The load rating for each Air Lift air spring is a combination of two things: the pressure and the diameter.
Obviously, the higher the pressure, the greater the load the air spring will carry. The diameter is important because that is the factor that determines the air springs load support at a given pressure. This means that the larger the diameter, the larger the surface area to which the pressure is applied.
For example: a 6 inch diameter air spring will have a surface area of 28 1/4 square inches on the diameter. Apply 100 lbs. of pressure, and the result would be 2,825 lbs. of force. (100 psi x 28.25 sq inches = 2,825 lbs.)
Taking a closer look, bellows style air springs change diameter as they extend and compress. The spring will be at its greatest diameter when compressed and smallest diameter when fully extended. Because of the diameter change, the air springs ability to support a load will change as the air bag compresses and expands. The load support will increase as the air spring compresses and vice versa. This is a feature designed to create a build up of spring rate when hitting a bump or adding more load.
Sleeve style air springs change diameter very little throughout its designed normal operating range and the load supporting ability will remain relatively constant at a given pressure. However, if the sleeve is compressed below its normal operating range and the rubber rolls down and bottoms out on the mounting surface, the diameter will begin to grow. This will cause an increase in the spring rate. This is not a problem unless the rubber is being damaged from something that it is rolling down into.
All Air Lift air spring kits have a maximum load rating and are achieved only under certain conditions, which involve the air pressure in the spring, and the length that it is mounted. This means that the air bag will support the maximum weight while near full compression and at maximum pressure and will support the least weight at its maximum height.
The maximum load rating on each Air Lift air spring kit are as follows:*
* Never exceed manufacturer’s recommended Gross Vehicle Weight Rating.