Chapter 3: Tires & Wheels
What is the meaning of the service description 88H on the tire side wall following the tire size?
88 stands for the tire's load rating which indicates it can carry a total load capacity of 1,235 lbs. H indicates the tire's speed rating, suggesting the tire can perform within it's limitations at a top speed of 130 mph.
Replacement tires must be the same type and size as the original tires to maintain vehicle safety. A. True B. False
A. True
Replacement tires can have varying ratings as the original tires and still maintain vehicle safety. A. True B. False
B. False Replacement tires MUST have the same ratings as the original tires to maintain vehicle safety.
Have steel or polyester belts between the cord plies and the tread.
Belted bias-ply tires
A type of tire construction with the cord plies wound at an angle to the center of the tire and no belts surrounding the cords.
Bias-ply tires
Describe the structural difference between a bias-ply and radial-ply tire.
Bias-ply tires have cords that criss-cross each other, whereas radial-ply tires have cords arranged at 90 degree angle. This allows for radial tires to provide better steering, tread life, and less rolling resistance than bias-ply tires.
A condition where the plies and/or belts are not level across the tire tread. May cause the vehicle to pull in one direction when driven.
Conicity
Refers to the balance of a wheel in motion.
Dynamic balance
What causes wheel shimmy, increased tire wear, unstable directional control, driver fatigue, and increased wear on suspension and steering components?
Dynamic wheel unbalance
State general tire functions.
Improved cushioning for comfort. Support car weight. Develop traction when needed. Keep car directionally stable. Absorb road impacts.
Interpret what each item of a tire size means, using P225/45R16 as your example.
P is the letter given indicating what type of vehicle the tire is intended for (e.g., P = passenger). 225 is the tire's width measured in millimeters. 45 indicates the tire's aspect ratio, which is it's height-to-width ratio represented as a percentage. The aspect ratio of this tire indicates the tire's height is 45 percent of its width. R stands for radial construction which provides increased tread life, reduced rolling resistance, and improved steering when compared to a bias-ply tire. 16 is the size of the rim's diameter written in inches.
What are the 3 different types of tire repair?
Patch Plug Patch & Plug
A condition that occurs when tire sidewalls do not have equal stiffness around their complete area.
Road force variation
What are the four types of specialty tires?
SUV/4X4 Puncture sealing Mud and snow All-season
The balance of a wheel in the stationary position.
Static balance
What causes wheel tramp and severe tire cupping?
Static wheel unbalance
What is the tire DOT code and how do you know the date the tire was manufactured?
The Department of Transportation code is a set of numbers and letters which are stamped on the tire sidewall. These indicate where the tire originated from and the manufacturing date. The last 4 numbers demonstrate the date the tire was manufactured. The first two numbers indicate the week and the last two the year.
Define tire contact area and tire deflection.
The tire contact area is the area of the tire that contacts the road. Tire deflection occurs when tire tread envelopes excess rubber which prevents the tire from scrubbing, thus significantly reducing the amount of tread wear. This all occurs in between the road and the tire contact area.
Explain the purpose of the wheel rim drop center and safety ridges.
The wheel rim drop center enables technicians to more conveniently install and remove the tire from the rim. Safety ridges, or bead look ridges, are located behind the tire bead. These help keep the beads from moving and disengaging the tire from the rim in the event of a blowout.
List and define the three major uniform tire quality grading system ratings.
There are three major UTQG rating systems used with tires. The tread wear rating indicates to the customer the tire's tread life. The traction rating measures the tire's ability to provide traction under wet conditions. The temperature rating indicates the tire's ability to produce and manage heat while driving.
Information molded on the tire sidewall indicating that the tire meets the manufacturer's performance standards for traction, endurance, dimensions, noise, handling, and rolling resistance.
Tire performance criteria (TPC)
Information including tread wear, traction, and temperature ratings that is molded into the tire sidewall, and is required by the Department of Transportation (DOT).
Uniform Tire Quality Grading (UTQG) System
Rapid upward and downward wheel and tire oscillations.
Wheel tramp
Describe the results of static unbalance.
When a tire is statically unbalanced, a heavy spot at one location of the tire will cause tire tramp. Tire tramp involves the tire lifting up off the road and coming back down with a greater force. This occurs because, due to centrifugal force and strong acceleration, the heavy spot in the tire moves on a tangential line away from the wheel's axis. Over time this can cause cupping and scuffing to the tire tread
Explain the difference between an A and C tire temperature rating.
Where C rated tires can only withstand temperatures found between 85 to 100 mph, an A rating increases this tolerance to 115 mph.
Replacement tires should be installed in pairs on the same __________ .
axel
To calculate the tire aspect ratio, the tire section __________ is ___________ by the __________.
height is divided by the width
__________ occurs when water on the pavement is allowed to remain between the pavement and the tire tread contact area.
hydroplaning
Tires equipped on today's passenger cars and light trucks are of the __________ ply design.
radial
In ___________ __________ , the ply cords are arranged radially at a right angle to the tire centerline.
radial-ply tires
