How to read tyres sizes for different vehicles?

BAS Tyres vehicle inspectionBAS Tyres vehicle inspection

Finding out what size tyre you need for your vehicle can be a very difficult and time consuming task. On this page we will show how you can read the tyre size of your vehicle type.
We will briefly explain in general terms how to read the tyre size. Then we will go into the vehicle-specific details of how it can be read.

The following 4 vehicle types will be covered:

  • Reading tyre sizes on trucks and trailers.
  • Reading tyre sizes of tractors and agricultural vehicles.
  • Reading tyre sizes of earth moving machines (OTR).
  • Reading tyre sizes of light commercial vehicles.
BAS Tyres employee inspects rear tyresBAS Tyres employee inspects rear tyres

Where do I find the tyre size on my tyre?

I can seem like a hard task to determate which tyre size you need for your vehicle, but it is actually quite simple.
A lot of information about a tyre is printed on the side. This side is better known as the sidewall of a tyre. Even on trucks, tractors / agricultural vehicles, large earth-movers (OTR) and light commercial vehicles like work vans, you can find this information on the sidewall.

On this sidewall you will find a string that consist of letters and numbers. With this information you can determite what tyre size you need for your application. In the following paragraph we will explain on how you can interpretend this number/letter combination.

How do I read the tyre size on my tyre?

To explain how to read the tyre size we use the following number found on the tyre sidewall: 315/70R22.5.

The first 3 digits, 315 in this case, indicate the width of the tyre in millimetres. So the tyre is 315 mm wide.
The slash "/" does not indicate anything but serves as a separator.
After the slash comes the number 70. This indicates the height of the sidewall as a percentage of the width. So the height is 70%.

The letter R indicates that this is a Radial tyre
The 2 number after the big R indicates the diameter of the rim. In this case the wheel has a diameter of 22.5 inches.

Often there is also the load rating on a tyre. This is how much load you can carry with the vehicle based on the tyre. You need to look up this number in a table to find out how much kg you are allowed to transport.

After that there is often a letter. This indicates the speed rating of the tyre. It shows the maximum speed the tyre can be driven. You can also look this up in a table.

BAS Tyres has put together the tables for the various tyres specifically for each vehicle category. For more information, you can look up the specifics on each page.

BAS Tyres employee removes tyre from a vehicleBAS Tyres employee removes tyre from a vehicle

Most common tyre sizes, load index and speed index

As described above, it is important to choose the right load index and speed index when selecting a tyre.
BAS Tyres has specified this per vehicle and the tables can be found by clicking on the buttons below.

Truck tyres load index and speed index

Trucks have specific load capacity rules. It is therefore very important to choose the right tyre that corresponds to the load capacity indicated by the manufacturer of the truck or trailer.
Periodic inspections check whether the tyres correspond to the load capacity specified by the manufacturer. If this number is not correct, the entire truck or trailer will be rejected.

By clicking on the button below, you will find the table containing the load index, speed index and other important data.

Truck tyres load / speed indexTruck tyres load / speed index

Earth-moving tyres load index and speed index

Tyres for large earthmoving machines are different from truck tyres. With these tyres, it is important to choose the right load index. Based on this load index, the maximum speed of the machine is also determined.
Furthermore, the pattern of the tyres is very important. The letter E indicates that the tyre is suitable for Earthmoving vehicles, G stands for Graders, and L for Loader.

For more information click on the button below

large earthmoving vehicles tyre speed/ load indexlarge earthmoving vehicles tyre speed/ load index

Van tyres load index and speed index

The reading of tyre sizes for light commercial vehicles is almost identical to the process of reading a truck tyre.

For this product group too, BAS Tyres has collected all important figures in tables.

Light commercial vehicle tyre load / speed indexLight commercial vehicle tyre load / speed index

Agriculteral tyres load index and speed index

For tractors, it is important to choose the right tyre. Tractors are used for different applications; some tractors drive more on the road than others. Some tractors will only be used in the field and need more traction than those that are driven on the road.

BAS Tyres has also put the most important information in an overview for you.

Agricultural load/speed tyre indexAgricultural load/speed tyre index
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