A safe vehicle must be able to stop and maneuver over a wide range of road conditions. To be able
to stop and maneuver quickly there must always be good contact between the tires and the road.
The suspension is responsible for keeping the tire firmly planted on the road. The suspension also
providesa comfort buffer between the rough road and the passenger cabin.
There are many different types of suspensions. Each is a compromise between comfort, cost, and road holding. To meet these compromises for each vehicle, many types of suspensions have been developed. Each design shares two essential components-springs and shock absorbers.
Some vehicles have struts instead of shocks. In reality, a strut is just a shock absorber built into a suspension link. The strut is generally replaceable as one unit. In this discussion, any reference to shock absorbers will also apply to struts.
There are also some variations in the type of springs used on vehicles. There are coil springs, leaf springs, air springs, and torsion bars. Despite the differences in design, these variations all react with the suspension in the same manner. Any further reference made to springs will be general and includes any of these types.
The Shock Absorber
The shock controls spring motion by damping (absorbing) energy from the spring.
A shock absorbs energy by forcing oil through valves whenever it is moved. It takes
a lot of energy to push oil through the valves so when the spring is done pumping, it
doesn't have much energy left to keep bouncing. Imagine running 50 yards on bare
ground – you could do it and have plenty of energy to run back again. Now imagine
running the same 50 yards through 6 inches of mud. How much energy would you
have for a return pass?
Shocks also control the reaction of the body to road undulations. A stiffer shock tends to transmit more road irregularities to the driver but will also not pitch and roll as much as a vehicle with softer shocks. Thus shocks, like springs, can be changed to obtain a personalized ride.
Shock absorber condition is difficult to evaluate. Shocks are wear items, like air filters or tires, and do need to be replaced occasionally. The Car Care Council recommends inspection at 25,000 miles and every 6,000 miles thereafter. There are some exterior signs of a damaged shock that indicate a need for replacement, but frequently a shock absorber will have stopped working without any visible indicators.
What if the shock absorber is just worn out? It is not possible, simply by examining the shock, to tell if it is functioning. One visual indication of tired shocks is worn out and cupped tires – a very expensive diagnostic technique. The only way, up until recently, to check shock performance was a test drive or bumper jounce test – both of which are very subjective. In any case it was difficult to identify the worn part because all the shocks are working together.
The Spring
Springs isolate the driver from road imperfections by allowing the tire to move over a bump without drastically disturbing the chassis. If the chassis remains fairly steady then the tires are better able to follow road contours.
While springs do an excellent job of smoothing over bumps, they will keep bouncing once started. In other words, the chassis continues swaying and the tires keep hopping long after the vehicle strikes a bump. Left uncontrolled, springs give an uncomfortable ride with very poor tire to road contact. To control this undesirable behavior, a shock absorber keeps the spring from overreacting to every bump or dip and prevent excess movement of the tire and chassis.
Springs are durable items and are easily inspected. If the ride height of a vehicle has decreased excessively or a coil/leaf has broken it is advisable to replace the springs in axle sets. Consumers also often change springs to alter their vehicle's ride and handling characteristics. Spring problems are generally easy to identify.
to stop and maneuver quickly there must always be good contact between the tires and the road.
The suspension is responsible for keeping the tire firmly planted on the road. The suspension also
providesa comfort buffer between the rough road and the passenger cabin.
There are many different types of suspensions. Each is a compromise between comfort, cost, and road holding. To meet these compromises for each vehicle, many types of suspensions have been developed. Each design shares two essential components-springs and shock absorbers.
Some vehicles have struts instead of shocks. In reality, a strut is just a shock absorber built into a suspension link. The strut is generally replaceable as one unit. In this discussion, any reference to shock absorbers will also apply to struts.
There are also some variations in the type of springs used on vehicles. There are coil springs, leaf springs, air springs, and torsion bars. Despite the differences in design, these variations all react with the suspension in the same manner. Any further reference made to springs will be general and includes any of these types.
The Shock Absorber
The shock controls spring motion by damping (absorbing) energy from the spring.
A shock absorbs energy by forcing oil through valves whenever it is moved. It takes
a lot of energy to push oil through the valves so when the spring is done pumping, it
doesn't have much energy left to keep bouncing. Imagine running 50 yards on bare
ground – you could do it and have plenty of energy to run back again. Now imagine
running the same 50 yards through 6 inches of mud. How much energy would you
have for a return pass?
Shocks also control the reaction of the body to road undulations. A stiffer shock tends to transmit more road irregularities to the driver but will also not pitch and roll as much as a vehicle with softer shocks. Thus shocks, like springs, can be changed to obtain a personalized ride.
Shock absorber condition is difficult to evaluate. Shocks are wear items, like air filters or tires, and do need to be replaced occasionally. The Car Care Council recommends inspection at 25,000 miles and every 6,000 miles thereafter. There are some exterior signs of a damaged shock that indicate a need for replacement, but frequently a shock absorber will have stopped working without any visible indicators.
What if the shock absorber is just worn out? It is not possible, simply by examining the shock, to tell if it is functioning. One visual indication of tired shocks is worn out and cupped tires – a very expensive diagnostic technique. The only way, up until recently, to check shock performance was a test drive or bumper jounce test – both of which are very subjective. In any case it was difficult to identify the worn part because all the shocks are working together.
The Spring
Springs isolate the driver from road imperfections by allowing the tire to move over a bump without drastically disturbing the chassis. If the chassis remains fairly steady then the tires are better able to follow road contours.
While springs do an excellent job of smoothing over bumps, they will keep bouncing once started. In other words, the chassis continues swaying and the tires keep hopping long after the vehicle strikes a bump. Left uncontrolled, springs give an uncomfortable ride with very poor tire to road contact. To control this undesirable behavior, a shock absorber keeps the spring from overreacting to every bump or dip and prevent excess movement of the tire and chassis.
Springs are durable items and are easily inspected. If the ride height of a vehicle has decreased excessively or a coil/leaf has broken it is advisable to replace the springs in axle sets. Consumers also often change springs to alter their vehicle's ride and handling characteristics. Spring problems are generally easy to identify.
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Copyright 2008 - All Rights Reserved - Site Design by Montana Grafix
Copyright 2008 - All Rights Reserved - Site Design by Montana Grafix
