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CHAPTER 5 Tire and Wheel Service

CHAPTER 5 Tire and Wheel Service. OBJECTIVES. After studying Chapter 5, the reader will be able to: Prepare for ASE Suspension and Steering (A4) certification test content area “E” (Wheel and Tire Diagnosis and Repair). Discuss proper tire mounting procedures.

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CHAPTER 5 Tire and Wheel Service

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  1. CHAPTER 5 Tire and Wheel Service

  2. OBJECTIVES After studying Chapter 5, the reader will be able to: • Prepare for ASE Suspension and Steering (A4) certification test content area “E” (Wheel and Tire Diagnosis and Repair). • Discuss proper tire mounting procedures. • Describe recommended tire rotation methods. • Discuss how to properly balance a tire. • Describe tire repair procedures. • Explain wheel and tire safety precautions.

  3. Dynamic balance Lateral runout Match mounting Modified X Radial force variation Radial runout Shimmy Static balance Tire rotation Tramp Wheel mounting torque KEY TERMS

  4. INTRODUCTION • Proper tire service is extremely important for the safe operation of any vehicle. • Premature wear can often be avoided by checking and performing routine service, such as frequent rotation and monthly inflation checks. • Avoid overloading the vehicle and have any leaks repaired as soon as possible.

  5. FIGURE 5–1 Using soapy water from a spray bottle is an easy method to find the location of an air leak from a tire. INTRODUCTION

  6. TIRE INFLATION • Tires should always be inflated to the pressure indicated on the driver’s door or pillar sticker. • Tires should be checked when cold, before the vehicle has been driven, because driving on tires increases the temperature and therefore the pressure of the tires.

  7. TIRE INFLATION • Proper tire inflation is important for the following reasons: • Inflation pressure carries the load of the vehicle • Inflation pressure varies with temperature • Tire inflation affects fuel economy • Tire inflation affects tire life • The TREAD Act specifies that the driver be notified if the inflation of a tire drops by 25%.

  8. FIGURE 5–2 This chart shows the relationship between tire inflation pressure and load capacity of the tire. TIRE INFLATION

  9. FIGURE 5–3 This chart shows that a drop in inflation pressure has a major effect on fuel economy. TIRE INFLATION

  10. FIGURE 5–4 Notice that if a tire is underinflated by 10 PSI, the life expectancy is reduced by 40%. TIRE INFLATION

  11. What Is a “Temporary Mobility Kit”? • A temporary mobility kit is a system to inflate a flat tire supplied by the vehicle manufacturer instead of a spare tire. A temporary mobility kit can include: • A compressor powered by the cigarette lighter with stop leak. • An aerosol spray can that provides inflation and sealer.

  12. FIGURE 5–5 A temporary inflation pump that uses 12 volts from the cigarette lighter to inflate the tire. What Is a “Temporary Mobility Kit”?

  13. FIGURE 5–6 Many vehicle manufacturers include an aerosol can of sealer on vehicles that are not equipped with a conventional spare tire. What Is a “Temporary Mobility Kit”?

  14. NITROGEN INFLATION • Some shops recommend and inflate tires using nitrogen instead of using compressed air. • Compressed air contains about 78% nitrogen, 21% oxygen, and 1% other gases. • If air already contains mostly nitrogen, why use pure nitrogen?

  15. NITROGEN INFLATION • There are several reasons, including: • The nitrogen molecule is slightly larger than the oxygen molecule so the tire will lose pressure faster if air is used instead of nitrogen. • Compressed nitrogen contains less moisture than compressed air. When the tire heats up, moisture in the tire vaporizes and expands, causing the pressure inside the tire to increase. • Race teams use nitrogen because they already come to the track with a cylinder of nitrogen to power the air tools. • Race teams also have more control over how much the pressure will increase when the tires heat up, because nitrogen has less tendency to change pressure with temperature change. • Some oxygen in the tires could, over a long period of time, cause the oxidation of the inner liner of the tire and the corrosion of the wheel.

  16. FIGURE 5–7 Most shops that use nitrogen inflation install a green tire value cap to let others know that nitrogen, rather than air has been used to inflate the tire. NITROGEN INFLATION

  17. TIRE MOUNTING RECOMMENDATIONS • When removing a wheel from a vehicle for service, mark the location of the wheel and lug stud to ensure that the wheel can be replaced in exactly the same location. • Make certain that the wheel has a good, clean metal-to-metal contact with the brake drum or rotor. • Always check the rim size. • Install the tire-pressure monitoring system • Many tires have been marked with a paint dot or sticker. The tire should be mounted to the rim with this mark lined up with the valve stem.

  18. TIRE MOUNTING RECOMMENDATIONS • Never use more than 40 PSI (275 kPa) to seat a tire bead. • Rim flanges must be free of rust, dirt, scale, or loose or flaked rubber build-up prior to mounting the tire. • When mounting new tires, do not use silicone lubricant on the tire bead. Use special lubricant such as rendered (odorless) animal fat or rubber lubricant to help prevent tire rotation on the rim.

