Load Index

The load index is a standardised measurement used globally to ensure that tyres are matched correctly to a vehicle's weight requirements – thus acting as a safety threshold that prevents structural failure under stress. It is a numerical code that represents the maximum weight capacity each tyre can safely support.

Understanding what the load index on tyres means is crucial for vehicle maintenance, as it ensures that you don’t accidentally compromise safety by installing tyres with insufficient load capacity.

The load index is an assigned numerical value – ranging from 0 to 279 – that corresponds to the maximum load-carrying capacity of a single tyre. It is important to note that the number itself (e.g., 91) is not the weight in kilograms or pounds, but a code that refers to a specific weight in a standardised load index chart.

Exceeding the load capacity of your tyres is a leading cause of tyre failure. Overloaded tyres build up excessive heat, which can lead to structural damage or a sudden blowout, especially at high speeds or in hot climates.

Locating the load index is straightforward once you know where to look on the tyre’s sidewall. It is part of the standardised service description that includes both the load capacity and the speed rating.

Reading the sidewall markings: On the sidewall of any modern tyre, you will see a string of numbers and letters. For example, in the sequence 205/55R16 91V, “91” is the load index. This is the number you must match or exceed when purchasing replacement tyres.

While often used interchangeably, there is a technical distinction. The load index is the numerical code (e.g. 91) printed on the sidewall, whereas the load rating – or load-carrying capacity – refers to the actual weight in pounds or kilograms that the tyre is rated to carry. Essentially, the load index is the shorthand symbol, and the load rating is the real-world performance value it represents.

While these terms are always grouped together, they serve different purposes. The load index tells you how much weight the tyre can carry, while the speed index (the letter following the number, like "V") indicates the maximum speed the tyre can safely maintain under that specific load.

This table provides a quick reference for converting the numerical load index into actual weight capacities (per tyre). Use these values to ensure your tyres are capable of supporting your vehicle's fully loaded weight.

The weight-carrying capacity of a tyre is not static. It depends heavily on the air pressure inside. Without the correct inflation, even a high-index tyre cannot perform its job safely.

A tyre's load index rating is only valid if the tyre is inflated to its maximum cold inflation pressure. For daily driving, you should follow the vehicle manufacturer's recommended PSI, but when hauling heavy loads, you may need to increase the pressure – just be sure never to exceed the maximum limit.

Air carries the weight, not the rubber. If your tyres are under-inflated while carrying a heavy load, the sidewalls flex excessively, generating internal heat that can lead to a catastrophic tyre failure.

When the time comes to replace your tyres, you have some flexibility, but there are strict safety limits you must respect. You should always use caution when deviating from the original equipment (OE) specs.

Upgrading to a higher index: It is perfectly safe – and often beneficial – to install tyres with a higher load index than the ones that originally came with your vehicle. This can provide a greater safety margin and better stability when the vehicle is fully loaded.

Why you should never go lower than the OEM specs: You should never install tyres with a lower load index than what the vehicle manufacturer specifies. Doing so can result in poor handling, increased tyre wear, insurance complications, and a significantly higher risk of blowouts.

The tyre load index is a vital safety specification that ensures your tyres can handle your vehicle's weight and cargo. Choosing the correct index prevents overheating and catastrophic tyre failure while maintaining the structural integrity of your tyre's footprint.

Always remember that while you can safely upgrade to a higher load rating, you must never go below the manufacturer's original specifications. By pairing the right load index with proper inflation pressure, you ensure a safer, more efficient, and more reliable driving experience.