Tires Wheels Wheel Bearings Chapter 65 Tire Forces

Tires, Wheels, & Wheel Bearings Chapter 65

Tire Forces Three primary forces a tire must exert on the road surfaces are: o o o Traction Braking Cornering Tires are pneumatic which means “filled with air”

o A tool operated with air, or tire filled with air is called pneumatic

Tire – Basic parts o o o Tread-outer surface of the tire that contacts the road Body Plies-rubberized fabric and cords wrapped around the beads Belts-used to strengthen the body plies and stiffen tread Liner-thin layer of rubber bonded to the inside of the plies Sidewall-outer part of the tire that extends from the bead to the tread Beads-two rings made of steel wire, encased in rubber

Radial Tire Footprint o Very flexible sidewall with a very stiff tread – improves safety, cornering, braking, and wear

Three Types of Tire Construction

o o o Bias ply tire: this design has belts and plies running at different angles Belted bias tire: has plies that run angular from bead to bead, angle is reversed from ply to ply Radial ply tire: plies run straight across from bead to bead, stabilizer belts lie directly beneath the tread

Common tire sizing designations found on a tire side wall are… P metric and Alpha-Numeric

Tire Size Designations P-Metric

Tire Size Designations Alpha-Numeric

Tire Load Rating The load index indicates the maximum weight that a tire can accommodate vertically at a given PSI (pounds per square inch). Load Rating on Tire o (More plies=more weight) Most Passenger car tires have a maximum inflation pressure of 44 PSI

Tire Measurement Points Aspect Ratio = (Section Height/Section Width) X 100 Deflection = Free radius minus loaded radius. Free Radius = The radius of the tire/wheel assembly that is not deflected under load. Loaded Radius = Distance from wheel axis of rotation to supporting surface at a given load and stated inflation pressure. Loaded Section Height = The loaded radius minus half of the nominal rim diameter. Distance from rim seat to outer tread surface of a loaded tire. Nominal Rim Diameter = Diameter of rim seat supporting the tire bead. Examples: 13", 15" and 16. 5". Overall Width = Maximum width in cross section of unloaded tire including protruding side ribs and decorations. Revolutions Per Mile = Measured number of revolutions for a tire traveling one mile. This can vary with load and inflation. Rim Width = Linear distance between rim flanges in contact with the tire. Rolling Circumference = The linear distance traveled by a tire in one revolution. This can vary with load and inflation. Rolling circumference can be calculated as follows: 63, 360 divided by revolutions per mile = rolling circumference in inches. Section Height = Distance from rim seat to outer tread surface of unloaded tire. Section Width = Linear distance between the outsidewalls of an inflated tire without any load (exclusive of protruding side ribs and decorations). Tread Width = The portion of the tread design which comes in contact with the road.

DOT Department of Transportation Tire Sidewall Codes Decoded There is much information about the tire on it’s sidewall o o The largest type face would have to be the manufacturers make and model of tire Next in significance and prominence is tire size which is normally given as 3 values, such as P 235/75/R 15 (P-Metric) Covered on slide 6 Next you will find a number and a letter, such as 105 S. Where 105 is the load rating, in this example 2, 039 lbs (925 kg). S is the speed rating in this case up to 112 mph. M+S denotes that the tires are rated for mud and snow

DOT Department of Transportation Tire Sidewall Codes Decoded The next series of codes are the UTQG Uniform Tire Quality Grade “grading standard”. These codes denote such things as tread-wear “ 420 (higher means longer wear)”, traction “AA (best), A, B, C (worst)”, and temperature “A (higher), B, C, D (lower)”.

Tire Speed Rating Indicates the maximum permitted speed that the tire can sustain for a ten minute endurance without being in danger ! M-81 mph 130 km/h N-87 mph 140 km/h. Temporary Spare Tires P-93 mph 150 km/h Q 99 mph 160 km/h Studless & Studdable Winter Tires R-106 mph 170 km/h H. D. Light Truck Tires S-112 mph 180 km/h Family Sedans & Vans T-118 mph 190 km/h Family Sedans & Vans U-124 mph 200 km/h H-130 mph 210 km/h Sport Sedans & Coupes V-149 mph 240 km/h Sport Sedans, Coupes & Sports Cars

Tire Wear Bars o o Look in the grooves between tire tread for raised patches of rubber, called wear bars. These 2/32 -inch tall patches will help you identify a worn out tire. (In most states 3/32 -inch is the minimum legal tread depth. ) If tread is worn to a level where wear bars are flush with the tread it indicates that tread depth is 2/32 -inch or less. Replace worn tires.

