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Tire Service Description, Load Index & Speed Rating Explained

There are many factors that contribute to how your car performs when you drive it. However, few factors have as direct an influence on how your car actually handles the road as your tires. Because of this, it's definitely in your best interest to have a good understanding of your tires' capabilities and more importantly, their limitations. Driving too fast or overloading your vehicle can have a negative impact on your tires. That's where tire service descriptions come in. Service descriptions let you know your tires' load limit and speed rating.

About Tire Service Description

Tires are built to withstand more abuse than most of the other parts of your car. After all, your tires are the only part of your car that actually comes into contact with the roads you drive on. Therefore, it's important that you understand them as much as possible. Fitting a vehicle with tires that have a load rating lower than recommended or loading up your car with too much weight can strain your tires, causing them to wear out faster or even potentially blow out.

By the same token, driving your car too fast can also put more strain on your tires than they can withstand. So, just how much weight is too much weight and how fast is too fast? It varies depending on the tires. Your tires' weight and speed limits are indicated by the tire service description; a short code located on the sidewalls of your tires.

This short code, which consists of a two or three-digit number along with a single letter, designates just how much weight your tires are capable of carrying safely and the maximum speed the tires are designed for.

Understanding Tire Service Descriptions

The numbers in a tire service description designate the tire's load index. The number doesn't indicate the actual weight the tire is capable of supporting. Rather, it's a code that corresponds with an actual weight. You can decode this number with a load index chart.

The higher a specific tire's load rating is, the greater its capacity for carrying loads. Typical load indexes on passenger cars and light trucks range from 70-110, which as you can see below, indicate weight from 739-2337 pounds.

Load IndexMax Weight (lbs)
70739
71761
72783
73805
74827
75852
76882
77908
78937
79963
80992
811019
821047
831074
841102
851135
861168
871201
881235
891279
901323
Load IndexMax Weight (lbs)
911356
921389
931433
941477
951521
961565
971609
981653
991709
1001764
1011819
1021874
1031929
1041984
1052039
1062094
1072149
1082205
1092271
1102337

The letter that follows this number designates a tire's maximum speed rating, providing the tire hasn't been damaged, overburdened, under-inflated, or altered in any way. While a given tire's speed rating may be higher than the speed limit, tire manufacturers strongly advise that their products only be used within the legal speed limit.

This table illustrates speed ratings for most tires intended for passenger use.

Speed RatingMax Speed (mph)
L75
M81
N87
P93
Q99
R106
S112
T124
H130
V149
W168
Y186

Speed ratings are first determined in kilometers per hour and then converted to mph, which is why the intervals are somewhat irregular.

If you have questions about your tire service description, you can always consult an automaker-certified service adviser any time you bring your vehicle into the dealership for service. Retailer locations maintain close relationships with vehicle and tire manufacturers. These close relationships enable them to provide you the best possible advice in relation to service descriptions for your tires.

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