  19. FIGURE 5–8 Note the difference in the shape of the rim contour of the 16-in. and 16 1/2-in. diameter wheels. While it is possible to mount a 16-in. tire on a 16 1/2-in. rim; it cannot be inflated enough to seat against the rim flange. If an attempt is made to seat the tire bead by over-inflating (over 40 PSI), the tire bead can break, resulting in an explosive force that could cause serious injury or death. TIRE MOUNTING RECOMMENDATIONS

  20. FIGURE 5–9 When installing a tire-pressure monitoring system sensor, be sure that the flat part of the sensor is parallel to the center section of the rim. TIRE MOUNTING RECOMMENDATIONS

  21. FIGURE 5–10 This tire on a new vehicle has been match mounted at the factory. The yellow sticker is placed at the largest diameter of the tire. The valve core hole in the wheel is usually drilled at the smallest diameter of the wheel. The best way to make sure the assembly is as round as possible and to reduce the number of wheel weights needed to balance the tire is to align the sticker with the valve core. TIRE MOUNTING RECOMMENDATIONS

  22. FIGURE 5–11 (a) Cleaning the bead area of an aluminum (alloy) wheel using a handheld wire brush. The technician is using the tire changer itself to rotate the wheel as the brush is used to remove any remnants of the old tire. (b) Using an electric or airpowered wire brush speeds the process, but care should be exercised not to remove any of the aluminum itself. (Remember, steel is harder than aluminum and a steel wire brush could cause recesses to be worn into the aluminum wheel, which would prevent the tire from proper seating in the bead area.) The bead seat area on steel wheels should also be cleaned to prevent air leaks at the rim. TIRE MOUNTING RECOMMENDATIONS

  23. FIGURE 5–12 Rendered (odorless) animal fat is recommended by some manufacturers of tire changing equipment for use as a rubber lubricant. TIRE MOUNTING RECOMMENDATIONS

  24. Spin the Tires • When performing a vehicle inspection and the vehicle has been hoisted on a frame-type lift, check the tires by rotating them by hand. The tires on the nondrive wheels should spin freely. • On front-wheel-drive vehicles, rear wheels should rotate easily. • On rear-wheel-drive vehicles, front wheels should rotate easily. • On all-wheel-drive vehicles, all four wheels may require effort to rotate.

  25. WHEEL MOUNTING TORQUE • For wheel mounting torque, make certain that the wheel studs are clean and dry, and torqued to the manufacturer’s specifications. • Always tighten lug nuts gradually in the proper sequence—star pattern (tighten one nut, skip one, and tighten the next nut). • This helps prevent warping the brake drums or rotors, or bending a wheel.

  26. FIGURE 5–13 Always tighten wheel lug nuts (or studs) in a star pattern to ensure even pressure on the axle flange, brake rotors or drums, and the wheel itself. WHEEL MOUNTING TORQUE


  28. Fine-Tune Handling with Tire-Pressure Changes • The handling of a vehicle can be changed by changing tire pressures between the front and rear tires. • Understeer • Oversteer

  29. FIGURE 5–14 Most manufacturers recommend using hand tools rather than an air impact wrench to remove and install lock-type lug nuts to prevent damage. If either the key or the nut is damaged, the nut may be very difficult to remove. WHEEL MOUNTING TORQUE

  30. FIGURE 5–15 A torque-limiting adapter for use with an air impact wrench still requires care to prevent overtightening. The air pressure to the air impact should be limited to 125 PSI (860 kPa) in most cases, and the proper adapter must be selected for the vehicle being serviced. The torque adapter absorbs any torque beyond its designed rating. Most adapters are color coded for easy identification as to the size of lug nut and torque value. WHEEL MOUNTING TORQUE

  31. TIRE ROTATION • To ensure long life and even tire wear, tire rotation is essential. • It is important to rotate each tire to another location. • Some rear-wheel-drive vehicles, for example, may show premature tire wear on the front tires.

  32. I Thought the Lug Nuts Were Tight! • Proper wheel nut torque is critical, as one technician discovered when a customer returned complaining of a lot of noise from the right rear wheel. SEE FIGURE 5–16 for a photo of what the technician discovered. The lug (wheel) nuts had loosened and ruined the wheel.

  33. FIGURE 5–16 This wheel was damaged because the lug nuts were not properly torqued. I Thought the Lug Nuts Were Tight!

  34. FIGURE 5–17 The method most often recommended is the modified X method. Using this method, each tire eventually is used at each of the four wheel locations. An easy way to remember the sequence, whether front wheel drive or rear wheel drive, is to say to yourself, “Drive wheels straight, cross the nondrive wheels.” TIRE ROTATION

  35. FIGURE 5–18 Tire showing excessive shoulder wear resulting from underinflation and/or high-speed cornering. TIRE INSPECTION • All tires should be carefully inspected for faults in the tire itself or for signs that something may be wrong with the steering or suspension systems of the vehicle.

