youAll tires incorporate a code which refers to his dimensions already their capabilities. It is not a serial number written in large letters. And not some kind of barcode that identifies the product, because in fact there are always tires from different manufacturers that use the same code.
Practically all drivers know that the numbers generally allude to the tire dimensionsalthough most have some false belief which we will discuss later. And what almost nobody knows is what the final letter means, which can go From the a (accompanied by a 1) to the Y (the alphabetical order is not strict, as you will see) and for which they can back our car in the ITV.
First of all, let’s do a very quick review of what the leading digits mean. The first number is clear to everyone. In the case of the tire you see in the image above, 195 refers to the tire width measured in millimeters.
The following, which appears after a slash, is not the profile measured in millimeters, as many believe. It is actually the relationship that the profile has with respect to the width of the tire. Thus, and returning to the example of the image, 65 means that its profile is equal to 65% of the width of the tire. That is to say, that if you do the accounts it will measure 126.75 mm.
According to the R.means that it is a radial structure tire, in this case 16 inches (each inch equals 25.4 mm).
things get complicated
We come to the characters that almost no one understands: the number that follows is the maximum weight measured in kg that each tire can support (what in some catalogs comes as Load Index). And you can find yourself from the 64 of the older and smaller cars, which means that each tire can support 280 kg at the top of the load, while 126, which would allow us to load 1,700 kg per tire (for large-tonnage trucks). In this case, 91 equals 615 kg.
And now we do find the ‘cherry’ of that last letter, which many overlook when they go to order a new set of tires but which is also very important. Its about speed code. That is to say, the maximum speed that it can support without risk of the rubber suffering any damage and safely for a time of at least 10 minutes.
The codes actually start with the letter a followed by a 1, which means that it only allows you to drive at 5 km/h. And so we could tell you that there are other combinations of letters and numbers, or letters alone, that indicate improper speeds for a car today. That is why we are going to reveal to you which are the most common and the most capable, which are these:
- N 140km/h
- P 150km/h
- R 170km/h
- S 180 km/h
- T 190 km/h
- U 200km/h
- H 210km/h
- V 240 km/h
- ZR over 240 km/h
- W 270km/h
- and 300km/h
Regarding this code, we must bear in mind that it is not allowed installing a tire of a lower speed code to the one indicated in the vehicle’s technical data sheet, since it will not guarantee safety to the same extent. And, therefore, and as we have commented above, it can be the cause that the car does not pass the ITV. However, it is allowed to install a top speed codeAlthough it is always recommended to follow the indications on the file.