A stretch of road that is perfectly smooth and free of bumps is practically unheard of, yet most of the time drivers and their passengers are completely unaware of just how bumpy the roads really can be. This is because of the car's suspension system, which uses struts and springs to provide a smooth, jostle-free ride. They allow the tires to roll over potholes and bumps without shaking up the passengers like a set of maracas on Cinco de Mayo.

The suspension absorbs the tire's movement on the road so it is not transferred to the passenger compartment of a vehicle, and it also maximizes friction to improve a vehicle's stability on the road, especially during acceleration, braking and cornering. When you take a turn, the suspension redistributes the car's weight so it does not roll over. A suspension system, which is part of a car's chassis, consists of shock absorbers, struts and springs, among other parts.

When the suspension system begins to wear out, it can not only begin to be less effective at providing a smooth ride, but also cause added wear and tear to tires and affect the steering stability. Other signs of failing suspension systems include bottoming out and excessive bouncing and back-and-forth motion. You may also notice that when you apply the brakes, your vehicle's front end will dip forward or drift if the suspension is not in top condition.

Driving the car while watching for these symptoms is the first step to determining whether the suspension is in need of repair. When you notice a problem, you should make a mental note, or have a passenger write down what happened and the type of surface on which you were driving. You should also keep track of the frequency of suspension issues.

When you get back from the diagnostic drive, there are a few other tests you can administer to the suspension system. First, you can manually check how well the front suspension is working by applying a bit of force to the bumper to make the car bounce up and down. While you are bouncing your vehicle, you should feel some resistance, and once you stop and step away from the car, it should come to rest after just one up-and-down motion. If it continues to bob for a while, and if you noticed that it did the same thing when you drove it over bumps during the test drive, you may need to replace the struts.

The next step in diagnosing the health of your vehicle's suspension is to pop the hood and inspect the area where the struts attach to the frame or fenderwall. The shock towers are mounted to the car with bolts and there should be a rubber piece between the bolt and the metal. Check this for cracks or tears. You should also repeat the manual bounce test, this time watching the towers to see if they are visibly loose when the car is moving up and down. If you notice that the towers are loose, the struts may not be the culprit. Instead, the strut cap, which is located at the top of the strut and houses the bearing, may need to be replaced. This problem is also often accompanied by a knocking, bumping noise when you drive over bumps.