  36. FIGURE 5–19 Tire showing excessive wear in the center, indicating overinflation or heavy acceleration on a drive wheel. FIGURE 5–20 Wear on the outside shoulder only is an indication of an alignment problem. TIRE INSPECTION

  37. All-Wheel-Drive Tire Concerns • It is very important that all-wheel-drive vehicles be equipped with tires that are all the same outside diameter. If, for example, the vehicle has 20,000 miles and the tires are half worn, all of the tires should be replaced in the event of a problem requiring replacement of only one tire. • Most vehicle manufacturers specify that all tires must be within 2/32 in. of tread depth without causing a constant strain on the drive train.

  38. RADIAL RUNOUT • Even though a tire has no visible faults, it can be the cause of vibration. • If vibration is felt above 45 mph, regardless of the engine load, the cause is usually an out-of-balance or a defective out-of-round tire. • Both of these problems cause a tramp or up-and-down-type vibration. • If the vibration is seen in the hood of the vehicle or felt in the steering wheel, then the problem is usually the front tires. • If the vibration is felt throughout the entire vehicle or in the seat of your pants, then the rear tires (or drive shaft, in rear-wheel-drive vehicles) are the problem.

  39. FIGURE 5–21 A tire runout gauge being used to measure the radial runout of a tire. FIGURE 5–22 To check wheel radial runout, the dial indicator plunger tip rides on a horizontal surface of the wheel, such as the bead seat. RADIAL RUNOUT

  40. RADIAL RUNOUT • To check radial runout (checking for out-of-round) and lateral runout (checking for side-to-side movement), follow these steps: • Raise the vehicle so that the tires are off the ground approximately 2 in. (5 cm) • Place the runout gauge against the tread of the tire in the center of the tread and, while rotating the tire, observe the gauge reading • Note that maximum radial runout should be less than 0.060 in. (1.5 mm). • Check all four tires

  41. I Thought Radial Tires Couldn’t Be Rotated! • When radial tires were first introduced by American tire manufacturers in the 1970s, rotating tires side-to-side was not recommended because of concerns about belt or tread separation. Since the late 1980s, most tire manufacturers throughout the world, including the United States, have used tire-building equipment specifically designed for radial-ply tires. These newer radial tires are constructed so that the tires can now be rotated from one side of the vehicle to the other without fear of causing a separation by the resulting reversal of the direction of rotation.

  42. RADIAL RUNOUTCORRECTING RADIAL RUNOUT • Excessive radial runout may be corrected by one of several methods: • Try relocating the wheel on the mounting studs. • Remount the tire on the wheel 180 degrees from its original location. • If runout is still excessive, remove the tire from the wheel and check the runout of the wheel.

  43. Is the Age of a Tire Important? • Yes. The National Highway Traffic Safety Administration (NHTSA) recommends that any tire six years old or older should be replaced regardless of tread depth. This means that tires that look almost like new but are six years old or older should be replaced because the NHTSA determined that age, not tread depth, was a major factor in tire failures.

  44. LATERAL RUNOUT • Another possible problem that tires can cause is a type of vibration called shimmy. • This rapid back-and-forth motion can be transmitted through the steering linkage to the steering wheel. • Excessive runout is usually noticeable by the driver of the vehicle as a side-to-side vibration, especially at low speeds between 5 and 45 mph (8 and 72 km/h). • Shimmy can be caused by an internal defect of the tire or a bent wheel. • This can be checked using a runout gauge on the side of the tire or wheel to check for lateral runout.

  45. FIGURE 5–23 To check lateral runout, the dial indicator plunger tip rides on a vertical surface of the wheel, such as the wheel flange. LATERAL RUNOUT

  46. FIGURE 5–24 The most accurate method of measuring wheel runout is to dismantle the tire and take dial indicator readings on the inside of the wheel rim. LATERAL RUNOUT

  47. The Greased Wheel Causes a Vibration • Shortly after an oil change and a chassis lubrication, a customer complained of a vibration at highway speed. The tires were checked for excessive radial runout to be certain the cause of the vibration was not due to a defective out-of-round tire. After removing the wheel assembly from the vehicle, excessive grease was found on the inside of the rim. Obviously, the technician who greased the lower ball joints had dropped grease on the rim. After cleaning the wheel, it was checked for proper balance on a dynamic computer balancer and found to be properly balanced. A test-drive confirmed that the problem was solved.

  48. LATERAL RUNOUTCORRECTING LATERAL RUNOUT • Excessive lateral runout may be corrected by one of several methods: • Re-torque the wheel in the proper star pattern to the specified torque. Unequal or uneven wheel torque can cause excessive lateral runout. • Remove the wheel and inspect the wheel mounting flange for corrosion or any other reason that could prevent the wheel from seating flat against the brake rotor or drum surface. • Check the condition of the wheel or axle bearings. Looseness in the bearings can cause the wheel to wobble.

  49. TIRE BALANCING • Proper tire balance is important for tire life, ride comfort, and safety. • Tire balancing is needed because of the lack of uniform weight and stiffness (due to splices) and a combination of wheel runout and tire runout. • Balancing a tire can compensate for most of these conditions. • However, if a tire or wheel is excessively out of round or bent, then replacement of the wheel or tire is required.


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