Class Act

The nature of hot rodders has always been to try to improve the performance of virtually every aspect of the automobile. Often those improvements in performance have been the result of utilizing parts from here, there, and yon and adapting them from one application to another. Certainly, when it comes to suspension systems, coilovers, air springs, and of course the Mustang II independent front suspensions (along with all its derivatives) are prime examples. But the most outrageous example of borrowed suspension technology may be right around the corner.

Recently, we became aware of CLASS, or the Compressible Liquid Adaptive Suspension System, from LiquidSpring Technologies (LST). Developed in the early '80s, LST then introduced a system that uses a compressible liquid as a spring/damping medium for off-road mining trucks. In the '90s the system was adapted to lighter-weight vehicles and received a variety of patents, and within the last few years a system has been created for Ford F-250 trucks and E-450 chassis. And while it would certainly stretch the limits of adapting from one application to another, it's possible that a version of this suspension system could become a reality for street rods.

Unique in virtually all regards, CLASS uses hydraulics for the suspension system and eliminates springs, shock absorbers, and stabilizer bars, as the fluid becomes the spring, damping, and roll-control medium.

In addition to those normal suspension functions, CLASS also provides unparalleled flexibility by virtue of ride and height adjustability, both of which are controlled by a panel in the passenger compartment.

The CLASS is made up of a strut, one mounted at each wheel (they look like a large shock absorber with hydraulic lines and an electrical connection), that serves as the spring, shock, and antiroll bar. A central power supply with a pump and reservoir supplies hydraulic pressure to each strut via a device called a corner manifold. These units each incorporate solenoids that control fill, dump, and rate-dampening valves that adjust the volume of fluid in the strut, which in-turn establishes the spring rate, damping rate, and resistance to body roll. Each strut also requires a small tank, or canister, for supplemental fluid.

As might be expected, there are a number of sensors used with this system, including those for ride height, steering position, brake application, vehicle speed, and body inclination. The data from these sensors is supplied to the controller, which calculates the appropriate vehicle attitude (ride height), stiffness (spring rate), and damping (shock rate) based on the baseline performance statistics that have been programmed into it. The controller then sends the appropriate signals to the corner manifolds to activate the fill and dump valves to control ride height; to adjust corner stiffness to control roll and pitch; to modify corner damping to control wheel hop; and to turn the pump on and off to raise or lower the vehicle.

To allow the system to be tuned for a variety of applications, the controller can be reprogrammed to fit a particular vehicle's needs. However, the parameters are such that the controller still gives the driver the option to select from three ride modes: comfort for a softer, more compliant ride with reduced roll stiffness; normal for "improved-from-stock ride and handling;" and sport for a firmer ride and increased load stiffness. In addition to ride setting, the controller also allows the ride height to be adjusted, just the thing for going from fairgrounds cruising altitude to a more realistic over-the-road height, while maintaining the preferred ride quality in either.

In terms of real-world performance, CLASS is indeed impressive. We had the opportunity to ride in a Ford E-450, similar to the small shuttles often seen at airports and equipped with a system on the rear wheels only. Because of the disparity between the empty and loaded weights and the spring rate necessary to deal with the maximum load, these things would normally jar your teeth loose when empty. But with the LiquidSpring system, the ride was surprisingly smooth, even over railroad tracks, and the body roll normally associated with a vehicle with such a high center of gravity was minimal.

While CLASS seems to be the ideal suspension system for street rods in most respects, there is presently one drawback: the size of some of the components. While the struts themselves aren't too much bigger thansome coilovers, the corner manifolds and supplemental fluid tanks would be difficult to package in most street rods. However, the system we saw and photographed was designed for a 3/4-ton Ford pickup and was capable of handling four times the weight of the heaviest street rods. And while a system appropriately sized for a street rod would still require the corner manifolds and tanks, it is possible that they could be downsized enough that they would at least be easier to hide. Perhaps if enough interest is shown, LiquidSpring will make repackaging some of the components a priority. After all, if LiquidSpring can adapt components from a mining truck to a pickup, they're hot rodders at heart.