

PUNCTURE INSPECTION

Every 1000 miles or at each lubrication, the tires should be inspected for puncturing objects. If such are found, they should be removed and the tire repaired as explained in this section.

CHANGING ROAD WHEELS

To change the road wheels using the jack that comes with the car, observe the following procedure.

1. Set hand brake and block front wheels if rear wheel is being changed.
2. Remove hub cap or wheel disc and break . wheel mounting nuts loose.
3. Place jack directly under bumper just outside bumper guard and raise car until wheel clears ground.
4. Remove wheel mounting nuts and remove wheel from hub or drum.
5. To replace road wheel, reverse the above instructions. Proper torque on nuts is 45-65 ft. lbs. CAUTION: On models equipped with discs, index locating lugs with notches in rims.

INTERCHANGING TIRES

Normal tire wear is uneven between the front and rear wheels because of the difference in the functions of the front and rear tires. To minimize tire wear and tire noise, it is recommended that tires be interchanged both as to front or rear use and as to change of direction at intervals of from 4,000 to 5,000 miles.

In addition, utilizing the spare tire in rotation with the other four tires gives 20% more total car mileage before replacement tires must be purchased.

The recommended plan for interchanging tires is based on the following steps.

Move the left front wheel to left rear, left rear to right front, right front to spare, spare to right rear and right rear to left front.

In detail, the plan provides the changes as shown in Figure 1 each time the tires are interchanged.

CLEANING WHITEWALL TIRES

A great deal of ordinary road dirt which collects on white sidewall tires may be sponged off with clear water or a mild soap solution.

Chevrolet Whitewall Tire Cleaner, however, is a quicker and more effective cleaner for removing dirt and stains from whitewall tires and in many cases it will remove stains and discoloration that the simpler method of soap and water will not remove.

Under no circumstances should gasoline, kerosene or any cleaning fluid containing a solvent derived from oil be used to clean whitewall tires. Oil in any form is detrimental to rubber and a cleaner with an oil base will discolor or injure whitewall tires.

Service Operations

Correction of Irregular Tire Wear

Heel and Toe Wear - This is a saw-toothed effect where one end of each tread block is worn more than the other.

The end that wears is the one that first grips the road when the brakes are applied.

Heel and toe wear is less noticeable on rear tires than on front tires, because the propelling action of the rear wheels creates a force which tends to wear the opposite end of the tread blocks. The two forces, propelling and braking, make for more even wear of the rear tires, whereas only the breaking forces act on the front wheels, and the saw-tooth effect is more noticeable.

A certain amount of heel and toe wear is normal. Excessive wear is usually due to high speed driving and excessive use of brakes. The best remedy, in addition to cautioning the owner on his driving habits, is to interchange tires regularly.

Side Wear - This may be caused by incorrect wheel camber, underinflation, high cambered roads or by taking corners at too high a rate of speed.

The first two causes are the most common. Camber wear can be readily identified because it occurs only on one side of the treads, whereas underinflation causes wear on both sides. Camber wear requires correction of the camber first and then interchanging tires.

There is, of course, no correction for high cambered roads. Cornering wear is discussed further on.

Misalignment Wear - This is wear due to excessive toe-in or toe-out. In either case, tires will revolve with a side motion and scrape the tread rubber off. If misalignment is severe, the rubber will be scraped off of both tires; if slight, only one will be affected.

The scraping action against the face of the tire causes a small feather edge of rubber to appear on one side of the tread and this feather edge is certain indication of misalignment. The remedy is readjusting toe-in within 1/16" to 3/32" inch, or rechecking the entire front end alignment if necessary.

Uneven Wear - Uneven or spotty wear is due to such irregularities as unequal caster or camber, bent front suspension parts, out-of-balance wheels, brake drums out-of-round, brakes out-of-adjustment or other mechanical conditions. The remedy in each case consists of locating the mechanical defect and correcting it.

Cornering Wear - Since the introduction of independently sprung front wheels, improvements in spring suspension have enabled drivers to negotiate curves at higher rates of speed with the same feeling of security that they had with the older cars at lower speeds. Consequently, curves are being taken at higher speeds with the result that a type of tire wear called "Cornering Wear," frequently appears.

When a car makes an extremely fast turn, the weight is shifted from an even loading on all four wheels to an abnormal load on the tires on the outside of the curve and a very light load on the inside tires, due to centrifugal force. This unequal loading may have two unfavorable results.

