OBI WAN
11-12-04, 04:12 PM
Tire Size
The tire size is written on the tire’s sidewall.
P indicates a passenger (car-type) tire. Other options would be no P indicating metric sizing (essentially the same as P-sizing, which has its heritage in Europe) or LT for light truck. LT truck tires are designed for heavier loads and more rugged service conditions.
Width of the tire, in millimeters. The higher the number the wider the tire.
Aspect ratio — The height of the sidewall section compared to the width of the tire. Example: — If this number was a 50, then the tire section is half as tall as it is wide. Short sidewalls deliver crisp handling. Tall sidewalls give a smoother ride. For a specific tire width, the smaller this number, the shorter the sidewall.
Construction — R indicates radial construction. Unless you specify the other option, bias (which would have a D [diagonal] or B [belted bias] in this position instead of an R), you are purchasing a radial tire.
Wheel Size Designation — This indicates the distance across the “doughnut hole†of a tire, in simple terms. You must match wheel diameter and tire diameter. For example, a 15-inch diameter tire must only be mounted on a 15-inch diameter rim. A tire with a 15 size designation will not work on a 14" wheel, and vice versa. Improperly matching of wheel and tire size can cause serious injury or death during installation.
Service Description — Includes the load index (a number) and a speed symbol (a letter). About load index, remember: Keep the number the same as or greater than the original tires’ load index. That number stands for a specific weight-carrying capability. Key is that the higher the number, the greater load-carrying capacity. So keep the number the same or higher, because your tires are matched to the weight of your car. Never choose a tire with a lower load-carrying capacity than the original equipment tire size.
Uniform Tire Quality Grading (UTQG)
The Uniform Tire Quality Grading (UTQG) is a system developed by the Department of Transportation which helps consumers compare tires in the areas of treadwear traction and temperature. Here’s an example: a tire with a UTQG of 300 AB. The 300 is treadwear, which represents the tire’s comparative wear when measured against the government-mandated tire which is rated at 100. So this tire wore three times longer than the control tire. Because of variations in operating conditions, the treadwear grade cannot be used to predict actual wear out mileage; it can be used to predict the relative wear rate of tires with different UTQG wear rates. Traction and temperature are graded A (superior), B (good) or C (average). Traction indicates the level of grip the tire possesses.
Temperature rating deals with the tire’s ability to disperse built-up heat. Heat causes rubber to deteriorate over time, so dispersing heat increases tire life.
Each tire manufacturer determines UTQG ratings for their products. Realize that UTQGs are more accurate when comparing tires within the same line versus tires from two different makers.
Speed Ratings
The speed-rating system in use today was developed in Europe to categorize tires developed for specific vehicle speed requirements.
Rating symbol- Speed in MPH Maximum
B-31
C-37
D-40
E-43
F-50
G-56
J-63
K-68
L-75
M-81
N-87
P-93
Q-99
R-106
S-112
T-118
U-124
H-130
V-15-
W-169
Y-188
ZR-150+
Although a tire may be speed rated, we do not endorse the operation of any vehicle in an unsafe or unlawful manner. Furthermore, tire speed ratings do not imply that a vehicle can be safely driven at the maximum speed for which the tire is rated, particularly under adverse road and weather conditions or if the vehicle has unusual characteristics. Speed ratings are based on laboratory tests which relate to performance on the road, but are not applicable if tires are underinflated, overloaded, worn out, damaged or altered. The load index is an assigned number that corresponds with the load-carrying capacity of a tire.
The following is current information regarding speed-rated tires. Please note that many of today's vehicles are equipped with speed-rated tires. It is NOT recommended that tires on these vehicles be replaced with tires which exhibit a lower speed rating than those specified by the vehicle manufacturer.
Safety Rules for Selection, Mixing, Repairing, Retreading or Alteration of Speed-Rated Tires
It is important for the safety of the consumer that the following safety rules be followed in the selection, mixing and servicing of speed-rated tires.
Selection
When replacement of tires is desired, consult the placard (normally located on the door frame or glove box door) or the owner's manual for correct size. If the tires shown on the vehicle placard do not have speed ratings, the appropriate size tire with any speed rating may be applied, if desired. When the placard tire size nomenclature contains a speed symbol, for example P205/60HR15, the replacement tire must have the same or higher speed rating symbol if the speed capability of the vehicle is to be maintained. IF THE REPLACEMENT TIRE IS NOT SPEED RATED, OR HAS A LOWER SPEED RATING THAN INDICATED ON THE VEHICLE PLACARD, THE SPEED CAPABILITY OF THE VEHICLE IS LIMITED BY THE SPEED CAPABILITY OF THE REPLACEMENT TIRE. A Cooper-produced, non-speed-rated tire's maximum speed is 85 mph (137 km/h).
For the safety of the consumer, a dealer must advise the consumer whenever replacement tires are purchased which lower the speed capability of the vehicle and a Safety Warning/Consumer Advisory Form must be filled out by the dealer and signed by the consumer.
Dealers should follow the recommendations contained in Rubber Manufacturers' Association (RMA) publications for other considerations in the selection of replacement tires.
Mixing
Be sure to follow RMA rules for tire mixing as shown on the "Replacement Guide for Passenger Car Tires" or "Tire Replacement Guide for Light Trucks" wall charts. IF TIRES OF DIFFERENT SPEED RATINGS ARE MOUNTED ON A VEHICLE, THE TIRE WITH THE LOWEST SPEED RATING WILL LIMIT PERMISSIBLE TIRE RELATED VEHICLE SPEED. This must be explained to the consumer and a Safety-Warning/Consumer Advisory Form filled out by you and signed by the consumer.
If any replacement tire is not speed rated, the speed capability of the vehicle is limited by the maximum speed of that tire. 65MPH should be it until its known what it can handle.
