People often ask about air suspension, and then ask “well what actually is an airbag?”.

Well in terms of air suspension an air bag is a rubber bag which holds air (no surprise there) and which would more helpfully be known as an air spring. The Bag replaces the spring on the car, but on the whole all the rest of the suspension and the dampers (shock absorbers) are left in place and as-is.

When changing from conventional suspension to air suspension, you are (massive simplification here) changing from fixed metal springs to variable rate air springs.

The advantage of the airbag is a side effect of the variable rate - less air = less height, and up a limit - more air = more height. Thus we can run really low cars, that are now practical to drive and can clear speed bumps, and pot holes.

All we really need is an air source on board and a controller and we can lift or drop the car whilst driving.

There are many types and sizes of air bag, but the most common fitted to modified cars, are Firestone or Firestone copies. For the most part I don’t use Firestone bags - they have fabulous quality control (they always work, and are always well made - no faulty ones), but are pretty low spec (max pressure 100 psi), and the spring rate varies too much. This means when the car is low it has a poor ride, and when it is high it also has a poor ride, and is only acceptable when around the driving height.

In reality this is not too much of an issue, but there are better alternatives, especially given that basic compressors now deliver 150 or 200 psi. Firestone also classify them as assister springs - i.e. they are designed for vans to assist the standard spring, and not as the sole spring on a car.

We use the Quantum Sport bag. This is a revolution in the airbag market. It takes higher pressure, has a stiffer deflated rate, which leads to more consistent spring rates, therefore it drives better either high or low.

This is our bag of choice - it handles almost as well as a “coil spring conversion”, rides almost as well as the original suspension, and lifts and drops at the touch of a button - this is the nearest to perfect that air has even got!! If you don’t tell the passenger you are running air then they don’t know - its that good.