Wheels

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Wheels Tires
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Contents

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

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Wheels

• 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

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Wheel Assembly
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Mag Wheels

• Aluminum or magnesium wheelsare often called
  mags

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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

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Drop-Center Wheel

• Note the smaller diameter in thecenter of the rim

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Dimensions of a Wheel
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Safety Rims

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

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Valve Stems and Cores

• 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

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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
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Tires

• 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

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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

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Tubeless Tire
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Parts of a Tire
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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

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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

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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

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Bias Ply Tire
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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

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Belted Bias Tire
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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

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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

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Radial Ply Tire
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Tire Sidewall Markings
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Tire Size

• Alpha-NumericUses letters and numbers to denote
  tire size in inches and its load-carrying
  capacity in pounds

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Tire Size

• P-MetricUses metric values and international
  standards

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Tire Size
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Tire Size

• If you switch tire size on a car you can mess up
  the speedometer to figure out how close you are
  do the math to figure out the diameter.
• For a 205/75R15 tire it would look like this
• 205 X .75 x 2 25.4 15 27.106
• Tire size X Aspect ratio X 2 25.4 Rim size
• 100

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Points of Measurement
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Aspect Ratio

• Height-to-width ratio of a tire. Comparison of a
  tires height and width

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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

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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)

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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

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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

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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

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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

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Wear Bars

• When too much tread has worn away, solid rubber
  bars will show up across the tread

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Compact Spare Tire

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

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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

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Self-Sealing Tire Action

• A. Nail punctures tire
• B. Nail is pulled out
• C. Sealing compound flows into the hole

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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

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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

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Run-Flat Tires
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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

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Pressure Sensor
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System Operation
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Tire Maintenance

• Maintenance procedures include periodic
  inspection, checking inflation pressure, and tire
  rotation
• These maintenance steps help ensure safety and
  longer tire life

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Checking Tire Inflation Pressure

• Remove valve stem cap
• Press the tire gauge squarely over the stem
• Compare reading to the maximum pressure printed
  on the tire sidewall or operators manual
• Adjust as necessary
• Reinstall the cap

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Tire Service Tools
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Rotating Tires

• Ensures maximum tire life
• Front and rear tires wear differently
• Rotation helps even out tire wear
• Tires are rotated at intervals such as every 3000
  miles (5000 km)

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Tire Rotation Patterns
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Lug Nuts, Studs, and Bolts

• 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

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Lug Nut and Stud

• Stud is pressed into the hub oraxle flange

If metric or left-hand threads are used, markings
will normally be given
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Torquing Lug Nuts

• Torque is very important, especially on vehicles
  with mag wheels and lightweight hubs
• Overtorquing can cause wheel and hub distortion,
  or brake pulsation
• Undertorquing might allow the lug nuts to loosen
  and the wheel to fall off

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Torquing Lug Nuts

• Torque nuts to specifications in a crisscross
  pattern

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Replacing Lug Studs

• Lug studs can become stripped or worn
• Force out the old stud with a pressing tool
• To install new studs, use flat washers and a lug
  nut
• Draw the new stud into place by tightening the
  nut on the washers
• If the hub is removed from the vehicle, a
  hydraulic press can be used

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Hub and Wheel Bearing Assemblies

• Reduces friction by allowing the wheel to turn
  freely around the spindle, in the steering
  knuckle, or in the bearing support
• Three types of bearings
• ball bearing
• roller bearings
• tapered roller bearings (most common)

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Ball Bearing

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

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Tapered Roller Bearing

• Lubricated with high-temperature grease

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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

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Hub and Wheel Bearing(Nondriving Wheels)
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Hub and Wheel Bearing(Nondriving Wheels)

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

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Hub and Wheel Bearing(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

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Hub and Wheel Bearing(Driving Wheels)
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Hub and Wheel Bearing(Driving Wheels)

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

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Hub and Wheel Bearing (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

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Hub and Wheel Bearing (Four-Wheel Drive)

• Front axle, brakes, hub, and wheel bearing
  assembly