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Replacing Shock Absorbers

Don't be a stick, or a rubber ball, in the mud

Ah, the miracle of the modern automobile. Turn the key and within seconds thousands of pounds of technology assembled from parts made all over the world is rolling down the road unabated, as if gliding on an invisible cushion of air. The tires, suspension, springs, and shock absorbers are all seamlessly engineered to provide a smooth and predictable ride. The shock absorber is at the heart of the suspension. The obvious benefit of a shock absorber is that—working together with the springs—the shocks soak up the bumps and deliver a smooth ride. Without the shocks the car would flail about wildly on the springs.

This leads into the secondary and less obvious benefit of shock absorbers—control. The four small patches of tire making contact with the pavement will not do much good if the tires are bouncing all over the place and spending more time in the air than on the ground. Brakes and steering become dangerously ineffective. For reasons of safety and comfort, inspecting your shock absorbers once a year or every 12,000 miles is a good idea. Worn shocks are not only uncomfortable, but can also be dangerous.

Damp and Damper

A good way to think about a shock absorber is by indulging in a muddy analogy. Imagine taking a rubber ball and bouncing it down onto a hard surface, like a concrete road. The ball bounces up against the concrete. Boing. The energy in that ball is similar to the energy in the springs that support the suspension of the modern automobile. As a car or truck hits a bump, the weight of the car pushes down onto the spring. With the weight of the car or truck stored in its coils, the spring wants to push back up. The car bounces. The spring is like the rubber ball. Take that same rubber ball and throw it into some thick deep mud instead of hard concrete, and it will not bounce. It will stop dead. This is how the shock absorber works. Inside the shock absorber is a cylinder full of oil, and sometimes a pressurized inert gas—the mud, so to speak.

Through a series of valves, the shock absorber uses this oil and gas to dampen the energy of the spring, and keep the car from bouncing. The tires stay on the road where they belong. Control is maintained. The vehicle rides smoothly. Unfortunately the valves and seals inside the shock absorbers get beaten up with all the jouncing, and eventually wear out. Bumpy roads or over-enthusiastic driving can accelerate this process.

Strut Your Stuff

Bouncing about the road while attempting to drive is the most glaring sign of worn shock absorbers. Cupped wear on tires is another sign that the shocks have seen their last days. Worn shock absorbers wear out tires in cupped strips or patterns because the tires spend half their time in the air, and the other half on the pavement. Four bouncing balls with a car on top of them is not the best scenario for superior handling or long tire life.

Removing and replacing the shock absorbers is usually a relatively straightforward nuts-and-bolts type procedure. In a simple shock and spring suspension arrangement, replacement involves raising the vehicle and replacing the shock and grommets. If the shock absorber and spring are joined together as a MacPherson-style strut assembly, a tool called a spring compressor is required to liberate the shock absorber or strut insert. The best way to find out if the shock absorbers are of the divorced spring and shock, or MacPherson variety, is to take a look either under the vehicle or in a service manual.

Always check all suspension components when replacing shock absorbers. Chances are if the shocks are shot, parts attached to them have also taken a hit. Arm yourself with knowledge before beginning to prevent any shocking moments.