Tires 101
Tire Type
P = Passenger LT = Light Truck T = Temporary Spare ST = Special Trailers
Tire Width
3-digit number that gives the approximate tire width in mm. It measures from sidewall to sidewall.
Typically, the higher the number the larger the tire.
Aspect Ratio
2-digit number that gives the approximate sidewall height. It is expressed as a % of the tire width.
The lower the ratio, the smaller the sidewall height.
Construction
R = Radial Ply B = Bias Ply
Radial tires are the industry standard and refers to the internal belts being 90 degrees to the direction of travel
Wheel Diameter
2-digit number (in inches) that indicates the tire is designed to fit on a wheel with a 16-inch diameter.
Load Index
2-digit number that indicates how much weight the tire is certified to carry at maximum safe inflation.
Speed Rating
1 letter or 1 letter/number combo which indicates the top speed at which a tire is certified under specified conditions.
DOT Codes
This assures that your tire complies with all Department of Transportation (DOT) safety standards. The next two numbers or letters are the plant code where it was manufactured. The last four numbers represent the week and year the tire was built. For example, the numbers 2212 mean the 22nd week of 2012. The other numbers in the middle are used at the manufacturer’s discretion as a code. This information is used to contact consumers if a tire defect requires a recall.
General Maintenance
Checking Tire Pressure
Be sure to check your tire pressure at least once a month and before any long road trips. Tire pressure should be checked when they are cold – driven less than a mile. Otherwise, your tires will have heated up, increasing the air pressure inside them by several pounds. You can find the OE recommended tire pressure on the placard that is usually located in the driver’s side door jam.
Under inflation causes increased stress in the sidewalls and tread area which can result in irregular wear, hydroplaning, poor fuel economy and change in vehicle handling stability.
Over inflation causes increased stress to internal materials which can result in premature failure, poor traction and change in vehicle handling/stability.
Proper Tire Pressure: Why it Matters
Driving on underinflated or overinflated tires compromises any or all of the following.
Stopping distance: Properly inflated tires maximize tread contact with the pavement, and traction along with it. Stopping with improperly inflated tires takes more distance to stop the vehicle in an emergency situation.
Ride and handling: When the tires have too much air, they’re overly rigid, which means they don’t absorb as much impact, so the car rides rougher and suspension components wear faster. An overinflated tire’s tread may crown, allowing only the center portion to contact the pavement, which decreases traction. When the pressure is too low, the ride might be softer, but the tread may not meet the road uniformly.
Fuel economy: Underinflated tires greatly reduce fuel economy.
Treadwear: Along with the traction decrease that comes with overinflation, it also causes the tread to wear more quickly in the center. Underinflation causes wear closer to the sides and allows more heat buildup, speeding wear.
Load bearing: Each tire is rated to carry a maximum amount of weight at a prescribed tire pressure. Some cars specify a higher pressure for greater loads. At best, a tire that’s underinflated for the load at hand will suffer the problems detailed above. Extra heat generated in the tire can cause it to fail even if it had held up under a lighter load.
Tire Rotation
Regular rotation helps extend the life of your tires and improve performance because each tire carries a different amount of weight, making them wear at different rates. During rotation, each tire and wheel is removed from your vehicle and moved to a different position to ensure that all tires wear evenly and last longer. Please refer to your owner’s manual for a rotation schedule and pattern specific to your vehicle. However, a good rule of thumb to avoid irregular tire wear is to rotate your tires about every 6 months or 10,000-12,000 Kms.
When tires are unbalanced, ride quality and tire life are significantly impacted. An unbalanced tire is usually detectable by vibrations in the steering wheel at higher speeds. Tires should be inspected by a professional as soon as possible to avoid excessive wear and damage.
Aligning your tires ensures that all of them are adjusted to travel in the same direction. Daily impacts such as potholes can knock your vehicle out of alignment. You should have the alignment checked if you’ve hit something substantial, you see a wear pattern developing on the shoulders of the tires and/or you notice a difference in your vehicle’s handling.INSPECT YOUR TIRES. DO NOT DRIVE ON A DAMAGED TIRE OR WHEEL.
