What is the tire load index?
4 Answers
Tire load index, also known as tire load rating, refers to the numerical code indicating the maximum load capacity that a tire can bear when operating at the speed specified by its speed symbol under standard usage conditions. The load index of tires ranges from 70 to 109, corresponding to maximum load capacities of 335-1030kg. Exceeding the tire's maximum load capacity won't cause immediate damage, but prolonged overloading will lead to tire fatigue, shorten the tire's service life, and may even result in a blowout in severe cases. Additional information: The load index and maximum load capacity of each tire are molded on the tire sidewall. For example, in the tire specification 195/65-R15-91V, the load index is 91, which corresponds to a maximum load capacity (single tire) of 615 kilograms.
The tire load index essentially indicates the maximum weight a single tire can bear, much like how we should carry a backpack within our capacity. This value is usually engraved on the tire sidewall as a two-digit number, for example, 91 represents 615 kilograms. When selecting tires, the load index must be higher than the vehicle's actual load; otherwise, it may lead to sidewall deformation, overheating, or even a blowout, which is especially dangerous when driving on highways in summer. Once, when I helped a friend change tires, I noticed his off-road vehicle often carried heavy cargo, but the original tires had a load index of only 95. I recommended upgrading to off-road-specific tires with a load index of 102 to match the vehicle's curb weight and maximum load capacity. Remember, the load index and speed rating should be considered together—don't just opt for cheaper tires with a lower load index. Safety should always come first.
The load index, simply put, indicates a tire's load-bearing capacity. The higher the number, the greater the load it can handle. Common passenger car tires typically have load indices between 90-100, roughly equivalent to 600-800 kg per tire. But many overlook a crucial point: the combined weight of the vehicle, passengers, and luggage must not exceed the total load index of all four tires! I learned this the hard way when overloaded my pickup truck - the tires bulged and deformed quickly. In reality, the load index affects not just durability but also braking performance and fuel efficiency. Chronic overloading accelerates tread wear. When replacing tires, don't just focus on size; check your owner's manual for manufacturer recommendations - SUVs or MPVs often require higher indices.
The numbers in that string of code on the tire sidewall represent the load index, which together with the speed rating indicated by letters determine the tire's load-carrying capacity. For example, the 91 in 225/45R17 91V stands for a load capacity of 615 kg. This index is tested under standard temperature and pressure conditions - insufficient tire pressure during actual use can reduce effective load capacity by over 20%. We recommend checking tire pressure monthly, especially before long trips with full loads. Some owners install larger rims but use tires with lower load indexes - this is like carrying heavy loads while wearing small shoes, potentially causing tire bulges at best or high-speed loss of control at worst. Original equipment specifications are safest; when replacing tires, maintain at least the same load index.
