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How to read a truck tyre?

Finding the right truck tyre size can be quite a challenging task. On this page, we explain how to determine the correct tire size and how to interpret this size. This way, you know exactly which tire to buy for your truck!

On this page, we also explain what the most common tyre sizes are, what the load index of the tyre is, and how to find out the speed rating of the tyre.

View all our truck tyres

Where can I find the tyre size of my truck?

The tyre size of a truck tyre is located on the side of the tyre. This side is also called the ‘sidewall’ of a tyre. On this side, there is a sequence of information consisting of a combination of letters and numbers. In the image below, you can see the tyre size of a light commercial vehicle. You can find the tyre size of a truck in the same place.

BAS Group top view Disassembled truck

How to read the tyre size of a truck?

A truck tyre consists of different elements; the truck tyre width, height, and the inch size of the tyre.
We found the following number-letter combination on the sidewall of a random truck tyre in our warehouse. On the sidewall of the tyre, the following number/letter combination is: 315/70R22.5 156/150L
Based on this combination, we will explain how this number should be interpreted.

The aspects of the truck tyre explained briefly

A truck tyre has different characteristics. To explain all the features simply, we use the number/letter combination mentioned above in the paragraph: 315/70R22.5 156/150L

The first 3 digits: 315 indicate the width of the tyre.
The / is a separator and has no further meaning.
The number 70 shows the tyre height of the tyre.
The letter R indicates that it is a Radial tyre.
22.5 shows the inch size of the tyre.
The numbers 156/150 show the load index of the tyre.
The letter L shows the speed index of the tyre. This letter corresponds to a certain speed. This speed can be read in a table. We have this table at the bottom of this article.

The width of the truck tyre

The width of the tyre is indicated by the first three digits in the tyre size. In our example, the entire letter combination is: 315 /70R22.5 156/150L. The first 3 digits are in this case 315. The width of the truck tyre is therefore 315 mm.

The truck tyre height

The tyre height is indicated after the slash ( / ) in the tyre size. Let's take our example again: 315 /70R22.5 156/150L. The tyre height in this case is the number 70.

The tyre height is always expressed as a percentage of the tyre width. The tyre height is therefore 70% of 315 mm (315 is the width of the tyre we described above). This percentage does not need to be calculated.

The truck tyre size and radial tyres

In the example: 315 /70R22.5 156/150L, the letter R indicates that it is a radial tyre. The radial tyre (indication R) is the most common tyre. In the past, the diagonal tyre (indication D) was the standard in the industry, but it has been replaced by the radial tyre.

The inch size of truck tyres

Trucks, trailers, and semi-trailers can have the following inch sizes 22.5 inches, 20 inches, 19.5 inches, or 17.5 inches. The inch size is always mentioned at the end of the tyre size after the letter R.

Engine racks BAS Parts & Tyres

Load index and speed index

Behind the rim size is always a number and a letter. In our example, 315 /70R22.5 156/150L, it concerns the numbers: 156/150L. The number 156/150 The number indicates the load index of a tyre. The number 156/150 corresponds to a specific number that indicates how much the tyre can be loaded. Tyres with a load index of 156 can, for example, be loaded with 4000 kg.

Load index of a truck or trailer tyre.

The load index stands for the maximum load capacity of a tyre at the ideal tyre pressure. It is important that the tyres are not overloaded.

During the periodic inspection (APK or TÜV for example), this is checked and enforced. If you do not have the correct load index on your vehicle, the inspection authority will reject your vehicle. The load index is indicated by codes on the tyre.

The code for the load index is always found on the side of the tyre.

Table with the load index of a truck or trailer tyre
Loadindex KG's Loadindex KG's
115 1215 139 2430
116 1250 140 2500
117 1285 141 2575
118 1320 142 2650
119 1360 143 2725
120 1400 144 2800
121 1450 145 2900
122 1500 146 3000
123 550 147 3075
124 1600 148 3150
125 1650 149 3250
126 1700 150 3350
127 1750 151 3450
128 1800 152 3550
129 1850 153 3650
130 1900 154 3750
131 1950 155 3875
132 2000 156 4000
133 2060 157 4125
134 2120 158 4250
135 2180 159 4375
136 2240 160 4500
137 2300 161 4625
138 2360 162 4750

Snelheidsindex van vrachtwagen- en trailerbanden

De snelheidsindex van een band verwijst naar de maximale snelheid waarmee met de band mag worden gereden. De snelheidsindex wordt aangeduid met een letter na de loadindex. Bijvoorbeeld, voor een 315/70R22.5 156/150L vrachtwagenband is de belastings- en snelheidsindex 156/150L, 156/150 is de belastingsindex en de letter L staat voor de snelheidsindex van maximaal 120 kilometer per uur.

Speed symbol Maximum speed (km/h) Speed symbol Maximum speed (km/h)
A1 5 K 110
A2 10 L 120
A3 15 M 130
A4 20 N 140
A5 25 P 150
A6 30 Q 160
A7 35 R 170
A8 40 S 180
B 50 T 190
C 60 U