Car Advice

Explained: What is a Damper and How does it work?

Everyone knows that a car’s suspension has something called a damper. In our latest five-minute explainer we explain what a damper is and how it works.

You’ve heard of dampers as part of a car’s suspension. But what are they really, and how do they work? Okay, time for a backyard experiment. You’ll need a tennis ball, a bean-bag and a concrete floor. Hold the tennis ball at shoulder height and drop it on to the concrete. What happens? Yep, the ball bounces back at you, high enough for you to easily catch it.

Now, from the same height, drop the tennis ball into a bean-bag. The difference is obvious; instead of bouncing back, the ball just plops into the bean-bag and doesn’t really rebound at all. While the unyielding concrete preserves the energy in the ball (allowing it to spring back at you) the bean-bag has absorbed all of the ball’s energy and dissipated it as a force to rearrange the beans inside the bag (as well as some noise and a microscopic amount of heat through the friction involved).

In terms of your car’s suspension, the tennis ball is the spring and the bean-bag is the damper, also – for obvious reasons – known as a shock-absorber.

Of course, you don’t have bean-bags cabled-tied under your car, so how does a damper work? Essentially, it uses a tube, inside which is a fluid (usually oil) and a series of internal baffles (holes). As the spring moves up and down, the damper telescopes, forcing that oil through the holes. That has the effect of slowing the whole process as well as controlling it and dissipating the energy so that the spring (the tennis ball, remember) doesn’t continue to bounce.

Without dampers, a car would hit a bump and set up an oscillation that would grow with each new bump until it literally bounced you off the road.

You can check the condition of your dampers with a fairly simple test at home: Push down sharply on each corner of the vehicle. It should dip and then return to its normal position in one motion. If it continues to bounce or wobble, chances are your dampers are completely baked. The other thing to do is to stick your head under the car and look at the dampers individually. If there’s any oil or oil-mist on the outer body, they’ve started to leak and need to be replaced.


Dave Morley

Dave Morley