First, the rear tire on the inside of the curve may be relieved of so much load that it is no longer geared to the road and it slips, grinding off the tread on the inside half of the tire at an excessive rate. This type of tire shows much the same appearance of tread wear as tire wear caused by negative camber.

Second, the transfer of weight may also overload the outside tires so much that they are laterally distorted resulting in excessive wear on the outside half of the tire, producing a type of wear like that caused by excessive positive camber.

Cornering wear can be most easily distinguished from abnormal camber wear by the rounding of the outside shoulder or edge of the tire and by the roughening of the tread surface which denotes abrasion.

Cornering wear often produces a fin or raised portion along the inside edge of each row in the It tread pattern. In some cases this fin is almost as pronounced as a toe-in fin, and in others, it tapers into a row of tread blocks to such an extent that the tire hits a definite step wear appearance.

The only remedy for cornering wear is proper instruction of owners. They should be shown that rubber is being ground off of their tires and they should be instructed to drive a little more slowly on curves and turns. Also, the tires should be interchanged at regular intervals.

Dismounting and Mounting Tires

The rims used on all passenger cars are of the familiar drop center design. Dismounting tubeless tires presents no problems if the correct procedures are used and the following precautions observed.

1. Remove the valve cap and valve core. Let out all the air.
2. Press one side of the tire into the rim well. Use bead loosening tool or if regular tire irons are used, take particular care not to injure or tear the sealing ribs on the bead. CAUTION: Never use tire irons with sharp edges.
3. Using tire irons on the opposite side, remove bead, taking small "bites" around the rim.
4. Turn the tire over, and use two tire irons, one between the rim flange and the bead to pry the rim upward, the other iron to pry outward between the bead seat and bead.

When mounting a tire on a rim.

1. Coat the inside and outside of the bead with a tire mounting compound. This will make the work much easier. Do not use oil or grease.
2. When installing the tire, make certain that the balancing mark on the tire is in line with the valve stem. Otherwise the assembly will be unbalanced.
3. Mount the first bead in the usual manner. Use tire irons only, never a hammer and carefully work bead into center of rim, taking small "bites" with irons. CAUTION: Do not use a hammer.
4. Install other bead in similar manner.
5. Install valve core.
6. Inflate the tire. Hold the tire and wheel assembly in a vertical position and bounce on floor at various points around its circumference to snap beads out against the rim flange. This will provide partial seal to start inflation. Inflate the tire with quick "shots" of air to 40 pounds to firmly seat the sealing beads. Reduce tire pressure to 24 pounds. NOTE: If a seal cannot be effected in the foregoing manner with the rush of air it can be accomplished by applying to the circumference of the tire a tire mounting bond or heavy sash cord and tightening with the use of a tire iron. On tire mounting machines, bouncing the tire assembly is not required. The tire should be lifted on the rim to force the top tire bead against the top rim flange. The weight of the tire will seat the bottom bead.

Small holes (UP to 1/16") in tubeless tire may be repaired without removing the tire or wheel from the vehicle. Larger holes or rim defects require wheel and tire removal and disassembly for proper correction. Size of puncture can usually be ascertained by the puncturing object.

Small Hole Repair

1. Jack up the car so that the wheel revolves.
2. Do not remove the tire from the wheel.
3. Inflate tire to operating pressure-24 lbs.
4. Wipe the tread clean and inspect carefully by applying water to the tread and slowly revolving the wheel.
5. Mark around the place or places where the bubbles appear, and then reduce pressure to 5 lbs.
6. Wipe tire dry.
7. Clean injury with hand rasp, removing all foreign matter. Dip rasp in solvent and thoroughly clean injury.
8. Remove plug from special sealing gun nozzle, turn handle of gun slightly until sealing dough appears. Then wipe it off to make sure that material is fresh at the nozzle end.
9. Center gun nozzle over puncture and press firmly against hole and turn handle. Turn handle 1 1/2 to 2 full turns to fill hole with puncture-sealing dough (fig. 2).
10. Replace plug in nozzle of pressure gun.
11. Allow tire to stand 15 minutes before reinflating to operating pressure.

Injuries up to 3/16" diameter

There are three methods of repairing injuries up to 3/16"' diameter, hot patch, plug and cold patch. As on tube-type tires, the hot patch method usually gives the best results.

1. Inflate tire to recommended operating pressure.
2. Wipe the tread clean and inspect carefully by applying water to the tread and slowly revolving the wheel. Mark around the place or places where bubbles appear.
3. Remove tire and wheel assembly from car.
4. Demount tire. Clean out injury with hand rasp.

