Tyre Speed Index

  • Author: OPONEO.CO.UK

 

If you are not very confident in automotive matters and you are about to change the tyres on your car, then we have something for you –  a portion of useful information about tire speed index (what it is and why it is important). Read our article and learn about the risks asscoiated with wrongly selected tyres.

 



Tire Speed Index

Tire Speed Index 

What is the Tyre Speed Index?

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

Seasonal tyres and speed index. 

For summer tyres, tires with a speed index lower than that specified by the manufacturer should never be used.
It is different in the case of  winter tyres. The speed index for snow tyres and rules for its selection are defined by EU legislation (Directive 92/23/EEC). According to these regulations, winter tyres may have their speed index lower than recommended by the manufacturer, but not lower than index Q (Q = 160 km/h). If the car is provided with tyres 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 tyres with a lower speed index. They may wear faster and your car may respond differently than before. To ensure a safe and comfortable drive, the speed index of your tyres should not be lower than the type-approved index by more than one degree.


Changing the speed index of your tires.

Changing the speed index of your tires.

Each designation marked on the tire sidewall provides valuable guidelines that should be followed, when selecting new tyres for your car. The proper selection of tyres ensures safe and comfortable driving. The most important values that need to be taken into consideration when choosing tyres include size, load index, speed index, date and place of manufacture.

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

●      Dangerous driving. Improperly selected tyres may cause a different response of the car to the driver's steering action.
●      The tyre may blow causing a serious accident.
●      In the case of a collision or traffic incident, the insurer may refuse to pay insurance based on a poor selection of tyres.
●      Loss of guarantee for the purchased product. Installing the wrong type of tyres on your car makes their guarantee void.
●      A police officer in the course of a routine control may issue a fine for having the wrong tyres fitted.

Indexes higher than approved? 

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


Why use tyres with an overstated index: Disadvantages of using tyres with a higher load index:
They provide increased stability of the car while driving into the wind The higher the price of tyres
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 a sporty drive Higher rolling resistance, causing increased fuel consumption
Better cornering Tyres with an index other than recommended change the driving properties of the vehicle

Tables explaining markings on the tyre. 

Marking on the tyre 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 tyre 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 tyre 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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