Spare Tire Today, most spare tires are compact space-saver type tires that are designed for temporary use at low speeds.

Self-Sealing Tire o Self-Sealing Tire: A protective layer on the inside of the tread immediately seals holes that develop when screws or nails puncture the tire, so that no air can escape

RETREAD TIRES FOR TRUCKS & BUS o Retreaded tires are environmentally friendly. Every year in the United States, the use of retread tires saves over 400 million gallons of oil. For every 100 retread tires sold, 1500 gallons of oil can be saved! Also, each time a tire is retread, the disposal option is avoided.

Run Flat Tires Notice the heavier designed stiff sidewall Notice the PAX insert

Tire Pressure Monitoring System o A Tire Pressure Monitoring System (TPMS) is generally an electronic system designed to monitor the air pressure inside all the pneumatic tires on automobiles

Wheel - Construction o Most wheels are constructed of either steel, aluminum, or magnesium

Wheel-Construction, Drop-Center A one-piece rim with a deep center section which is lower than the two outer edges, this allows the bead of the tire to be pushed into the low area on one side while the other side is pulled over and off the Flange.

Wheel-Construction, Safety Rim o Safety rim n A rim having two safety ridges, one on each lip, to prevent the tire beads from entering the drop center area in the event of a blowout. This feature keeps the tire on the rim.

Blow-Out vs. Flat Tire Blow-out = Instant Rupture Flat Tire = Slow Leak

Valve Stems & Cores o o A rubber valve stem can be pressed through a hole in a wheel and a metal stem is secured with a nut threaded on from the outside. The purpose of the valve stem is to allow inflation and deflation of the tire The spring-loaded valve inside the stem is called the valve stem core. The spring-loaded valve pushes the valve closed when the tire inflator is removed from the stem. The valve stem caps prevent dirt and moisture from entering the valve stem.

Lug Nuts & Lug Studs o The inner face of a lug nut is tapered to center the wheel on the hub Lug studs are special fasteners made to accept lug nuts

Wheel Weights o Wheel weights balance the tire and wheel assembly, preventing vibration

Hub & Wheel Bearing Assemblies o The three basic parts of a wheel bearing Outer Bearing Race Rollers Inner Bearing Race

Non-driving Hub Assembly

Non-driving Hub Assembly o Spindle: part of the suspension system that carries the hub for the wheel. o Wheel Bearings: Mounted on a hub, they permit the spindle to rotate freely with minimum friction. o Hub: the rotating part of a car wheel assembly through which the spindle passes and the rim is attached. o o Grease Seal: keeps dirt and moisture out of the bearings. Safety Washer: Separates the bearing from the lock nut and retains pressure on the bearing. o Spindle Adjusting Nut: Adjusts the amount of play on the wheel bearing. o Nut lock: Tightens against the spindle adjusting nut locking it in place. o Cotter Pin: Keeps the lock nut from coming loose. o Dust Cap: keeps dirt and moisture out of the bearings.

Driving-Hub & Bearing Assembly Strut Upper Pivot Knuckle Hub Wishbone Sway Bar Lug Stud Tie Rod End Tie Rod Lower Control Arm Lower Ball Joint

Driving-Hub & Bearing Assembly o o o o Outer Drive Axle: Supplies power to drive wheel Ball or Roller Bearings: Hub spins freely in them Steering Knuckle: Houses the bearings, seals, hub. Connects by upper and lower ball joint pivots, and attaches to drive axle and tie rod. Drive Hub: the rotating part of a car wheel assembly through which the driveshaft/axle passes and the rim is attached. Axle Washer: Goes between the locknut and hub. Hub or Axle Locknut: Holds the axle and wheel bearings in place. Grease Seal: keeps dirt and moisture out of the bearings

Questions? o o If you can not find an answer to one of the questions on your worksheet, please submit a piece of paper to your instructor with the following information: Name, Date, Period Chapter Number Question Numbers that you could not find. Your feedback will help improve this assignment