Choosing the Correct Suspension Bushings for Your Muscle Car!

Suspension and exhaust systems begin with all of the hard parts: hangers, pipes, control arms, struts, shocks, sway bars, and springs. Bushings and insulators are the flexible connections between the hard parts. They serve as shock absorbers and vibration isolators, providing a pivot point on which the hard parts articulate.

Energy Suspension tells us suspension bushings and the like are generally made of steel and rubber. Polyurethane is a form of rubber though we don’t think of it as rubber. Like rubber, this elastomer offers the same kind of flex that enables it to isolate noise, vibration, and harshness (NVR). Polyurethane is a synthetic rubber, as is the soft, black flexible stuff in your Chevy’s factory suspension parts, subframe, and engine mounts.

Black rubber is made from petroleum byproducts as opposed to natural rubber gum that comes from trees. Polyurethane is a reaction polymer created in a thermoset process. What’s more, polyurethane is virtually indestructible and outlasts rubber. Rubber is used to describe factory bushing material and polyurethane is used to describe Hyper-Flex—the proprietary material used by Energy Suspension.

Why is it important to have less flex from our suspension systems? Because flex slows a chassis’ response to input, creating a disconnect among the driver, the chassis, and the road. In tire and suspension testing, professionals do a step and steer test, which involves driving at a constant rate of speed, quickly dialing in a specific steering angle, holding that input, and then measuring the car’s response to that input. Most vehicles will have an initial reaction and then a secondary reaction after everything settles. While some of this “settling” is tire reaction, a great deal of it is suspension deflection, or movement.

The goal is to have a very deliberate initial response and a very minimal secondary response. Soft suspension bushings not only take longer to settle but will deflect more, causing unwanted geometry changes and sloppy handling. The same can be said with subframe and engine/transmission mounts. The engine torques one way under acceleration (positive torque) and the other under deceleration (negative torque).

Energy Suspension tells Chevy High Performance that polyurethane bushing design and manufacturing isn’t as simple as the consumer may think. We check the hardness of polyurethane and other like materials such as rubber using the durometer scale. There are two main scales followed by either A, D, or OO. An average car tire will have a durometer number of 60A while a much harder handtruck wheel is a 50D. These two systems use the same testing procedure of probe pressure into the polyurethane or rubber with an exact force and measuring deflection, however, with different probes and forces.

Energy Suspension focuses primarily on the durometer scale to gauge hardness. Think of a bushing like a mini suspension system for a particular part. There is not only the spring rate, but there is also hysteresis, or the damping of the material. How does it compress, deflect, and spring back? If you have a high spring rate and no damping, you get a car that bounces around and never settles. If you have an overdamped vehicle, you get poor impact absorption.

Bushings work the same way, where the energy is dissipated through heat in the material. One of the few downsides of polyurethane is its coefficient of thermal conductivity, which is not as beneficial as rubber. Energy Suspension gets around this by either making the material stiffer to decrease the amount of movement or by using more material to distribute the energy over a greater area.

Polyurethane bushings last far longer than rubber because they’re resistant to heat, ozone, and harsh chemicals. If you keep polyurethane parts lubricated, and you will rarely have to do this, they will last the life of your vehicle.

What kind of performance improvement can you expect from polyurethane parts? Drag racers can expect to see better 60-foot times. Road racers will see added confidence by improving lap times. Decreased component deflection will deliver better handling as well as decreased tire wear from unwanted geometry changes. CHP

Energy Suspension offers three suspension bushing color choices: blue, red, and black, depending upon the part chosen. Their complete suspension bushing kits enable you to upgrade your suspension all in one stop. Leaf spring insulators may call for longer U-bolts to accommodate the thickness on some Chevrolet models.

Here’s the same suspension bushing kit in black. Consumers often ask if there’s a difference between the red and black polyurethane bushings. There isn’t. Color has no effect on hardness.