How to calculate tire equivalences and measurements


When we want to change the tires of our vehicle, either because they are worn out or because the wheel has been punctured, we have to take into account a series of aspects, since not just any type of tire will do. What we must keep in mind is nothing more than the equivalences and measurements of the tires’

How to calculate tire equivalences and measurements

What are tire equivalencies?

Tire equivalences help us to know if the tire we want to purchase is suitable for our vehicle in terms of measurements, both for the good functionality of the car and for not having subsequent problems when passing the ITV.

According to Order 3191/2002 of the BOE (Official State Gazette), it is not necessary to homologate new tires if they meet a series of characteristics:

  • Outside Diameter – This should be roughly the same size. However, a small variation of 3% is accepted.
  • Load capacity: this must be equal to or greater.
  • Speed ​​Category Code – Must be equal to or greater. Only for M+S tires is a slightly lower level allowed.
  • Mounting rim: the mounting rim profile must correspond to that of our tires.

How to know the size of the tires

Knowing the measurements of your original tires is easier than you think. All the information you need is on the side of the wheel, there you will find:

  • The width of the wheel.
  • The tire profile.
  • The load capacity of the wheel.
  • The speed of the tire.

How to read tire size

Whatever your tire, the pattern will always be the same: XXX / XX A XX XXA. In this case, the X represents a number, and the A letter. Suppose that the measurements of our tire are 220 / 40 R 10 92V:

  • 220: This indicates the width of the tire. The measurement is in millimeters.
  • 40: this figure is the profile of the tire, that is, its height. In this case it is a percentage, that is, the height of the tire is 44%.
  • R: in this case, it means that the tire has been built radially.
  • 10: this indicates the size of our rim. Here it is indicated in inches.
  • 92V: This is a code that is equivalent to the load capacity and the maximum speed that it can support.

Tire Equivalence Calculator

The simplest way to calculate the equivalences and measurements of the original tires with the new ones that we want to look for is to go to an online tire equivalence calculator, like the one we offer you here.

In the tire equivalence calculators, you only have to enter the measurements of your original tires and the measurements of the tires you want to purchase. The calculator will automatically tell you if those new wheels are suitable for your vehicle or not. Therefore, it is ideal to do this step before purchasing new tires.

How do I know what tires I can put on my car?

Now that you know how to calculate tire equivalencies and measurements, you may be wondering what type of tires are right for your vehicle. In photo we give you the answer in these two articles:

  • How to choose tires for an SUV.
  • How to choose car tires.


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