Shock & Struts

The primary function of your car's suspension and steering systems is to allow the wheels to move independently of the car, while keeping it "suspended" and stable. Any play or uncontrolled motion in these systems results in a deterioration of handling and accelerated tire wear. Vehicle alignment is closely tied to the condition of the suspension and steering systems.

Suspension System

Worn or loose components affect the suspension system's ability to control motion and alignment angles, resulting in a deterioration of vehicle handling and stability, and accelerated tire wear. The main components of the suspension system are:

How Car Suspensions Work

An automobile engine wastes a lot of energy in the form of heat. Left unchecked, that heat can build up and start damaging not only the engine itself, but the surrounding parts. It's important, then, that temperature of your car's engine be kept below a certain level. That job falls to the coolant system, which pumps coolant -- usually water mixed with ethylene glycol (aka antifreeze) -- through the engine to absorb the heat. Once it becomes heated, the water is circulated back to the radiator, where the heat is transferred to the cooling fins and radiated into the air. This cools the water and antifreeze mixture, which can then repeat its journey through the engine.

Without a radiator to remove the heat from the coolant, your car would quickly overheat and the engine would begin to destroy itself. So having a working radiator in your car is essential to the vehicle's proper operation. But how long can you expect your radiator to continue doing its job? Most auto mechanics feel that a properly maintained radiator should last for at least eight to 10 years. Older metal radiators, when well maintained, can last for the life of the car, but modern radiators are mostly made from plastic rather than metal, and plastic expands and contracts as the radiator heats and cools.

Over time this leads to cracks, though it's rare for this to happen in less than a decade. To achieve the maximum lifetime for your radiator, it's important to have the coolant system flushed out as often as your car's manual suggests, so that the water and antifreeze mixture continues to flow properly. And, of course, make sure that the radiator always contains the proper level of coolant, since coolant can escape when the radiator overheats. If you frequently find that the level of coolant is too low it may mean that you have a leak. Take the car to a mechanic to have a look at your cooling system.

Other potential problems include rusty hose clamps, corrosion to the aluminum core and problems with the thermostat that regulates coolant flow. Thermostat problems will cause frequent overheating, which is a problem you should have checked out as quickly as possible.

Take good care of your radiator and it should be with you for quite a long time -- maybe even the entire life of your car. Without an intervening structure, all of wheel's vertical energy is transferred to the frame, which moves in the same direction. In such a situation, the wheels can lose contact with the road completely. Then, under the downward force of gravity, the wheels can slam back into the road surface. What you need is a system that will absorb the energy of the vertically accelerated wheel, allowing the frame and body to ride undisturbed while the wheels follow bumps in the road. The study of the forces at work on a moving car is called vehicle dynamics, and you need to understand some of these concepts in order to appreciate why a suspension is necessary in the first place. Most automobile engineers consider the dynamics of a moving car from two perspectives:

Ride - a car's ability to smooth out a bumpy road
Handling - a car's ability to safely accelerate, brake and corner

These two characteristics can be further described in three important principles - road isolation, road holding and cornering. The table below describes these principles and how engineers attempt to solve the challenges unique to each.

A car's suspension, with its various components, provides all of the solutions described.

Let's look at the parts of a typical suspension, working from the bigger picture of the chassis down to the individual components that make up the suspension proper.

How long do car shocks last?

We fill our lives with barriers to protect us from the harsh realities of life. From the roof over your head to the parental lock on your cable box, the eternal issue is always the same: How long can this barrier protect our soft, ordered little world from the barbarians at the gates?

Fancy metaphors aside, this question applies every time you climb behind the steering wheel. Your pampered cab may be a world full of satellite radio serenades, wood-beaded massage seat covers and lavender-scented air fresheners, but the road is hard, winding and bumpy. Let's go back to the barbarians at the gate analogy, shall we? The longevity of your walls of defense would depend a great deal on a number of factors. How often are the barbarians attacking, and how much damage do they inflict on the gates each time? How well do they hold up to the weather, and what are you doing to maintain them?

Pretty much the same holds true for the longevity of your vehicle's shock absorbers. Remember, whether you use gas-charged and conventional shocks, these devices deliver improved handling and a smoother ride by converting the kinetic energy of suspension movement during the drive into heat energy that dissipates through the hydraulic fluid in the shocks. Like the walls of an embattled city, there's only so much energy these shocks can absorb before they finally succumb.

As kinetic energy wears shocks down, it follows that more suspension movement has a negative effect on shock absorber life expectancy. If your morning commute consists of a smooth, unobstructed drive across level countryside, then your vehicle is probably enduring a minimum of suspension movement. Throw in some curves or a little stop-and-go traffic, and you have a lot more movement (and kinetic energy) slamming through those shocks. From there, gravel, hills and other road conditions only add to the stress on your vehicle's shocks, potentially subtracting from the typical 50,000-mile life expectancy. Even your style of driving and specific wheel and tire modifications can have an impact.

In addition to suspension movement, regional weather conditions and road contaminants can also take a toll on your vehicle's shock absorbers. After all, these are external mechanisms and regular drives through saltwater, sand or rough gravel roads can further wear your shocks down with abrasions or rust.

If you just drive the car to church on weekends, then this may all sound like great news -- not so much if you fill your Saturdays with muddy exertions into the wilderness. Luckily, you can take several steps to help maintain your defenses against all the road can throw at you.

The most important step in car shocks maintenance is simply to remember that your car has them to begin with. You can tell a great deal about their performance by simply feeling your car's suspension as you drive.

Motor Trend magazine also suggests taking your vehicle out to a secluded parking lot, accelerating to 10 miles per hour (16 kilometers per hour) and hitting the brakes. If the front of the vehicle keeps bobbling after you come to a stop, then your shocks are likely shot [source: Motor Trend]. When you're not on the road, you can get a closer peek by getting on your hands and knees and looking at these ride-softening little gadgets. If you see dents in the shock tubes, leaking oil (though a slight oil film over the lower portion of the shocks is OK), then chances are you're in the market for some new shocks.

You should also keep an eye out for loose mounting bolts and worn mounting blushing, which may also result in a rattling noise while you're driving. Your shock absorbers need a firm mounting to work properly, so you might have to replace loose bolts and blushings. In some cases, this requires the replacement of the shock absorbers themselves as some designs include the blushing as part of the shocks.

Your shocks are just one part of the vehicle's overall suspension system, so you'll want to keep an eye on such components as ball joints and springs as well.

Worn shocks don't just hamper driver comfort; they can harm overall suspension performance and reduce brake efficiency, cornering ability and antilock brake system effectiveness. So when shocks go bad, it's out with the old and in with the new.

(Source: http://auto.howstuffworks.com)