Steering & Suspension

   Before there was MacPherson struts, there was the basic hydraulic shock absorber. Again, something that hasn't changed too much since it's use started sometime in the 1930's.

   The operating principle of standard hydraulic shock absorbers is in forcing fluid through restricting openings in the valves. This restricted flow serves to slow down and control rapid movement in the car springs as they react to road irregularities. Usually, spring-loaded valves control fluid flow through the pistons. Hydraulic shock absorber automatically adapt to the severity of the shock. If the axle moves slowly, resistance to the flow of fluid will be light. If the axle movement is rapid or violent, the resistance is stronger, since more time is required to force fluid through the openings.

   By these actions and reactions, the shock absorbers permit a soft ride over small bumps and provide firm control over spring action for cushioning large bumps. The double-acting units must be effective in both directions because spring rebound can be almost as violent as the original action that compressed the shock absorber.

   Some vehicles came with a control that allowed the driver to select the ride type. By setting a control in the passenger compartment, a motor on the top of the shock would rotate a set of different sized valves inside the shock to change the damping ability of the shock. There are usually three settings, Firm, Normal and Soft.

   In an active suspension system there is a small sonar unit mounted in the bottom of the front bumper. The sonar unit sends a signal down onto the road and takes a "picture" of the road surface. This "picture" is sent to a control unit to automatically change the valving inside the shock to compensate for the road surface and maintain a smooth ride.

   Another important part of the suspension is the spring. The three types of springs used are the coil spring, leaf spring and torsion bar.

   Coil springs and torsion bars are generally used in the front whereas leaf springs are generally used in the rear. Coil springs are generally installed between the upper and lower control arms with the shock absorber mounted inside the spring. In some cases the coil spring is mounted on top of the upper control arm and a spring tower formed in the front-end sheet metal. Coil springs come in many "rates" and can be used to change the handling and ride characteristics of a vehicle.

   Leaf springs are made from layers of spring steel bolted together through the center of the leafs. This center bolt locates the spring to the axle housing and is attached to the housing with large U bolts. The ends of the leaf spring are attached to the frame or body through a shackle that allows the spring to flex without tearing out. The leaf spring also acts as control arms to keep the axle housing in proper position.

   Most trucks with a solid beam front end still use leaf springs on the front. Some cars, most notably the Chevrolet Corvette, use a single leaf spring, front and rear, transversely mounted. In other words the springs are mounted 90° to the center of the car.

   Okay, now I know that someone out there is saying that a torsion bar is not a spring. But in the technical sense it is. The torsion bar provides its spring action by the twisting of a flexible steel bar. This twisting of a steel bar provides the resistance to the up and down movement of the front end. There are two torsion bars, one for each front wheel. The rear of the torsion bar is mounted on the frame of the vehicle and the front is bolted the lower control arms. The big advantage of a torsion bar is that it is easily adjustable. By turning the tensioning bolts you can adjust the ride height very easily.

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