modern automotive technology

© Goodheart-Willcox Co., Inc.

by

Russell Krick

Publisher

The Goodheart-Willcox Co., Inc.Tinley Park, Illinois


Tires Wheels Valve stems and cores Lug nuts, studs, and bolts Wheel weights Hub and wheel bearing assemblies


Tires perform two basic functions: act as a soft cushion between the road

and the metal wheel provide adequate traction (friction) with

the road surface


Tire Types Pneumatic

filled with air internal air pressure pushes out on the

inside of the tire to support the vehicle Tubeless tire

does not use an inner tube tire and wheel form an airtight unit

Tube-type tire uses an inner tube to hold air pressure


Tubeless Tire


Parts of a Tire


Tire Rolling Resistance Measurement of the amount of friction

produced as the tire operates on the road surface

High rolling resistance increases fuel consumption and wear

Rolling resistance is reduced by higher inflation pressure, tire design, and a lighter vehicle


Tire Construction There are many design variations:

different numbers of plies may be used plies may run at different angles different materials may be used

Three types of tires used on automobiles: bias ply belted bias tire radial tire


Bias Ply Tire Plies run on an angle from bead to

bead Angle is reversed from ply to ply Does not use belts Body of the tire flexes easily Provides a smooth ride Plies and tread are weakest

reduces traction at high speeds increases rolling resistance


Bias Ply Tire


Belted Bias Tire Bias tire with belts added to increase

tread stiffness Belts lie under the tread area only Two stabilizer belts and two or more

plies improve tire performance provides a smooth ride and good traction reduces rolling resistance


Belted Bias Tire


Radial Ply Tire

Plies run straight across from bead to bead

Stabilizer belts lie beneath the tread Belts can be made of steel, flexten,

fiberglass, or other materials


Radial Ply Tire

Uses a very flexible sidewall with a stiff tread provides a very stiff footprint improves safety, cornering, braking, and

wear may produce a harsher ride at low speeds


Radial Ply Tire


Tire Sidewall Markings


Tire Size

Alpha-Numeric–Uses letters and numbers to denote tire size in inches and its load-

carrying capacity in pounds


Tire Size

P-Metric–Uses metric values and international standards


Points of Measurement


Aspect Ratio

Height-to-width ratio of a tire. Comparison of a tire’s height and width


Maximum Load Rating Amount of weight the tire can carry at

the recommended inflation pressure Printed on the sidewall P-metric:

given in kilograms and pounds

Alpha-numeric: indicated by a letter such as B, C, or D


Maximum Inflation Pressure

Highest air pressure that should be pumped into the tire

Many tires have a maximum recommended pressure of 32 to 40 psi (220 to 275 kPa)


Tread Plies Number of plies and ply rating:

2-ply 2-ply with a 4-ply rating 4-ply

Greater number of plies usually indicates a greater load-carrying capacity


DOT Serial Number Identifies the manufacturer, plant,

location, construction, and date of manufacture

Stamped into the sidewall Department of Transportation rating

means the tire has passed prescribed safety tests


Tire Grades Tread wear

given as a number, 100 to 500 higher number is more resistant to wear

Tire traction given as an A, B, or C “A” rating has the most traction

Tire temperature resistance given as an A, B, or C “A” rating resists temperature buildup best


Speed Rating

Maximum allowable sustained road speed a tire can safely withstand without failure

Ratings range from B to Z “B” rating 31mph or 50 km/h “Z” rating 149 mph or 238 km/h


Wear Bars

When too much tread has worn

away, solid rubber bars will show up across the tread


Compact Spare Tire

This is a high pressure spare, requiring60 psi (415 kPa)


Self-Sealing Tires

Coating of sealing compound is applied to the liner

If a nail punctures the tire, air pressure will push the soft compound into the hole to stop air leakage


Self-Sealing Tire Action

A. Nail punctures tire

B. Nail is pulled out

C. Sealing compound flows into the hole


Retreads

Used tires that have had a new tread vulcanized to the old carcass, or body

Large truck tires are often recapped because of the high cost of new truck tires


Run-Flat Tires

Use extremely stiff sidewall construction

Still usable with a loss of air pressure Tire will still retain most of its shape

because the sidewall is strong enough to support vehicle weight


Run-Flat Tires


Tire Inflation Monitoring System

Often used with run-flat tires Pressure sensors are mounted on each

wheel If tire pressure is not correct, the wheel

sensor produces a radio signal Signal is received by a module that

turns on a dash warning light


Pressure Sensor


System Operation


Designed to support the tire while withstanding loads from acceleration, braking, and cornering

Made of steel, aluminum, or magnesium

Lightest weight is desirable to reduce “unsprung” weight, improving handling


Wheel Assembly


Mag Wheels

Aluminum or magnesium wheelsare often called “mags”


Drop-Center Wheel Allows for easier installation and

removal of the tire Center of the wheel is smaller in

diameter than the rim When installing a tire, it can fall into the

recess, then, the other side of the tire bead can be forced over the rim


Drop-Center Wheel

Note the smaller diameter in thecenter of the rim


Dimensions of a Wheel


Safety Rims

Small ridges on the rim hold the tire on the wheel during a tire blowout or flat


Valve stem pressed into a hole in the wheel of a

tubeless tire to allow inflation and deflation

Valve core spring-loaded air valve that is threaded

into the valve stem Valve cap

protects the air valve and stem threads from dirt, moisture, and damage


Valve Stem Assembly

Valve stem snaps into the holein the wheel

Press fit forms an airtight seal

Valve core screws into the

valve stem body


Lug nuts hold the wheel and tire assembly on the

vehicle Lug studs

special studs that accept the lug nuts Lug bolts

used instead of nuts screw into threaded holes in the hub or

axle flange


Lug Nut and Stud

Stud is pressed into the hub or

axle flange

If metric or left-hand threads are used,

markings will normally be given


Small lead weights Attached to the wheel rim to balance

the wheel-and-tire assembly Used to offset a heavy area of the

wheel and tire


Allow the wheel to turn freely around the spindle, in the steering knuckle, or in the bearing support

Most wheel bearings are tapered roller bearings or ball bearing


Tapered Roller Bearing

Lubricated with high-temperature grease


Ball Bearing

Balls allow parts to rotate with a minimum amount of friction and wear


Hub and Wheel Bearing

(Nondriving Wheels)

Spindle is stationary, providing a mounting place for the wheel bearings, hub, and wheel

Hub is partially filled with grease to lubricate the bearings

Nut on the end of the spindle allows adjustment of the bearing preload



(Nondriving Wheels)



(Nondriving Wheels)

Used on the front of rear-wheel-drive cars or the rear of front-wheel-drive cars



(Driving Wheels) Axle shaft rotates inside a stationary

support Drive shaft fits through the center of the

bearings Hub is splined to the axle shaft Ball bearings are lubricated by thick,

high-temperature grease



(Driving Wheels)



(Driving Wheels)

Commonly used on the front of front-wheel-drive vehicles



(Four-Wheel Drive) Front drive axle extends through a

stationary spindle Special free-wheel, or locking hub

transfers power from the axle to the hub-disc assembly when in four-wheel-drive



(Four-Wheel Drive)

Front axle, brakes, hub, and wheel bearing assembly

modern automotive technology

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