Using a P195/60R15 87S tire size as our example, the 87S at the end of the size represents the tire’s service description. A service description identifies the tire’s load index and speed rating. Service Descriptions are required on all speed rated (except for Z-speed rated) tires manufactured since 1991.
The first two digits (87S) represent the tire’s load index and are followed by a single letter (87S) identifying the tire’s speed rating.
Load Index
P195/60R15 87S - The load index (87) is the tire size’s assigned numerical value used to compare relative load carrying capabilities. In the case of our example the 87 identifies the tires ability to carry approximately 1,201 pounds.
The higher the tire’s load index number, the greater its load carrying capacity.
89 = 1,279 pounds
88 = 1,235 pounds
87 = 1,201 pounds
86 = 1,168 pounds
85 = 1,135 pounds
A tire with a higher load index than that of the original equipment tire indicates an increase in load capacity. A tire with a load index equal to that of the original equipment tire indicates an equivalent load capacity. A tire with a lower load index than the original equipment tire indicates the tire does not equal the load capacity of the original.
Typically, the load indexes of the tires used on passenger cars and light trucks range from 70 to 110. Load Index Pounds Kilograms
Load Index Pounds Kilograms
71 761 345 91 1356 615
72 783 355 92 1389 630
73 805 365 93 1433 650
74 827 375 94 1477 670
75 853 387 95 1521 690
76 882 400 96 1565 710
77 908 412 97 1609 730
78 937 425 98 1653 750
79 963 437 99 1709 775
80 992 450 100 1764 800
81 1019 462 101 1819 825
82 1047 475 102 1874 850
83 1074 487 103 1929 875
84 1102 500 104 1984 900
85 1135 515 105 2039 925
86 1168 530 106 2094 950
87 1201 545 107 2149 975
88 1235 560 108 2205 1000
89 1279 580 109 2271 1030
90 1323 600 110 2337 1060
Speed Rating
P195/60R15 87S - The tire speed rating (S) is the maximum speed for which the tire is rated. For example, the “S” rating identifies speeds up to 112 mph (180 km/h).
It is important to note that speed ratings only apply to tires that have not been damaged, altered, under-inflated or overloaded. Additionally, most tire manufacturers maintain that a tire that has been cut or punctured no longer retains the tire manufacturer’s original speed rating, even after being repaired.
In Europe, where selected highways do not have speed limits and high speed driving is permitted, speed ratings were established to match the speed capability of tires with the top speed capabilities of the vehicles to which they are applied. Speed ratings are established in kilometers per hour and subsequently converted to miles per hour (which explains why speed ratings appear established at “odd” mile per hour increments). Despite the tire manufacturer’s ability to manufacturer tires capable of high speeds, none of them recommend the use of their products in excess of legal speed limits.
Speed ratings are based on laboratory tests where the tire is pressed (to reflect its required load) against a large diameter metal drum and run at ever increasing speeds (in 6.2 mph steps in 10 minute increments) until the tire’s required speed has been met.
Speed Rating - Miles/Hour - Kilometers/Hour - Typical Use N=87 MPH, 140km/h, Spare Tires U=124 MPH, 200km/h
P=93 MPH, 150km/h H=130 MPH, 210km/h, Sport Sedans
Q=99 MPH, 160km/h, Winter, LT Tires V=149 MPH, 240km/h, Sports Cars
R=106 MPH, 170km/h, LT Tires Z=149 MPH, 240km/h and over, Sports Cars
S=112 MPH, 180km/h W=168 MPH, 270km/h, Exotic Sport Cars
T=118 MPH, 190km/h Y=186 MPH, 300km/h, Exotic Sport Cars
*Today, the Z-speed rating is the only speed rating that is still branded “within” the tire size, as in P225/50ZR16. All other speed ratings are shown in the tire’s service description.
When Z-speed rated tires were first introduced, they were thought to reflect the highest speed rating that would ever be required. Since that time the automotive industry has found it necessary to add W- and Y-speed ratings (indicated in the tire’s service description) to identify the tires that meet the needs of new vehicles that have extremely high, top speed capabilities.
Miles/Hour Kilometers/Hour
P225/50ZR16 149+ 240+
P225/50ZR16 91W 168 270
P225/50ZR16 91Y 186 300
While all Z-speed rated tires are capable of speeds of 149 mph and above, prior to the W- and Y-speed ratings were identified in the service, how far above 149 mph was not identified.
Prior to 1991, the most popular speed ratings were “S,” “H” and “V.” However, while the speed capabilities of S- and H-rated tires still indicate the same speeds as before, the V-speed rating has been modified. Previously a V-speed rated tire with the “V” branded “within” the tire size indicated that the tire was capable of 130+ miles per hour as indicated below:
Miles/Hour Kilometers/Hour
P225/50SR16 112 180
P225/50HR16 130 210
P225/50VR16 130+ 210+
Today’s new V-speed rated tires are always identified in the tires service description:
Miles/Hour Kilometers/Hour
P225/50R16 91V 149 240
