Article > Chassis (Suspension/Steering)

How do you fix an air ride suspension that has gone flat?

By Larry Carley

If an air spring or air shock develops a leak (which most do after many years of service), the air spring or shock can’t hold pressure. It will leak and eventually go flat.
A. It depends on why the suspension went flat. Cadillac and Lincoln have used air-ride suspensions under their cars for many years. Other makes and models have air leveling suspensions that use air shocks and an onboard compressor to maintain ride height. If an air spring or air shock develops a leak (which most do after many years of service), the air spring or shock can’t hold pressure. It will leak and eventually go flat.

To make matters worse, a constant air leak at a spring, shock or air line causes the compressor to run constantly. The compressor is not designed to run constantly and sooner or later it burns out and fails from being worked to death. Consequently, if a compressor has failed, there is usually an air leak somewhere in the air ride suspension that needs to be found and fixed before a new compressor is installed.

Replacement compressors for some of these applications are hard to find, and expensive. The same goes for the air springs and air shocks. Once a vehicle is 10 or more years old, original equipment parts may no longer be available — and if no aftermarket replacement parts are available for the application (which is often the case with less common vehicles), the vehicle owner may have few repair options.

Used parts from a high-mileage vehicle in a salvage yard are risky, and new air ride suspension parts may cost more than an older vehicle is worth. The answer here would be a conversion kit that converts the original air spring or air ride suspension to a normal suspension with conventional springs and shocks or struts. Such kits are available for many of these older applications and offer an affordable alternative to replacing the original air springs, shocks or compressor.

Q. How important is ride height?

A. Ride height is the normal height at which a vehicle sits with respect to the ground when it is unloaded. Ride height is an important dimension because it can affect the caster/camber alignment of the front wheels, and the camber alignment of the rear wheels on vehicles that have an independent rear suspension.

Caster is the forward or rearward tilt of the steering axis. The caster angle affects steering effort when turning and steering return. European cars typically have a lot of caster to enhance high-speed steering stability.

Camber is the inward or outward tilt of the wheels when viewed from the front or rear. Camber affects shoulder wear on the tires, steering stability, traction and handling (especially when cornering). When ride height changes, it can alter both camber and caster — usually for the worse. Weak, sagging springs or a broken spring may change these angles so much that tire wear, steering and handling are adversely affected. A simple wheel alignment cannot correct for weak or broken springs, so new springs are needed if the original springs are not capable of maintaining the specified ride height.

Ride height is measured at specific locations on a vehicle with respect to the ground. The vehicle manufacturer indicates where ride height should be measured, and lists an acceptable range for the distance. Ride height should be checked on both sides and the front and rear of the vehicle. Alignment technicians should always measure ride height as part of a pre-alignment inspection (but they don’t always do it!). If ride height is less than specifications, the vehicle needs new springs.

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