Tire and Wheel Service Chapter 62

Objectives Adjust tire pressures correctly for all cars Rotate tires Repair tire punctures in the correct manner Determine causes of tire-related vibration Understand and perform tire balancing

Introduction Tire service is a large area of automobile repair Average owner will replace at least one set of tires Tire life defends on: Tire quality Air pressure Vehicle weight Driving conditions Suspension condition Wheel alignment

Tire Inflation Results of low tire pressure Temperature of the tire rises Load-carrying capacity of the tire is lowered Tread life is reduced Fuel consumption increases Outside edge of tire wear excessively

Checking Air Pressure Vehicle owners should check air pressure At least once a month Considerations Check when tires are cold Use accurate air pressure gauge Normally inflated radial tires have a bulging sidewall

Checking and Adjusting Tire Pressure Important points All valve stems should have screw caps Use a high quality tire gauge Tire pressure gauges are usually equipped with a pin to release air Government has mandated the installation of tire pressure monitoring systems (TPMS) on all new vehicles manufactured since 2008 Typical tire loses one psi in pressure each month

Tire Wear Four psi decrease in pressure below recommended amount Results in a 10% loss of tread life Fastest tire wear occurs during hard cornering, braking, and acceleration When tire wears within 1/16" of the bottom of its tread, wear bars become obvious Scalloped or cupped wear is caused by tire hopping up and down on road Inspect tire for physical damage

Sidewall Checks and Tire Rotation Sidewall cracks Caused by age and years of exposure Slight sidewall indentation Common characteristic of radial tires RVs and light trucks with dual rear tires Often have uneven wear on rear tires Front wheels wear the most Typical rotation for front-wheel-drive cars moves front tires to the rear on the same side

Removing and Tightening Lug Nuts Important points Removing lugs is easiest with impact wrench Tighten evenly in a crisscross pattern Lugs nuts for steel wheels and some aluminum are tapered Anti-theft nuts are popular on custom wheels Special type of lug nut is used with aluminum wheels

Repairing Wheel Studs When one or two threads are damaged They can be cleaned up with a thread chaser Broken lug bolts must be replaced

Removing and Mounting Tires on Rims Important points Tires can explode and fingers can be cut off if proper caution is not observed Tire size and construction matches wheel rating Rim diameter matches diameter on sidewall Remove valve core to deflate tire completely New tire changer design has emerged in response to needs Beads must be unseated from the bead seats Tire iron is used to remove the tire from wheel

Inspecting the Tire and Wheel and Valve Stem Service After tire is removed: inspect inside for damage Inspect wheel rim for damage Rust can damage bead seat on a wheel Valve stem service Rubber valve stems are customarily replaced when new tires are installed Can be replaced without removing tire Be careful not to damage a direct-type TPMS Do not force the tire over the sensor

Rubber Lubricant Advantages of rubber lubricant Directional tires Reduces friction between tire beads and edge of rim during mounting Helps seal around bead during initial inflation Friction between bead seats and tire bead will be reduced when inflating Directional tires Designed to be run in only one direction Indicated with an arrow

Install the Tire Major steps and considerations Clamp wheel to tire changer Install inside bead Inflate the tire Seat the beads Tubeless tires require a substantial volume of airflow for beads to start to seat on rim Most tire machines have an inflation chamber and an in-line dial indicator-type tire gauge Custom rims should be clamped from the outside

Mounting High-Performance Tires Vehicle can have many thousands of dollars invested in its tires and wheels Aftermarket wheels: $100 and $1,500 each Speed-rated tires: $600 or more each Servicing high-performance tires with tighter tire beads results in tear to bead or sidewall Low-profile tires are more apt to suffer bead damage during removal of rim Always apply rubber lubricant

Bead Roller Tire Changer Developed for use with high-performance wheels Tulip clamping system uses pads protected by rubber Removing a tire is similar to the rim clamp type Except bead is automatically pushed into drop center while bead lever tool pulls bead over rim edge Valve core should not extend above top of valve stem

Tire Runout When a tire is not correctly mounted on a rim or is out-of-round it will have runout Another possible is a out-of-round blemished tire Runout can be checked with a dial indicator

Tire Repair Important points Full water tank is used to check for leaks Mark the location of leak Inspecting tire: remove it from wheel Tire must be dry prior to inspection Check tire outside and inside

Repairing a Tire Puncture repairs can be done with a rubber tire plug and a patch Repairs can be made within tread area Opinions differ as to repairability of some tires

Preparing the Tire for Repair Important points Inside of tire liner must be cleaned Steel-belted radials should be plugged and patched Hole must be drilled or reamed first Rubber plug is inserted into the hole with vulcanizing cement Liner is lightly buffed

Patching the Tire Major steps After cleaned area dries: apply an even amount of vulcanizing cement to buffed area Remove adhesive covering and center patch over hole Roll patch into place Some plugs are a combination of plug and patch Used when the hole goes straight into the tire Liquid puncture sealants Not recommended

Tire and Wheel Balance Tire imbalance is one of several causes of vehicle vibration Wheel weights are attached to the rim to correct imbalance Several types of clip-on weights are available Lead was banned for use in wheel weights Substantial number of wheel weights fall off vehicles

Types of Wheel Balance and Couple Imbalance Wheel balancing methods: static and dynamic Static imbalance subjects wheel to vertical impacts that become worse with higher speed Couple imbalance Tire is lopsided Usually imbalance on both sides of the tire Wheel may be in static balance but not couple balance

Dynamic Balance and Computer Balancers Combination of static and couple imbalance Dynamic wheel balancers spin the wheel and locates vibration sources Computer balancers Very popular and easy to use Balance both the static and dynamic planes Tire that is dynamically balanced will also be statically balanced

Centering the Wheel on the Balancer Wheel not properly installed on wheel balancer Causes imbalance Major steps and considerations Center wheel with manufacturer method Backing plate and wheel lug flange must be clean and undamaged Hub-centric steel wheel: use a centering cone Lug-centric wheels: use lug-centering adapter Program wheel balancer after mounting

Match Mounting and Force Variation Some balancers match a tire's imbalance to a wheel's imbalance Computer determines amount the wheel and tire are out of balance Force variation Load is placed against tire: stiffness of sidewall and tire's footprint change Some come with a mark or paint dot on sidewall Some tire balancers can measure force variation

Installing the Wheel Major steps and considerations Before installing: double-check to see bolt holes in wheel are in good condition Finger-tighten lug nuts Shake wheel to center it Cross-tighten lug nuts with a torque wrench Some shops use a torque stick or torque socket to initially tighten wheel lugs using an impact wrench

Tire Pressure Monitoring System Service When tires are rotated or a defective sensor is replaced Some TPMS require the computer to be reprogrammed Different types of TPMS measuring/resetting tools TPMS sensor Replaced if it fails mechanically or electrically Special procedures are followed Tire pressure monitors Installed on vehicles that did not have them as OE