Tires: Description and Operation

Description and Operation

General Description

The factory-installed tires are designed to operate with loads up to and including the full rated load capacity when these tires are inflated to the recommended pressures.
The following factors affect tire life:
- Tire pressures
- Wheel alignment
- Driver techniques
- Heavy cornering
- Overly rapid acceleration
- Heavy braking

Tire Inflation Description

When you inflate the tires to the recommended inflation pressures, the factory-installed wheels and tires are designed to handle loads to the tire's rated load capacity. Incorrect tire pressures, or under-inflated tires, can cause the following conditions:
- Vehicle handling problems
- Poor fuel economy
- Shortened tire life
- Tire overloading
Check the tire pressure when the following apply:
- The tires are cool.
- The vehicle has not been driven for more than 3 hours.
- The vehicle has been driven less than 1.6 km (1 mi).
Check the tires monthly or before any extended trip. Adjust the tire pressure to the specifications on the tire label Install the valve caps or extensions on the valves. These keep out dust and water.
The kilopascal (kpa) is the metric term for pressure. The tire pressure may be printed in both kilopascal (kpa) and psi. One psi equals 6.9 kPa.
Tires with a higher than recommended pressure can cause the following conditions:
- A hard ride
- Tire bruising
- Rapid tread wear at the center of the tire
Tires with a lower than recommended pressure can cause the following conditions:
- A tire squeal on turns
- Hard steering
- Rapid wear and uneven wear on the edge of the tread
- Tire rim bruises and tire rim rupture
- Tire cord breakage High tire temperatures
- Reduced vehicle handling
- High fuel consumption
- Soft riding
Unequal pressure on the same axle can cause the following conditions:
- Uneven braking
- Steering lead
- Reduced vehicle handling

Replacement Tires Description

Caution: Do not mix different types of tires on the same vehicle such as radial, bias, and bias-belted tires except in emergencies because vehicle handling may be seriously affected and may result in loss of control and possible sedous injury.

Important: Install new tires in pairs on the same axle. If you need to replace only one tire, this should be paired with the tire that has the most tread.

A Tire Performance Criteria (TPC) specification number is molded in the sidewall near the tire size of all original equipment tires. This number ensures that the tire meets performance standards for traction, endurance, dimension, noise, handling, rolling resistance, and others. A specific TPC number usually is assigned to each tire size.
Replacement tires should be the same size, load range, and construction as the original tires. Replace the original tires with tires that have the same TPC specification number. Use of any other tire size or type may seriously affect the following items:
- Vehicle ride
- Vehicle handling Speedometer/odometer calibration
- Vehicle ground clearance
- Tire clearance to the body and chassis
Replace tires when you find the following conditions:
- The tires are worn to a point where 1.6 mm (1/16 in) or less tread remains, or, the cord or fabric shows. The tires may have built-in tread wear indicators that appear between the tread grooves when the tread is 1.6 mm (1/16 in) or less. When the indicators appear in two or more adjacent grooves at three spots around the tire, replace the tire.
- The tread or sidewall is cracked, cut, or snagged deep enough to expose the cord or the fabric.
- The tire has a bump, bulge, or a split. Slight sidewall indentations are normal and this should not affect ride.
- The tire has a puncture, a cut, or other damage that cannot be repaired correctly because of the size or location of the damage.

All Seasons Tires Description

Most vehicles are now equipped with steel belted, all-season radial tires as standard equipment. These tires provide a soft, quiet ride, good handling, and long tread life. These tires provide all-season traction and low rolling resistance in order to help improve fuel economy.
These tires have higher snow traction than non all-season radial tires previously used. For this reason, these qualify as snow tires. You can identify these tires by an M+S molded in the tire sidewall after the size. The suffix MS also is molded in the sidewall after the TPC specification number.

P-Metric Sized Tires Description

Most P-metric tires do not have exactly corresponding alpha/numeric tire sizes. A P205175/R15 is not equal in size and load carrying capacity to an FR78-1 5. Because of this, replacement tires should be of the same TPC specification number (size, load range, and construction) as those originally on the vehicle. If you must replace P-metric tires with other sizes, consult a tire dealer. Tire companies can best recommend the closest match.
Identify radial-ply by the letter R or Radial on the sidewall. Encoded on the side wall are the tire type, the tire size, and the aspect ratio (eg. P205/75R1 5).




The following are the code designations:
- P is passenger car (LT is light trucks)
- 205 is the section width (1) of the tire
- R is the radial type design construction
- 75 is the aspect ratio (2) (height to width ratio)
- 15 is the rim diameter in inches
An all-season tire has either M+S, MAMPSS, or M-S imprinted on the sidewall.

Tire Placard Description

The tire information label is on the rear face of the drivers door. Refer to this label for tire information. The label lists the following items:
- Maximum vehicle load
- Tire size
- Cold inflation pressure