Adjustable suspension

Adjustable suspensions provide a number of remarkable advantages for automakers. For starters, the suspensions can be adjusted to provide a smooth ride for luxury and comfort oriented vehicles, or they can be tuned to provide responsive and controlled handling. An adjustable suspension can save automakers the trouble of making an array of changes to their conventional suspension setups in an effort to deliver these favorable attributes. The most common forms of adjustable suspension are hydraulic suspensions and air suspensions.

Hydraulic Suspension

A hydraulic suspension employs the use of a pressurized fluid inside of a suspension cylinder to produce resistance and control suspension movement. In addition to dampening and movement control, hydraulic suspensions can also provide ride height correction as well as suspension height control.

The majority of hydraulic suspensions found on automobiles are usually in the form of the hydropneumatic suspension. The hydropneumatic suspension was developed by Citroen and used on the French automaker`s vehicles. Mercedes-Benz, Rolls-Royce and countless other automakers have also use this type of suspension under license. The hydropneumatic suspension utilizes several cylinders filled with nitrogen gas as a spring medium, with specially developed LHM mineral oil acting against the gas cylinder. Through this method, a vehicle fitted with a hydropneumatic suspension can enjoy superior ride quality as well as excellent ride leveling.

Lowriders utilize custom-built hydraulic suspensions that allow the driver to change the suspension height at all four corners by toggling a series of controls. These units rely on a series of hydraulic pumps along with a small bank of batteries to produce specific motions from the vehicle. Some of these suspensions even allow the vehicle to hop several inches off the ground.

Air Suspension

While hydraulic and hydropneumatic suspensions have their advantages, they also have several faults, one of the biggest being overall cost of developing such a system for use on an automobile and the cost of keeping one in excellent condition. As a result, Ford and other American automobile manufacturers elected to use adjustable suspensions that rely on compressed air.

Air suspensions work on similar principles as a hydraulic suspension, except with different methods. A bellow filled with pressurized air acts as a spring, providing much of the dampening capabilities as a hydraulic suspension. An electric or engine driven air compressor provides the pressurized air that is required to keep the car at the proper height. Air suspensions not only provide a relatively smooth ride quality, but they also provide a level ride height at all times, in most cases.

Air suspensions are commonly found on luxury automobiles and they`re also commonplace in the commercial trucking industry. These suspensions are often used in place of conventional steel springs, although many vehicles utilize supplementary suspension components to control other aspects of body motion.

Just as hydraulic suspensions have their drawbacks, so do air suspensions. For starters, vehicles equipped with air suspensions will eventually settle to the ground if the vehicle is not started for an extended period or if the air compressor is not allowed to run. Also, the bellows can deteriorate over time, leaving microscopic cracks that could allow air to escape. Many vehicles have "bump stops" incorporated into their suspension, thereby preventing the vehicle from sinking completely onto its wheels or shock towers.

Cost Comparison

Hydraulic suspensions offer excellent ride and handling attributes, but these systems are quite costly to purchase, install and maintain. Given the nature of pressurized hydraulic fluids and the need to keep this fluid contained inside vessels that are designed to withstand high pressures, the cost of maintaining a hydraulic suspension can easily outweigh the benefits of having one first place.

On the other hand, air suspensions offer a cheaper alternative to hydraulic suspensions. There are no special fluids, high-pressure lines or special-purpose containers needed for air suspensions. The only items of concern in regards to maintenance are the bellows and air compressor. Aftermarket air suspension systems are also much cheaper to purchase and easier to install.

If you`re looking to retrofit your vehicle with an adjustable suspension, it`s ultimately up to you to decide which type of suspension to install on your vehicle. If you`re in the market for vehicle that is already fitted with an adjustable suspension, the cost of maintenance and parts may be an issue if you plan on purchasing an older vehicle fitted with a hydraulic or air suspension. Torquecars.com features a wealth of information on these and other types of adjustable suspensions, along with information on other common automotive issues.