General function of tires for all types of vehicles
1. Weight-bearing
Air pressure and tire construction are important factors to carry and sustain the weight of vehicles.
2. Absorb shocks
Air pressure and tire construction reduces initial road vibrations and shocks before being muted again by the suspension .
3. Delivering power from the engine
Tires serve to deliver power from the engine to move the vehicle and also provides traction and braking performance .
4. Translating steering wheel movement
Tires are very important in controlling the direction of the vehicle, which will determine the maneuvering capability and stability in driving.

  Understand tire size
Tires have its 'language' to communicate in the form of a series of numbers and letters to indicating data specification, brand and type. It is universal and has been agreed by all tire manufacturers worldwide.

Here are the meanings of these codes:
1. Tire width (in mm)
2. A tire's aspect ratio is the dimensional relationship of the tire's section height to section width, expressed as a percentage.
3. Diameter of wheel (in inches)
4. Load Index
5. Speed Index

  UTQG (Uniform Tire Quality Grades) Rating
The UTQG (Uniform Tire Quality Grades) rating is a labeling requirement by the U.S Department of Transportation for all tire manufacturers. The label of UTQG represents a tire's Treadwear, Traction and Temperature resistance. Traction and temperature resistance ratings are specific performance levels, while treadwear ratings are assigned by manufacturers following tests conducted and are reliable when comparing tires of the same brand.

The UTQG rating comprises of 3 components.
Treadwear
The treadwear grade indicates the wear rate of a tire and is a comparative rating based on test conducted by tire manufacturers. The grades are not an indication of actual mileage, but can be used as a relative comparison. For example, a grading of 400 should last twice as long as a tire graded 200, given similar driving conditions in the same brand.

Traction
Traction rating is an indication of a tire's ability to stop on wet pavement. The braking distance is indicated by ratings of "AA" (highest braking ability), "A", "B" and "C". Traction rating only indicates straight line wet braking and does not indicate wet cornering abilities of the tire.

Temperature
Temperature resistance rating indicates the tire's ability to withstand heat. It is graded according to a properly inflated and not overloaded tire. It is graded from "C", being the lowest, to "B" and "A" ratings.
  Understand Load Index and Speed Rating
The Speed index is an assigned letter ranging from J to Z that corresponds to the reference maximum speed at the associated load index. Refer to the load index and speed rating tables below.

These two elements put together are called the service description and are mutually dependent. The table below gives the load index and the speed symbol with their corresponding value.

  Load Index (Symbol and maximum load in Lbs & Kg)
LI Lbs Kgs LI Lbs Kgs LI Lbs Kg LI Lbs Kg
71
72
73
74
75
76
77
78
79
80
761
783
805
827
853
882
908
937
963
992
345
355
365
375
387
400
412
425
437
450
81
82
83
84
85
86
87
88
89
90
1019
1047
1074
1102
1135
1168
1201
1235
1279
1323
462
475
487
500
515
530
545
560
580
600
91
92
93
94
95
96
97
98
99
100
1356
1389
1433
1477
1521
1565
1609
1653
1709
1764
615
630
650
670
690
710
730
750
775
800
101
102
103
104
105
106
107
108
109
110
1819
1874
1929
1984
2039
2094
2149
2205
2271
2337
825
850
875
900
925
950
975
1000
1030
1060


  Speed Rating (symbol and maximum speed in MpH & KmH)
J K L M N P Q R S T H V W Y
MpH
62
68
75
81
87
93
100
106
113
118
130
150
168
188
KmH
100
110
120
130
140
150
160
170
180
190
210
240
270
300
Note: A "ZR" may appear for tires having a maximum speed capability above 240km/h (150 mph)



 

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