All passenger car models carry 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, 14 1/8" in diameter.
The tires used on all models except the nine passenger station wagon, are of the 7.50-14 size with a 4 ply rating. The nine passenger station wagon utilizes a 7.50-14 6 ply tire. 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.
Testing Tire Pressures
Puncture Inspection
Changing Road Wheels
Interchanging Tires
Cleaning Whitewall Tires
Testing Tire Pressures
The correct tire pressure for all 4 ply tires is 22 pounds front and rear. For 6 ply tires, such as used on the 9 passenger station wagon, 28 pounds is the recommended pressure. 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 Pressures-22 lbs. when car has been standing three hours or driven less than a mile.
City Pressure-25 lbs. after driving car three miles or more below 40 miles per hour.
Highway Pressure-26 pounds after driving car three miles or more above 40 miles per hour.
The pressures do not increase more than 4 pounds when heated under hard driving. 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.
CAUTION: On models equipped with discs, index the pilot
hole in the disc on the valve stem. (To insure that the antirotation
notches in wheel disc register on lugs in wheel rim.)
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
Dismounting and Mounting Tires
Tire and Rim Repair
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 braking 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 comers 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'", 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 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 has 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 tubeless tires presents no problems if the correct procedures are used and the following precautions observed.
The general procedure is the same as for tube and tire installation except that extreme care must be exercised to prevent injury to the sealing bead and circumferential bead when forcing tire over rim.
Newly designed tire mounting machines or tire irons should be used.
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 Range. The weight
of the tire will seat the bottom bead.
Tire and Rim Repair
Different types of tubeless tire repair equipment and various methods of repair are recommended by the tire manufacturers. The two methods recommended by Chevrolet are as follows:
With this method the patch uses its own fuel to be ignited when vulcanization takes place. This method is recommended for repairing punctures not exceeding 3/16" in diameter. Size of puncture can be determined by size of puncturing object.
Through the use of self-vulcanizing outside plug repair kits currently on the market, passenger car tubeless tire punctures can now be permanently repaired without dismounting the tire from the rim and in many cases, without removing the wheel from the car.
Punctures which cannot be repaired, are those which are over 3/16-inch diameter, or leaks caused by incisions or ragged lacerations. Outside plug repairs can be made on all passenger car tubeless tires including those containing soft puncture sealing material.
The following procedure should be followed in using these kits.
NOTE: If the puncture is an irregular cut that will not seal completely by this method, a self-vulcanizing patch or hot patch repair should be made.
In this method, a chemical action vulcanizes the patch. No external source of heat is necessary. Maximum size of puncture hole must not exceed 3/1(;" for this method of patching. (Larger size injuries must be repaired with press type vulcanizing equipment.) Many kits are manufactured and may be procured locally.
NOTE: This method should be used only for tires without soft puncture sealing material. The following procedure should be followed in using this kit.
Rim Repair
Valve Assembly-Replace
Static Balance
Dynamic Balance
Static Balance
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:
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.
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 1/6 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."
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 (22 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.
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.
