How to read a truck tyre?

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.

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 In the past, the diagonal tyre (indication D) was the standard in the industry, but it has been replaced by the radial tyre.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.

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