Shock absorbers are part of a vehicle's suspension system. Although shock absorbers do not carry any weight, they dampen the action of the up-and-down action of the springs, wheels, and axle assemblies and prevent bouncing. Shock absorbers also make the vehicle more stable by keeping the wheels in contact with the ground while negotiating bumps. Shock absorbers are tubular in shape and attach to the vehicle's frame or body, while the other end attaches to the spring or suspension control arm. Worn shocks can cause abnormal tire wear and a bouncy ride.
Test drive your vehicle on a familiar road or street. Note if the ride is rougher than usual, if there is vague steering action, if the vehicle leans excessively on turns or has noises coming from underneath the vehicle. Know that any or all of these symptoms could mean the shock absorbers are worn and need to be replaced.
Push down firmly on the top of the bumper or the bumper on one corner of the vehicle. Release and note that if the car bounces more than once, you could have worn shocks.
Drive the vehicle onto a set of car ramps and set the parking brake. Chock the rear wheels to prevent unwanted movement. Crawl under the vehicle and locate the shock absorbers at each corner of the vehicle. Note if there are any wet spots on the shocks, indicating oil has leaked from the unit. Replace leaking shocks, as they are not dampening the ride.
Check the shock absorber mounting points. A shock absorber that is not attached on one end is not doing its job and may make a clunking or banging noise while going over bumps. Replace shocks that have broken mounts.
Check the tread on all of the vehicle's tires. Know that abnormal tire wear, such as cupping and patchy wear may indicate worn shock absorbers. Know that tire wear that is consistent around the circumference of the tire is probably not caused by worn shocks, but may be an alignment problem.
Take your vehicle to a garage and have the shock absorbers bench tested by a technician. The shock absorbers will have to be removed for this service.
Always replace shocks absorbers in pairs, such as both front shocks or both rear shocks. Ideally all four shocks should be replaced at once, as even a shock that is still working has a reduced dampening capability when compared to a new shock. Replacing only one shock or both shocks on one side of the vehicle can create ill-handling suspension or steering and can possibly cause an accident.