Load and speed index of truck tyres

Load index and speed index for truck tyres

The load index is the official code that indicates how much weight a single tyre may carry at the correct tyre pressure. This value is always shown on the tyre sidewall, directly next to the speed index.

Never use a tyre with a lower load index than the vehicle’s original specification. Exceeding the permitted load can lead to excessive deformation, heat build-up and, in extreme cases, tyre failure.

Especially in countries where trucks are routinely more heavily loaded, such as Germany and Poland, the correct load index is crucial for safety and tyre life. The load index table below shows exactly which load capacity corresponds to each index value.

When fitting tyres, always check that the tyres on the same axle have an identical load index. A higher load index on one side can never compensate for a load index that is too low on the other side.

Tyre pressure and load capacity

A tyre’s load capacity is only valid at the correct tyre pressure. Pressure that is too low causes additional deformation, heat build-up and higher fuel consumption. Pressure that is too high reduces the contact area and grip, particularly in wet conditions.

Correct tyre pressure offers four major benefits: maximum load capacity, even wear, lower fuel consumption and improved driving safety. Regular pressure checks help prevent damage to the casing and extend tyre life.

Transport operators in the Benelux often drive with varying loads and therefore benefit particularly from using the correct tyre pressures. For international journeys in the DACH region, maintaining stable tyre pressure is important to protect the vehicle combination against heat stress at higher speeds.

Load index when replacing truck tyres

When replacing truck tyres, the load index of the new tyre must be at least equal to that of the original tyre. A higher load index is permitted; a lower load index is not.

This is because the load index applies to each individual tyre. Two tyres on the same axle must always have the same load index to prevent imbalance and uneven loading.

A tyre with a much higher load index on one side does not compensate for a tyre with a lower index on the other side. This can lead to cracking, instability and tread deformation.

In practical situations — such as distribution vehicles in the Netherlands or heavily loaded tractor units in Eastern Europe — incorrect load index selection is one of the most common causes of premature tyre damage.

What is the speed index of a truck tyre?

The speed index is the code that indicates the maximum speed a tyre can safely handle. This speed is determined by the manufacturer through laboratory testing, during which the tyre runs against a metal drum at increasing speeds.

The speed index is shown next to the load index on the tyre sidewall. Each letter or letter/number combination represents a specific maximum speed, such as A8 (40 km/h), F (80 km/h) or T (190 km/h).

Even tyres that are rarely used on the road are assigned an official speed index. The specified maximum speed only applies to tyres that are undamaged, not overloaded and correctly inflated.

Repaired tyres generally do not retain their original speed index, because the quality of the repair can affect heat management within the tyre.

Safety and speed index in practice

Respecting the speed index is important to prevent overheating, cracking and possible casing failure. Trucks operating at higher average speeds, such as those used for international transport, are particularly susceptible to heat build-up if the speed rating is insufficient.

Tyre pressure also plays an important role. An underinflated tyre deforms more and heats up faster, reducing its effective maximum speed.

In regions such as Germany, where some motorway sections have no general speed limit, many transport operators deliberately choose tyres with higher speed ratings. However, the operating application remains the key consideration. An urban distribution vehicle, for example, does not require a high speed index, but may require a higher load index.

The combination must always match the application, speed and load.

Load index and speed index tables

The table below contains the complete list of official load index values and their corresponding maximum load capacities. Beneath this, you will find the complete speed index table with all speed ratings from A1 through to ZR.

These tables are based on international standards and apply to all truck and trailer tyres used in Europe. Use these tables when selecting new tyres, modifying vehicles or making technical comparisons between different brands.

The combination of load index and speed index determines which tyre is suitable for a particular vehicle type and application. If in doubt, always consult the vehicle documentation or ask our experts for advice.

Tyre load index

Speedindex (SI)

Frequently asked questions (FAQ)

1. What does the load index on a truck tyre mean?
The load index indicates how much weight a single tyre can safely carry at the correct tyre pressure.

2. Where can I find the speed index?
The speed index is always shown next to the load index on the tyre sidewall.

3. Can I use tyres with different load indexes on the same axle?
No. Both tyres on the same axle must always have the same load index.

4. Does the speed index also apply to repaired tyres?
No. The original speed index is not guaranteed for repaired tyres.

5. What happens if tyre pressure is too low?
Underinflation increases heat build-up, wear and the risk of tyre failure.