Tire speed index

When buying tires online, there are several variables to consider in order to make a choice that is as thoughtful as possible. 

In this regard, the speed index is also very important, a parameter to which you should always refer to avoid bringing home tires that are not suitable for the type of vehicle you own.

Tire speed index: general aspects

The code that indicates the speed of the tires is a parameter that must never be neglected in order to tackle each journey in complete safety.

More specifically, this index is represented by a letter and, as the name suggests, it is equivalent to the maximum speed that a tire can tolerate while driving.

The letters that distinguish the index start from L and arrive at Y. Each one refers to a speed. For example, the R corresponds to 170 km / h, while the V corresponds to 240 km / h.

The motorist can rely on the appropriate official table to find out the correspondences between letters and permitted speed indices.

Where is the speed code for the tires?

To find out the maximum speed code of your tires you need to do a quick and simple check. In fact, it is sufficient to observe the letter indicated on the shoulder of the tire and then go back to the maximum speed it can withstand.

When, for example, the letter W is read on the shoulder, it means that the tire can travel at a legally permitted speed of 270 km / h. In the case of the letter P, on the other hand, the speed is lowered to 150 Km / h.

How to calculate the tire speed code

All the maximum speeds are reported by the manufacturers after having carried out careful laboratory tests on the various types of tires. The tires are tested at 10 km / h. The speed is then gradually increased every 10 laps and until the desired one is reached.

Ultimately the code is assigned once it is ascertained that the tire can sustain certain speeds during the test. The latter also takes into account any loads.

As already mentioned, the codes are classified from the letter L to Y but there are anomalies, because in the control phase some car companies have increased the maximum speed of the vehicles and therefore more adequate parameters have been introduced.

What exactly does the tire speed code refer to?

Many motorists wonder if the index marked by the letter on the shoulder of the tire refers only to speed. In reality, this parameter is also closely linked to the comfort that is perceived while driving.

The speed index, more specifically, is attributable to the cornering set-up and tread wear. This means that when a tire has a higher speed code it consequently ensures greater grip and more force when stopping.

All this provided that the temperatures are not low, otherwise there may be lower performance, as well as a not very resistant tread.

This explains why tires with indices marked with the letters V, Z, W and Y are generally recommended for those vehicles that ensure better performance during the summer season, that is, when temperatures are warmer.

It should also be noted that it is allowed to increase the speed index of one's tires in order to maximize performance.

However, it is not allowed to do the reverse, that is to reduce the index without lowering the maximum speed of the vehicle, so as to adapt it to that of the lower code.

Can tires with different speed codes be combined?

Serious and reliable companies that deal with online tire sales strongly advise against combining tires with different speed ratings, as this could significantly compromise comfort and safety on the road.

Drivers who intend to make this combination anyway will need to be very cautious and pay close attention. In fact, it is necessary to make sure that the tires with the lowest index are mounted on the front axle, but not only.

It is also necessary that the means of rear-wheel drive, all-wheel drive or rear-wheel drive, because in this way possible oversteer problems can be prevented. 

When buying new tires online it is important to adapt them to your vehicle, so you should never exceed the maximum speed limit.

Tire speed code: other things to know

The offer of tires online is quite vast today and when you shop, the comparison of the speed index proves to be crucial in order not to make any errors in judgment. So you don't just have to consider the price factor.

The general rule, which must always be followed, is to mount tires of the same type, which therefore have the same dimensions and the same speed index on all four wheels.