Any time you see any damage to your tires or wheels replace with spare at once and immediately see your tire dealer. When inspecting your tires, including the spare, check your air pressures. If your pressure check indicates that one of your tires has lost pressure of two pounds or more, look for signs of penetrations, valve leakage, or wheel damage that may account for the air loss. Always look for bulges, cracks, cuts, penetrations and abnormal tire wear particularly on the edges of the tire tread which may be caused by misalignment or underinflatlon. If any such damage is found, the tire must be inspected by any tire dealer at once. Use of a damaged tire could result in sudden tire destruction. All tires will wear out faster when subjected to high speeds as well as hard cornering, rapid starts, sudden stops, frequent driving on roads which are in poor condition, and off road use. Roads with holes and rocks or other objects can damage tires and cause misalignment of your vehicle. When you drive on such roads, drive on them carefully and slowly, and before driving at normal or highway speeds, examine your tires for any damage, such as cuts or penetrations.
DO NOT OVERLOAD. DRIVING ON ANY OVERLOADED TIRE IS DANGEROUS.
The maximum load rating of your tires is marked on the tire sidewall. Do not exceed these ratings. Follow the loading instructions of the manufacturer of your vehicle and this will insure that your tires are not overloaded. Tires which are loaded beyond their maximum allowable loads for the particular application will build up excessive heat that may result in sudden tire destruction. Do not exceed the gross axle weight ratings for any axle on your vehicle. If you anticipate towing a trailer, you should see any tire dealer for advice concerning the correct size of tire and pressures. Tire size and pressures will depend upon the type and size of trailer and hitch utilized, but in no case must the maximum cold inflation pressure of tire load rating be exceeded. Check the tire placard and the owner’s manual supplied by the manufacturer of your vehicle for further recommendations on trailer towing.
STORAGE
Tires should be stored in a cool dry place indoors so that there is no danger of water collecting inside them. Serious problems occur with tube type tires when they are mounted with water trapped between the tire and the tube. Due to pressurization, the liquid can pass through the inner liner and into the casing plies. This can result in sudden lire failure. Most of the problems of this nature, encountered with tube type tires, have been due to improper storage which permitted water to enter the casing between the tire and tube prior to mounting. When tires are stored they should be stored in a cool place away from sources of heat and ozone such as hot pipes and electric motors. Be sure that surfaces of which tires are stored are clean and free from grease, gasoline or other substances which could deteriorate the rubber. Tires exposed to these materials and/or excessive heat for a prolonged period of time during storage or driving may be weakened and subject to sudden failure.
TIRE MOUNTING CAN BE DANGEROUS
Tire mounting can be dangerous and should be done by trained persons using proper tools and procedures. Your tires should be mounted on wheels which are in good, clean condition. Bent, chipped or rusted wheels may cause tire damage. Have your dealer check the size and condition of your wheels before mounting new tires. Be sure rim/Wheel manufacturer’s recommendations are followed. The inside of the tire must be free of foreign material. Old valves may leak. When new tubeless tires are mounted, have new valves of the correct type installed. Be sure that all of your valves have suitable valve caps
Driving Hazards
Hydroplaning
Hydroplaning occurs when a vehicle begins to float on top of the water on a wet road. To reduce your risk of hydroplaning, slow down on wet roads.
Three main factors contribute to hydroplaning, or the loss of traction on wet roads:
- Vehicle speed: As speed increases, wet traction is considerably reduced.
- Water depth: The deeper the water, the sooner you will lose traction, although even thin water layers can cause a loss of traction, even at low speeds.
- Tire tread depth: As your tires become worn, their ability to resist hydroplaning is reduced.
Driving on Ice And Snow
All-season tires are designed to provide higher levels of snow traction than non-all-season tires. You have all-season tires if you find the letters “M+S” molded into the sidewall near the bead. These letters mean “Mud and Snow.”
For Safe Winter Driving:
- Reduce your speed. Even good road conditions can deteriorate quickly.
- Increase your stopping distance by at least 12 times more than on dry roads. You may not always need that much distance, but when you do, you’ll be glad you were playing it safe.
- Check the condition of your tires. Worn tires provide less grip.
HIGH SPEED DRIVING CAN BE DANGEROUS
Correct inflation pressure is especially important. However, at high speeds, even with the correct inflation pressures, a road hazard, for example, is more difficult to avoid and if contact is made, has a greater chance of causing tire damage than at a lower speed. Moreover, driving at high speed reduces the reaction time available to avoid accidents and bring your vehicle to a safe stop. Never exceed the legal speed limit.
