Understanding Tyre Load Index

Tyre load index — the quick answer

The load index is the number just before the speed-rating letter — the ‘91’ in 205/55R16 91V — and it sets the maximum weight each tyre can carry: 91 equals 615 kg. Fit a lower index than your car’s handbook specifies and the tyre can fail under load; you can go higher, never lower. How to read the index and choose correctly is below.

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The load index system uses numbers from approximately 62 to 126 for passenger car tyres, with each number corresponding to a specific maximum load in kilograms. The relationship is not linear, meaning you cannot simply calculate the load from the index number. Instead you need to consult a load index table. This guide provides a comprehensive table, explains how load index relates to your vehicle requirements, and covers the legal and safety implications of getting it wrong.

The Complete Load Index Table

The following table shows the most commonly encountered load index values for passenger cars, SUVs and light commercial vehicles. Each tyre on your vehicle must have a load index that matches or exceeds the specification in your vehicle handbook.

To calculate the total load capacity of your vehicle tyres, multiply the single tyre load capacity by four. For example four tyres with load index 91 support a total of 2,460 kg which must exceed the vehicle maximum laden weight including passengers and cargo.

How to Find Your Required Load Index

Your vehicle required minimum load index is listed in several places. Check the tyre information placard on the driver door jamb which shows the original equipment tyre size including load index. The vehicle owner manual also specifies the minimum load index. The tyres currently fitted to your vehicle show their load index on the sidewall which you can cross-reference.

When replacing tyres, always match or exceed the minimum load index specified by the vehicle manufacturer. Never fit a tyre with a lower load index even if the overall size matches. For a complete explanation of all tyre sidewall markings including load index and speed rating, see our guide on how to read tyre size numbers.

Standard vs Extra Load Tyres

Tyres are manufactured in two load classifications: standard (also called SL) and extra load (marked XL, EL, or RF for reinforced). For the same tyre size, the XL version will have a higher load index, typically 3 to 4 points higher than the standard version, because its reinforced construction allows it to operate at higher inflation pressures.

For example a 225/45R17 tyre might have a load index of 91 in standard form and 94 in XL form. The standard version carries 615 kg per tyre at its maximum rated pressure of 2.5 bar while the XL version carries 670 kg at a maximum of 2.9 bar.

If your vehicle was originally fitted with XL tyres, you must replace them with XL tyres of the same or higher load index. Fitting standard tyres where XL tyres are specified will result in an inadequate load capacity even if the tyre size appears identical. This is a common and dangerous mistake.

The Relationship Between Load Index and Pressure

A tyre load index rating is based on the tyre being inflated to its maximum rated pressure. At lower pressures the maximum safe load is proportionally reduced. This is why correct tyre inflation is so important for both safety and tyre longevity.

Vehicle manufacturers specify tyre pressures for normal load and fully laden conditions. The fully laden pressure is higher to compensate for the additional weight. Always adjust your tyre pressure according to load conditions especially before long motorway journeys with a full car and luggage. Our comprehensive tyre pressure guide covers this topic in detail including how to find your correct pressures and when to adjust them.

Underinflation is particularly dangerous from a load perspective because it reduces the tyre effective load capacity while simultaneously increasing operating temperature. This combination accelerates tyre degradation and increases the risk of sudden failure. Overloading an underinflated tyre is one of the most common causes of motorway blowouts.

Vehicle Weight and Load Capacity Calculations

Understanding how your vehicle weight relates to tyre load capacity requires knowing three key figures. The kerb weight is the weight of the vehicle empty with a full tank of fuel. The gross vehicle weight is the maximum permissible weight including all occupants and cargo. The difference between these two figures is your maximum payload.

For a typical family saloon with a kerb weight of 1,500 kg and gross vehicle weight of 2,000 kg, the payload capacity is 500 kg. With four passengers at 75 kg each (300 kg) you have 200 kg remaining for luggage. Four tyres with load index 91 support 2,460 kg total which exceeds the 2,000 kg gross vehicle weight with a comfortable safety margin.

For SUVs and larger vehicles the calculations become more critical. A large SUV with a gross vehicle weight of 2,800 kg requires tyres with a load index of at least 100 per tyre (800 kg times 4 equals 3,200 kg) to maintain an adequate safety margin. Always ensure the total tyre load capacity exceeds the vehicle gross weight.

Legal Requirements for Load Index

In most countries it is illegal to fit tyres with a load index lower than the vehicle manufacturer specification. In Germany this is checked during the TUV inspection and non-compliant tyres will result in a failed inspection. In the United Kingdom the MOT test checks tyre condition including suitability for the vehicle and an incorrect load index can be grounds for failure.

France and Italy also require tyres to meet manufacturer specifications including load index. Police roadside checks in many European countries include tyre compliance and fines for non-compliant tyres vary from EUR 90 to EUR 350 depending on the jurisdiction.

Beyond legal requirements, using incorrect load index tyres can void your vehicle insurance. If an accident investigation reveals that your tyres were inadequate for the vehicle, the insurance company may reduce or deny your claim entirely.

Load Index for Different Vehicle Types

Different vehicle types require different load index ranges due to their varying weights and use cases.

Performance versions of vehicles may require higher load indices than standard models due to increased vehicle weight from performance components. Always check your specific vehicle specification rather than assuming one model matches another.

Common Mistakes to Avoid

The most common load index mistake is fitting standard tyres where XL tyres are required. This happens frequently when drivers shop by size alone without checking the XL designation. A 225/45R17 91V and a 225/45R17 94V XL are the same physical size but have very different load capacities.

Another common error is ignoring the load index when buying budget tyres online. Some budget tyre listings show only the size and speed rating, omitting the load index. Always verify the load index before purchasing and compare it to your vehicle requirement.

A third mistake is failing to account for additional weight when modifying a vehicle. Aftermarket accessories such as bull bars, roof racks, heavy audio systems, or towing equipment increase the vehicle weight. If these additions push the laden weight above the original tyre load capacity you may need to upgrade to higher load index tyres.

Towing and Load Index

When towing a caravan or trailer, the load on the rear tyres increases significantly due to the towbar nose weight. A typical caravan nose weight of 75 to 100 kg is added directly to the rear axle, increasing the load on each rear tyre by approximately 40 to 50 kg. Ensure your rear tyres have sufficient load capacity to handle this additional weight.

Many vehicle manufacturers specify higher tyre pressures for towing. Check your owner manual for towing tyre pressure recommendations and adjust accordingly before each towing journey. In Germany trailer tyres must be no older than 6 years, as discussed in our tyre age guide.

Conclusion

The tyre load index may seem like a minor specification but it directly affects your safety on the road. Always match or exceed the load index specified by your vehicle manufacturer, understand the difference between standard and XL tyres, maintain correct inflation pressure for your load conditions, and never overload your vehicle beyond its tyre capacity. These simple steps prevent dangerous tyre failures and keep you legal in every country you drive through. For more tyre knowledge explore our guides on tyre size markings and EU tyre label ratings.