Tires are constructed to suit different drivers and vehicles. Tires are as unique as the vehicles they'll be put on; however, all tires possess similarities in order to offer optimal performance and to meet safety standards. One similarity that all tires possess is load sensitivity. Load sensitivity is a direct result of the weight limit a tire's manufacturer has assigned to it. This weight limit is called the load index for passenger tires and load range for light truck tires. It determines how much weight a tire can safely carry.
Tires are designed to work in a set of four to support the weight of the vehicle plus the weight of additional cargo or passengers. Load sensitivity describes how a tire's performance is affected by the weight it carries.
What is Load Sensitivity?
Load sensitivity measures how much weight a tire can safely carry while it's in use. Imagine the tire being squeezed between the weight of the vehicle above it and the road below it. Just like anything else, a tire can be squeezed too hard. This is load sensitivity. It's one of the key variables in determining how a tire will behave while you drive on it.
The weight of the vehicle, passengers, and cargo affects all aspects of tire performance. Fuel efficiency changes with load sensitivity. So do important maneuvering characteristics like relaxation length — how long it takes the tires to grip the road and turn the vehicle after you've turned your steering wheel. If you've read our article on relaxation length, you may see how load sensitivity changes this important performance characteristic. Speed wobble is also a phenomenon that can occur at high speeds depending on the tire's load sensitivity, regardless of driving maneuvers. A tire with increased load sensitivity cannot maintain designed specifics and stability when driving at high speeds. You run the risk of losing control of your vehicle if it's too sensitive to its load.
What Directly Affects the Load Sensitivity?
The load index or range is printed on every tire sold in the United States. It's a letter in the code on the tire's sidewall. The letter represents the tire's safe weight range according to its manufacturer. You should only load your vehicle with the amount of weight authorized by the automaker. The tire load range and the automaker recommendation will be different numbers since tires can fit on more than one vehicle. Always check your vehicle owner's manual for the right number.
Excessive load sensitivity develops when vehicles carry more weight than what is recommended. This can cause multiple problems for a tire. For starters, overloading prevents vehicles from responding as designed or as a driver anticipates. This can cause unsafe driving or traffic accidents.
Consistently overloading a vehicle can cause tires to deteriorate too quickly. Problems with treadwear and tire stability caused by excessive load sensitivity will shorten the amount of time you can safely use your tires. When you overload tires, the tread can become particularly worn on the outer edges (shoulders) due to the excessive mass that's applied to the tire. Overloading can also cause tires to overheat from the inside and then blow out.
To say that appropriately loading the tires on a vehicle is important is an understatement. In fact, tire overload is one of the most common reasons for tire failure. To avoid excessive load sensitivity, always use tires that are approved by your vehicle's manufacturer for your make and model.