The tire size is written on the tire’s sidewall.
P indicates a passenger (car-type) tire. Other options would be no P indicating metric sizing (essentially the same as P-sizing, which has its heritage in Europe) or LT for light truck. LT truck tires are designed for heavier loads and more rugged service conditions.
Width of the tire, in millimeters. The higher the number the wider the tire.
Aspect ratio — The height of the sidewall section compared to the width of the tire. Example: — If this number was a 50, then the tire section is half as tall as it is wide. Short sidewalls deliver crisp handling. Tall sidewalls give a smoother ride. For a specific tire width, the smaller this number, the shorter the sidewall.
Construction — R indicates radial construction. Unless you specify the other option, bias (which would have a D [diagonal] or B [belted bias] in this position instead of an R), you are purchasing a radial tire.
Wheel Size Designation — This indicates the distance across the “doughnut hole†of a tire, in simple terms. You must match wheel diameter and tire diameter. For example, a 15-inch diameter tire must only be mounted on a 15-inch diameter rim. A tire with a 15 size designation will not work on a 14" wheel, and vice versa. Improperly matching of wheel and tire size can cause serious injury or death during installation.
Service Description — Includes the load index (a number) and a speed symbol (a letter). About load index, remember: Keep the number the same as or greater than the original tires’ load index. That number stands for a specific weight-carrying capability. Key is that the higher the number, the greater load-carrying capacity. So keep the number the same or higher, because your tires are matched to the weight of your car. Never choose a tire with a lower load-carrying capacity than the original equipment tire size.
Uniform Tire Quality Grading (UTQG)
The Uniform Tire Quality Grading (UTQG) is a system developed by the Department of Transportation which helps consumers compare tires in the areas of treadwear traction and temperature. Here’s an example: a tire with a UTQG of 300 AB. The 300 is treadwear, which represents the tire’s comparative wear when measured against the government-mandated tire which is rated at 100. So this tire wore three times longer than the control tire. Because of variations in operating conditions, the treadwear grade cannot be used to predict actual wear out mileage; it can be used to predict the relative wear rate of tires with different UTQG wear rates. Traction and temperature are graded A (superior), B (good) or C (average). Traction indicates the level of grip the tire possesses.
Temperature rating deals with the tire’s ability to disperse built-up heat. Heat causes rubber to deteriorate over time, so dispersing heat increases tire life.
Each tire manufacturer determines UTQG ratings for their products. Realize that UTQGs are more accurate when comparing tires within the same line versus tires from two different makers.
Speed Ratings
The speed-rating system in use today was developed in Europe to categorize tires developed for specific vehicle speed requirements.
Rating symbol- Speed in MPH Maximum
B-31
C-37
D-40
E-43
F-50
G-56
J-63
K-68
L-75
M-81
N-87
P-93
Q-99
R-106
S-112
T-118
U-124
H-130
V-15-
W-169
Y-188
ZR-150+
Although a tire may be speed rated, we do not endorse the operation of any vehicle in an unsafe or unlawful manner. Furthermore, tire speed ratings do not imply that a vehicle can be safely driven at the maximum speed for which the tire is rated, particularly under adverse road and weather conditions or if the vehicle has unusual characteristics. Speed ratings are based on laboratory tests which relate to performance on the road, but are not applicable if tires are underinflated, overloaded, worn out, damaged or altered. The load index is an assigned number that corresponds with the load-carrying capacity of a tire.
The following is current information regarding speed-rated tires. Please note that many of today's vehicles are equipped with speed-rated tires. It is NOT recommended that tires on these vehicles be replaced with tires which exhibit a lower speed rating than those specified by the vehicle manufacturer.
Safety Rules for Selection, Mixing, Repairing, Retreading or Alteration of Speed-Rated Tires
It is important for the safety of the consumer that the following safety rules be followed in the selection, mixing and servicing of speed-rated tires.
Selection
When replacement of tires is desired, consult the placard (normally located on the door frame or glove box door) or the owner's manual for correct size. If the tires shown on the vehicle placard do not have speed ratings, the appropriate size tire with any speed rating may be applied, if desired. When the placard tire size nomenclature contains a speed symbol, for example P205/60HR15, the replacement tire must have the same or higher speed rating symbol if the speed capability of the vehicle is to be maintained. IF THE REPLACEMENT TIRE IS NOT SPEED RATED, OR HAS A LOWER SPEED RATING THAN INDICATED ON THE VEHICLE PLACARD, THE SPEED CAPABILITY OF THE VEHICLE IS LIMITED BY THE SPEED CAPABILITY OF THE REPLACEMENT TIRE. A Cooper-produced, non-speed-rated tire's maximum speed is 85 mph (137 km/h).
For the safety of the consumer, a dealer must advise the consumer whenever replacement tires are purchased which lower the speed capability of the vehicle and a Safety Warning/Consumer Advisory Form must be filled out by the dealer and signed by the consumer.
Dealers should follow the recommendations contained in Rubber Manufacturers' Association (RMA) publications for other considerations in the selection of replacement tires.
Mixing
Be sure to follow RMA rules for tire mixing as shown on the "Replacement Guide for Passenger Car Tires" or "Tire Replacement Guide for Light Trucks" wall charts. IF TIRES OF DIFFERENT SPEED RATINGS ARE MOUNTED ON A VEHICLE, THE TIRE WITH THE LOWEST SPEED RATING WILL LIMIT PERMISSIBLE TIRE RELATED VEHICLE SPEED. This must be explained to the consumer and a Safety-Warning/Consumer Advisory Form filled out by you and signed by the consumer.
If any replacement tire is not speed rated, the speed capability of the vehicle is limited by the maximum speed of that tire. 65MPH should be it until its known what it can handle.