Hot Patch Method

1. Fill injury from outside of tire, using a resealing gun as used on small injuries.
2. Clean injury area on inside of tire with a solvent and allow to dry.
3. Roughen area around injury.
4. Center hot patch over injury and clamp with special hot patch clamp tightened finger tight (fig. 3).
5. Ignite patch. Allow 15 minutes to cool. Remove metal cup and blow out ashes.

Plug Method

1. Clean an area of 3 in. in diameter around injury on inside of tire by light rasping or buffing. Wash, using solvent sparingly and apply Rubber Cement. Allow to dry.
2. Prepare plug by wire brushing or rasping flat side. Apply cement on under side of mushroom only and allow to dry.
3. Dip the wire plug installation needle in cement and push through hole from inside. Then apply cement to the stem of plug as a lubricant, and pull through hole while cement is still wet. Pull plug into place with steady continuous pull (fig. 4). Do not stop, or jerk. When plug is firmly seated against the inside of tire, use stitcher to remove all air pockets.
4. Trim plug slightly above flush of tread surface. CAUTION: Do not stretch plug while cutting.

Cold Patch Method

1. Fill injury from outside of tire, using a resealing gun. (Replace nail in gun nozzle after using).
2. Thoroughly clean inside of tire around injury with solvent. Allow to dry.
3. Roughen area around injury with hand buffer or wire brush.
4. Cement area around injury. Allow to dry. Apply Cold Patch and stitch down (fig. 5).
5. Remount tire. Inflate to 40 pounds and recheck in a water tank for leaks. Reduce pressure to normal 24 pounds.

Injuries Over 3/16" Diameter

Repair of injuries over 3/16" diameter should be accomplished with a vulcanizing process, similar to repairs on tube-type tire casings.

Rim Repair

1. Straighten the rim if it is bent or dented.
2. Clean rim flange thoroughly with small piece of steel wool or sand paper.
3. Inspect the butt-weld in the rim flange area to make certain there is no groove or high spot. Any grooves or high spots must be filed flat and smooth.
4. On riveted rims, loose rivets can be tightened by peening the rivet head with a ball peen hammer while being backed up with hammer from other side. Do not braze or weld loose rivets (fig. 6).
5. If air loss occurs at valve it can be corrected by replacing valve core or valve assembly.

Valve Assembly-Replace

1. Cut or drive old valve assembly out of rim.
2. Clean valve hole and surrounding area on inside of flange with steel wool.
3. Coat O.D. of new valve assembly liberally with tire mounting compound (fig. 7).
4. Insert assembly through rim from inside. Snap into place, using a pair of slip-joint pliers with one jaw on rim and one jaw on base of valve assembly.

A wheel and tire assembly may lose its original balance due to irregular tire wear, tire repair or some type of misalignment. Consequently, if front end instability develops, the tire and wheel assembly should be checked for static and, in severe cases, dynamic balance. The assembly should also be checked for balance whenever any original tire is replaced or repaired, and especially in cases where nonstandard tire equipment, such as an extra ply casing, is used.

Static Balance (still balance) is the equal distribution of weight of the wheel and tire assembly about the axis of rotation so that the assembly has no tendency to rotate by itself. Static unbalance causes the pounding action of the front wheels that is called "tramp."

To correct static unbalance:

1. Remove wheel and hub from spindle as a unit.
2. Clean all grease from wheel bearings and races.
3. Clamp a clean spindle in a bench vise, or if the spindle on the car must be used, clean it carefully.
4. Mount the wheel on the spindle and adjust the bearings loosely so that the wheel is just held in position and is practically frictionless.
5. Make sure that the tire is inflated to the correct pressure.
6. Start the wheel in motion and allow it to stop by itself. When it stops, the heavy side will be at the bottom.
7. Mark the heaviest point and also the uppermost or lightest point.
8. Install two balancing weights on the rim opposite each other and 180 away from the heavy point.
9. Move these weights equally in opposite direction toward the heavy side until the wheel is in balance.
10. Repack wheel bearings, reinstall and adjust bearings as explained in Section 3, "Front Wheel Bearings-Adjust."

Dynamic Balance (running balance) requires not only that the wheel be in static balance, but also that it runs smoothly at all speeds on an axis which runs through the center line of the wheel and tire and is perpendicular to the axis of rotation. Dynamic unbalance sets up forces which cause the wheels to wobble or "shimmy."

