Tire Speed Index

  • Author: OPONEO.COM

 If you are not very confident in automotive matters, and you are about to change the tires in your car, we have something for you - a portion of useful information about the tire speed index - what it is and why it is important? Read our article and learn about the risks generated by wrongly selected tires.

Tire Speed Index

Tire Speed Index

What is the Tire Speed Index?

The Tire Speed Index is the maximum permitted speed at which the car can drive with the specified tire type under the maximum load defined by the Tire Load Index. These two parameters are dependent on each other and they must be always taken into account when mounting tires in a car.
The speed index is marked on the side of the tire with letters and numbers. Any planned change of tires should be in accordance with recommendations of the car manufacturer, as stated in the car type-approval. When specifying tire parameters, the manufacturer takes into account the car's power, its weight mass and other features that affect driving safety. 

Seasonal tires and speed index

For summer tires never use tires with a speed index lower than that specified by the manufacturer.
It is different in the case of winter tires. The speed index for snow tires and the rules for its selection are defined by EU legislation (Directive 92/23/EEC). According to these regulations, winter tires may have a speed index lower than recommended by the manufacturer, but not lower than index Q (Q = 160 km/h). If the car is provided with tires of a lower speed index, then the appropriate designation should be visible to the driver.
Finally, although it is permitted, you should thoroughly consider the use of tires with a lower speed index - they may wear faster and your car may respond differently than before. To ensure safe and comfortable driving, the speed index of your tires should not be lower than the type-approved index by more than one degree.

Information on change to the tire speed index.

Information on change to the tire speed index

Each designation marked on the tire’s sidewall provides valuable guidelines that should be followed, if you are selecting new tires for your car. Proper selection of tires ensures safe and comfortable driving. The most important values that need to be taken into consideration when choosing tires include: size, load index, speed index as well as the date and place of manufacture.

What may be the consequences of using tires with an improper speed index?

  • Dangerous driving. Improperly selected tires may cause the car to drive and react differently to the driver's actions.

  • The tire may blowout causing a serious accident.

  • In case of a collision or traffic incident, the insurer may refuse to pay the insurance compensation due to improperly selected tires.

  • Loss of guarantee for the purchased product. Mounting the wrong tire type in your car voids its guarantee.

  • A police officer in the course of a routine control may charge you with a fine for using improper tires.

Indexes higher than approved? 

It is possible to mount tires with higher load and speed indices than those provided by the manufacturer. Is it worth it to exchange the tires for those that have higher indexes?

Why use tires with a higher index rating: Disadvantages of using tires with a higher index rating:
They provide increased stability of the car when driving into the wind Higher tire price
Driving is more precise, and the car responds better to the movements of the steering wheel "Stiffening of the vehicle" - reduces travel comfort
Reliable control during sports driving Higher rolling resistance, causing increased fuel consumption
Better cornering Tires with an index other than recommended, change the driving properties of the vehicle

Tables explaining markings on the tire.

Marking on the tire Speed
A1 5 km/h
A2 10 km/h
A3 15 km/h
A4 20 km/h
A5 25 km/h
A6 30 km/h
A7 35 km/h
A8 40 km/h
Marking on the tire Speed
B 50 km/h
C 60 km/h
D 65 km/h
E 70 km/h
F 80 km/h
G 90 km/h
J 100 km/h
K 110 km/h
L 120 km/h
M 130 km/h
N 140 km/h
Marking on the tire Speed?
I 150 km/h
Q 160 km/h
R 170 km/h
S 180 km/h
W 190 km/h
U 200 km/h
H 210 km/h
V 240 km/h
W 270 km/h
Y 300 km/h

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