Questions and Answers
If a truck is carrying 20% more weight than it was spec'd for, how much should tire pressures be increased to compensate?
Over-inflation does not compensate for overloads.
What is the first step torque setting usually specified when using the TMC recommended practice (RP 618A) method of setting bearing endplay on commercial truck wheel ends?
200 lb-ft (270 N.m)
Technician A says that all tires of the same nominal diameter have the same rolling radius. Technician B says that to determine the rolling radius of a truck tire, measure the periphery using a tape measure and divide the result into one mile. Who is correct?
Neither A nor B.
What is the torque required for wheel installation in a ConMet unitized hub system?
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Technician A says that to cure a cracked rim that is leaking air out of tires, an inner tube should be installed. Technician B says that a cracked rim can be repaired by welding using an E-7018 electrode. Who is correct?
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Technician A says that tire pressures should always be checked when the tires are at operating temperature. Technician B says that the pressure rise that takes place from a cold tire to one at operating temperature is usually around 10% in a truck tire. Who is correct?
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When matching tires on a tandem drive axle truck with dual wheels, what should be true?
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Where should the spacer ring be placed when mounting a set of duals to a cast spoke wheel?
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What types of spacer band can be used on truck cast spoke wheel assemblies?
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Which of the following is a major advantage of a cast spoke wheel when compared with a stud-piloted disc wheel?
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Technician A says that OSHA requires any technician to have training before working on tires mounted with split rims. Technician B says that large numbers of trashed tires represent a major fire hazard and most jurisdictions have tire disposal regulations. Who is correct?
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Technician A says that cast spoke wheels for heavy-duty trucks are cast with 3, 4, or 6 spokes. Technician B says that a cast spoke wheel with 6 spokes is most likely to be found on a heavily loaded front axle. Who is correct?
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What does the term '18-wheeler' refer to?
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Technician A says that dynamic spin balancing of tire/wheel assemblies on the truck is generally the OEM preferred method. Technician B says that injecting commercial balancing fluid into tires is an accepted means of ensuring wheels are dynamically balanced. Who is correct?
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Which of the following is true regarding an 18-wheeler?
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Technician A says that automatic tire pressure control systems (TPCS) can often pay for themselves during the life of a truck due to reduced tire costs. Technician B says that TPCS systems must be spec'd to new truck and may not be retrofit to current trucks. Who is correct?
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After completing a TMC wheel end adjustment, how can one confirm that the adjustment is as specified?
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What method should be used to adjust wheel bearings on all non-unitized wheel hubs?
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Which of the following correctly describes how most commercial highway truck wheel bearings are lubricated?
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Technician A says that after replacing the drive axle tires on a highway tractor, the new revolutions per mile data must be programmed to the chassis data bus. Technician B says that the previous programming data is still valid providing the tires are of the same nominal dimension. Who is correct?
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Which of the following is a typical cold inflation pressure of a heavy-duty truck radial tire?
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Which of the following safety precautions should be adhered to when inflating truck tires?
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Study Notes
Tire Load and Pressure
- Over-inflation is insufficient to compensate for a truck carrying 20% more weight than specified.
Bearing Endplay Adjustment
- The first step torque setting for bearing endplay on commercial truck wheel ends is typically 200 lb-ft (270 N.m) using TMC recommended practice (RP 618A).
Tire Rolling Radius
- Rolling radius of tires is not the same for all tires of the same nominal diameter.
- Correct rolling radius measurement involves measuring periphery and dividing by one mile.
Wheel Installation Torque
- Required torque for wheel installation in a ConMet unitized hub system is 300 lb-ft (407 N.m).
Rim Repair Misconceptions
- Cracked rims leaking air should not be repaired with an inner tube or welding using E-7018 electrode.
Tire Pressure Monitoring
- Tire pressures should be checked at operating temperature; a typical pressure rise from cold to operating temperature is around 10% in truck tires.
Matching Tires on Tandem Axles
- All drive axle tires on tandem drive axle trucks must match in nominal size and type of construction.
Dual Wheel Mounting
- Spacer rings when mounting duals on a cast spoke wheel should be placed between the inboard and outboard tires.
Spacer Bands for Cast Spoke Wheels
- All types of spacer bands are applicable for truck cast spoke wheel assemblies.
Advantages of Cast Spoke Wheels
- Major advantage of cast spoke wheels compared to stud-piloted disc wheels is lighter weight.
Safety and Regulations
- OSHA mandates training for technicians working on tires with split rims; improper disposal of tires poses a fire hazard, subject to regulations.
Spoke Count in Heavy-Duty Wheels
- Cast spoke wheels for heavy-duty trucks may have 3, 4, or 6 spokes; 6-spoke wheels are not commonly found on heavily loaded front axles.
Definition of 18-Wheeler
- The term "18-wheeler" describes a dual drive axle tractor combined with a dual axle trailer, totaling 18 wheels.
Dynamic Balancing Methods
- Dynamic spin balancing is typically the OEM preferred method for balancing tire/wheel assemblies on trucks.
- Injecting commercial balancing fluid into tires is an accepted alternative for dynamic balance.
Automatic Tire Pressure Control Systems (TPCS)
- TPCS can lead to reduced tire costs and may pay for themselves over the truck's lifecycle but must be specified for new trucks without retrofitting.
Wheel End Adjustment Confirmation
- Confirm proper wheel end adjustment by measuring endplay to be between 0.001-inch to 0.005-inch (0.025 to 0.127 mm) with a dial indicator.
Wheel Bearing Lubrication
- Most commercial highway truck wheel bearings are lubricated with a wet (oil bath) hub system.
Tire Data and Programming
- After replacing drive axle tires, programming of new revolutions per mile data is necessary; previous data remains valid if tires are same nominal dimensions.
Cold Inflation Pressure
- Typical cold inflation pressure for heavy-duty truck radial tires is 100 psi (690 kPa).
Tire Inflation Safety Precautions
- Adhere to all recommended safety precautions when inflating truck tires to prevent accidents.
Wheel Types and Load Capacity
- Consideration for maximum load capacity is crucial when selecting appropriate wheel types for specific applications.
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Description
Test your knowledge on wheels and tires from Chapter 27. This quiz covers essential concepts such as tire pressure adjustments for weight and proper torque settings for bearings. Perfect for students and professionals in the automotive field.