The quickest and best methods of testing and correcting dynamic unbalance are by the use of dynamic wheel balancers which are available commercially. These commercial balancers include all necessary instructions on where and how the balancing weights should be placed. The following information, however, will help in the correction of dynamic balance.

When a wheel that is statically unbalanced is dynamically in balance, the dynamic balance can be retained while correcting the static balance by installing the corrective weights so that half of the weight required is placed on the inner edge of the rim and the other half on the outer edge of the rim.

Dynamic unbalance can be corrected without destroying static balance by installing weights so half of weight required for dynamic balance is placed on the rim opposite the heavy point, while the other half is placed 180° away and on the opposite side of the rim.

Wheel Run-Out and Eccentricity

The wheels should not run out (wobble) more than 1/16" as measured on the side of the rim at the base of the tire. Excessive run-out is the result of a bent wheel, an improperly mounted wheel, worn knuckle bearings or steering connections. These parts should be checked for correct adjustment, proper alignment and wear whenever excessive run-out is encountered. The wheels should also run concentric with the steering knuckle spindle within 1/16 inch as measured on the tire bead seat of the rim with the tire removed. Wheel run-out, eccentricity and balance are closely associated with steering and front wheel alignment. Further information on these subjects will be found under "Front Suspension."

TESTING FOR TIRE NOISE

Noise caused by the normal action of tire treads on various road surfaces is often confused with rear axle gears or other noises in the car.

The determination of whether tires are causing the noise complained of is relatively simple. The car should be driven at various speeds and note taken of part throttle, sudden acceleration and deceleration as axle and exhaust noises show definite variations under these conditions, while tire noise will remain constant. Tire noise is, however, most pronounced at speeds of approximately twenty or thirty miles per hour.

The tires may be further checked by driving the car over smooth pavement with the tires at normal pressure and again over the same stretch of pavement when the tires have been inflated to fifty pounds pressure. Reduce the tires to normal pressure (24 pounds) one at a time to determine faulty tire or tires. This high inflation pressure should immediately be reduced to normal after test. If the noise for which the test is being made is caused by tires, it will noticeably decrease when the tire pressure is increased, whereas axle noise should show no change in volume.

If, on inspection, the tires on the front wheels are found to be creating most of the noise, the alignment of the front wheels should be checked, as excessive tire noise usually results from low tire pressure, incorrect alignment or from uneven tire wear.

Troubles and Remedies

WHEELS AND TIRES

Symptom and Probable Cause
Probable Remedy

Front Wheel Shimmy

a. Loose wheel lugs.
a. Tighten lugs.

b. Loose or broken wheel bearing.
b. Tighten or replace bearing and adjust according to instructions.

c. Bent wheel.
c. Replace or straighten wheel.

d. Improper alignment.
d. Front end alignment as per specifications.

e. Wheel out-of-balance.
e. Balance wheel.

f. Loose tie rod ends.
f. Replace tie rod ends.


Hard Steering

a. Low air pressure in tires.
a. Inflate tires to recommended pressure.

b. Lack of Lubrication.
b. Lubricate according to instructions.

c. Improper wheel alignment.
c. Front alignment correction.

d. Sagging front or rear spring.
d. Replace springs as required.

e. Bent wheel or spindle.
e. Straighten or replace wheel or replace spindle.

f. Broken wheel bearings.
f. Replace necessary bearings.

Improper Tire Wear

a. Improper air pressures.
a. Inflate tires to recommended pressure.

b. Not rotating tires as recommended.
b. Rotate tires according to instructions.

c. Improper acting brakes.
c. Correct brakes as required.

d. Improper alignment.
d. Align front end as per specifications.

e. High speed driving on turns.
e. Take turns more slowly.

f. Rapid stopping.
f. Apply brakes slowly on approaching stop.


Noise in Front or Rear Wheels

a. Loose wheel lugs.
a. Tighten wheel lugs.

b. Broken or loose brake shoe return springs.
b. Replace return springs.

c. Broken or rough wheel bearings.
c. Replace bearings according to instructions.

d. Scored drums.
d. Replace brake lining and machine drums.

e. Lack of lubrication.
e. Lubricate as per instructions.


Loss of Air

a. Puncture in tire.
a. Repair puncture.

b. Faulty valve or valve core.
b. Replace valve assembly or core.

c. Rim defect.
c. Correct rim defect.

Assembly Manual