Tire Rack.com

How to Read Speed Rating, Load Index & Service Descriptions


Lea esta página en español

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 IndexPoundsKilograms
Load IndexPoundsKilograms
71761345911356615
72783355921389630
73805365931433650
74827 375941477670
75853387951521690
76882400961565710
77908412971609730
78937425981653750
79963437991709775
809924501001764800
8110194621011819825
8210474751021874850
8310744871031929875
8411025001041984900
8511355151052039925
8611685301062094950
8712015451072149975
88123556010822051000
89127958010922711030
90132360011023371060

Speed Rating

In Germany some 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 capability 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 "unusual" 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. The maximum operating speed of a vehicle must be limited to the lowest speed rated tire on the vehicle.

Speed ratings are based on laboratory tests where the tire is pressed against a large diameter metal drum to reflect its appropriate load, and run at ever increasing speeds (in 6.2 mph steps in 10 minute increments) until the tire's required speed has been met.

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 because the tire manufacturer can't control the quality of the repair.

Over the years, tire speed rating symbols have been marked on tires in any of three ways shown in the following examples:

225/50SR16225/50SR16 89Sor 225/50R16 89S

Each of these was an acceptable method of identifying speed ratings.

Early tires had their speed rating symbol shown "within" the tire size, such as 225/50SR16. Tires using this type of branding were not to have been produced after 1991.

225/50SR16112 mph, 180 km/h
225/50HR16130, 210 km/h
225/50VR16in excess of 130 mph, 210 km/h

Beginning in 1991, the speed symbol denoting a fixed maximum speed capability of new tires must be shown only in the speed rating portion of the tire's service description, such as 225/50R16 89S. The most common tire speed rating symbols, maximum speeds and typical applications are shown below:

L75 mph120 km/hOff-Road & Light Truck Tires
M81 mph130 km/hTemporary Spare Tires
N87 mph140km/h
P93 mph150 km/h
Q99 mph160 km/hStudless & Studdable Winter Tires
R106 mph170 km/hH.D. Light Truck Tires
S112 mph180 km/hFamily Sedans & Vans
T118 mph190 km/hFamily Sedans & Vans
U124 mph200 km/h
H130 mph210 km/hSport Sedans & Coupes
V149 mph240 km/hSport Sedans, Coupes & Sports Cars

When Z-speed rated tires were first introduced, they were thought to reflect the highest tire speed rating that would ever be required, in excess of 240 km/h or 149 mph. While Z-speed rated tires are capable of speeds in excess of 149 mph, how far above 149 mph was not identified. That ultimately caused the automotive industry to add W- and Y-speed ratings to identify the tires that meet the needs of new vehicles that have extremely high top-speed capabilities.

W168 mph270 km/hExotic Sports Cars
Y186 mph300 km/hExotic Sports Cars

While a Z-speed rating still often appears in the tire size designation of these tires, such as 225/50ZR16 91W, the Z in the size signifies a maximum speed capability in excess of 149 mph, 240 km/h; the W in the service description indicates the tire's 168 mph, 270 km/h maximum speed.

225/50ZR16in excess of 149 mph, 240 km/h
205/45ZR17 88W168 mph, 270 km/h
285/35ZR19 99Y186 mph, 300 km/h

Most recently, when the Y-speed rating indicated in a service description is enclosed in parentheses, such as 285/35ZR19 (99Y), the top speed of the tire has been tested in excess of 186 mph, 300 km/h indicated by the service description as shown below:

285/35ZR19 99Y186 mph, 300 km/h
285/35ZR19 (99Y)in excess of 186 mph, 300 km/h

As vehicles have increased their top speeds into Autobahn-only ranges, the tire speed ratings have evolved to better identify the tires capability, allowing drivers to match the speed of their tires with the top speed of their vehicle.

Most Popular Links

Air Pressure - Correct, Underinflated and Overinflated
Air Pressure vs. Dry Performance
Air Pressure vs. Wet Performance
Air Pressure, Temperature Fluctuations
Air Pressure/Load Adjustment for High Speed Driving
Air Pressure: When and How to Set
Alignment
Breaking In Your Tires
Calculating Tire Dimensions
Checking Tire Inflation Pressure
Determining the Age of a Tire
Diameter Comparison of Light Truck Tire Sizes
How Do I Compare Price vs. Value?
How to Read Speed Rating, Load Index & Service Descriptions
Load Range/Ply Rating Identification
Match Mounting to Enhance Tire & Wheel Uniformity
Load Reduction of Euro- and P-Metric Tires on Light Trucks
Measuring Tire Tread Depth with a Coin
Mounting and Balancing
P-Metric and Euro Metric Tire Sizing
Run-Flat Tires
Selecting the Right Tires
Sidewall Markings
Specific Mileage Warranties
The Plus Concept
Tire & Wheel Owner's Manual
Tire & Wheel Package Installation Instructions
Tire & Wheel Package Ride Uniformity Confirmation
Tire Pressure Monitoring Systems
Tire Rotation
Tire Size Conversion Chart
Tire Size Information
Tire Warranties
Uniform Tire Quality Grade (UTQG) Standards
Where to Install New Pairs of Tires?


JOIN US
GET OUR EMAILS

Want to stay on the inside track?
Sign up for our emails today!