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-   -   Load Range/Ply Rating Identification (http://www.fordtruckclub.net/forum/showthread.php?t=6237)

HawaiianF150 January 8th, 2012 01:25 AM

Load Range/Ply Rating Identification
 
Load Range/Ply Rating Identification

The load range or ply rating branded on a tire's sidewall helps identify how much load the tire is designed to carry at its industry specified pressure. Passenger tires feature named load ranges while light truck tires use load ranges that ascend in alphabetical order (letters further along in the alphabet identify stronger tires that can withstand higher inflation pressures and carry heavier loads).

Before load ranges were adopted, ply ratings and/or the actual number of carcass plies were used to identify the relative strength with higher numeric ratings or plies identifying tires featuring stronger, heavier duty constructions.

Today's load range/ply ratings do not count the actual number of body ply layers used to make up the tire's internal structure, but indicate an equivalent strength compared to early bias ply tires.

Most radial passenger tires have one or two body plies, and light truck tires, even those with heavy-duty ratings (10-, 12- or 14-ply rated), actually have only two or three fabric plies, or one steel body ply. In all cases, when changing tire sizes or converting from one type of size to another, it is important to confirm that the Load Index in the tire's Service Description of the new tire is equal to or greater than the Load Index of the original tire.

Light Truck Tires
Since light truck tires are often available in multiple load ranges; the appropriate load range is identified immediately following the size's rim diameter.

LT-Metric, LT-Flotation and LT-Numeric tires are branded with their load range (Load Range E or LRE) or their ply rating (10 Ply Rated) on their sidewalls and list their appropriate load range letter in their descriptions as LT245/75R-16 E, 7.50R-15 D or 31x10.50R-15 C.

Load Range -Ply Rating - Markings - Max Load Pressure

B - 4 - B - 35 psi (240 kPa)
C - 6 - C - 50 psi (350 kPa)
D - 8 - D - 65 psi (450 kPa)
E - 10 - E - 80 psi (550 kPa)
E - 10- E - 80 psi (550 kPa)***
F - 12 - F - 95 psi (650 kPa)***
***Selected large LT sizes are designed with reduced maximum load pressures

Speed Rating

Speed Rating tells you the maximum speed capability of a tire. Often speed ratings are matched to the top speed capability of the vehicle the tire is going on. For example, a tire with an H-speed rating has a maximum speed capability of 130 mph or 210 km/h.

Speed Rating - Max MPH - Typical Usage

M - 81 mph
N - 87 mph - Spare Tires
P - 93 mph
Q 99 mph - Winter Tires
R 106 mph - Truck Tires
S 112 mph - Cars and Minivans
T 118 mph - Cars and Minivans
U 124 mph - Sport-Performance Cars
V 149 mph - Sport-Performance Cars, High-Performance Cars
W 168 mph - Ultra High-Performance Cars
Y 186 mph - Ultra High-Performance Cars

UTQG stands for Uniform Tire Quality Grading, a rating system developed by the U.S. Department of Transportation to provide consumers with information to help them purchase tires based on their relative tread wear, traction and temperature capabilities.

Traction grades indicate the wet traction of a tire under a controlled test. A tire with an "AA" rating offers outstanding traction in wet conditions. Traction Grades: AA, A, B

Temperature grades indicate the ability of the tire to withstand and dissipate destructive heat. A tire with a higher temperature grade is able to operate at higher speeds.
Temperature grades: A, B, C

Tread wear grades are based on standardized government tests to help predict the expected tread wear of a tire. For example, a tire with a tread wear grade of 200 should last twice as long as a tire with a tread wear grade of 100.


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