【正文】 spension proper. The ChassisThe suspension of a car is actually part of the chassis, which prises all of the important systems located beneath the car39。 The frame structural, loadcarrying ponent that supports the car39。 The suspension system setup that supports weight, absorbs and dampens shock and helps maintain tire contact The tires and wheels ponents that make vehicle motion possible by way of grip and/or friction with the road So the suspension is just one of the major systems in any vehicle. With this bigpicture overview in mind, it39。s springing systems are based on one of four basic designs: Coil springs This is the most mon type of spring and is, in essence, a heavyduty torsion bar coiled around an axis. Coil springs press and expand to absorb the motion of the wheels. Torsion bars Torsion bars use the twisting properties of a steel bar to provide coilspringlike performance. This is how they work: One end of a bar is anchored to the vehicle frame. The other end is attached to a wishbone, which acts like a lever that moves perpendicular to the torsion bar. When the wheel hits a bump, vertical motion is transferred to the wishbone and then, through the levering action, to the torsion bar. The torsion bar then twists along its axis to provide the spring force. European carmakers used this system extensively, as did Packard and Chrysler in the United States, through the 1950s and 1960s. Photo courtesy HowStuffWorks ShopperTorsion bars body, use the pressive qualities of air to absorb wheel vibrations. The concept is actually more than a century old and could be found on horsedrawn buggies. Air springs from this era were made from airfilled, leather diaphragms, much like a bellows。 however, such a car is prone to dive and squat during braking and acceleration and tends to experience body sway or roll during cornering. Tightly sprung cars, such as sports cars (think Mazda Miata), are less forgiving on bumpy roads, but they minimize body motion well, which means they can be driven aggressively, even around corners. So, while springs by themselves seem like simple devices, designing and implementing them on a car to balance passenger fort with handling is a plex task. And to make matters more plex, springs alone can39。s best to look inside a shock absorber to see its structure and function. A shock absorber is basically an oil pump placed between the frame of the car and the wheels. The upper mount of the shock connects to the frame (., the sprung weight), while the lower mount connects to the axle, near the wheel (., the unsprung weight). In a twintube design, one of the most mon types of shock absorbers, the upper mount is connected to a piston rod, which in turn is connected to a piston, which in turn sits in a tube filled with hydraulic fluid. The inner tube is known as the pressure tube, and the outer tube is known as the reserve tube. The reserve tube stores excess hydraulic fluid. When the car wheel encounters a bump in the road and causes the spring to coil and uncoil, the energy of the spring is transferred to the shock absorber through the upper mount, down through the piston rod and into the piston. Orifices perforate the piston and allow fluid to leak through as the piston moves up and down in the pressure tube. Because the orifices are relatively tiny, only a small amount of fluid, under great pressure, passes through. This slows down the piston, which in turn slows down the spring. Shock absorbers work in two cycles the pression cycle and the extension cycle. The pression cycle occurs as the piston moves downward, pressing the hydraulic fluid in the chamber below the piston. The extension cycle occurs as the piston moves toward the top of the pressure tube, pressing the fluid in the chamber above the piston. A typical car or light truck will have more resistance during its extension cycle than its pression cycle. With that in mind, the pression cycle controls the motion of the vehicle39。t support vehicle weight they only control the speed at which weight is transferred in a car, not the weight itself. Because shocks and struts have so much to do with the handling of a car, they can be considered critical safety features. Worn shocks and struts can allow excessive vehicleweight transfer from side to side and front to back. This reduces the tire39。re not, kits make it easy to install the bars at any time. Suspension Types: FrontSo far, our discussions have focused on how springs and dampers function on any given wheel. But the four wheels of a car work together in two independent systems the two wheels connected by the front axle and the two wheels connected by the rear axle. That means that a car can and usually does have a different type of suspension on the front and back. Much is determined by whether a rigid axle binds the wheels or if the wheels are permitted to move independently. The former arrangement is known as a dependent system, while the latter arrangement is known as an independent system. In the following sections, we39。t been used in mainstream cars for years. Front Suspension Independent SystemsIn this setup, the front wheels are allowed to move independently. The MacPherson strut, developed by Earle S. MacPherson of General Motors in 1947, is the most widely used front suspension system, especially in cars of European origin. The MacPherson strut bines a shock absorber and a coil spring into a single unit. This provides a more pact and lighter suspension system that can be used for frontwheel drive vehicles. The doublewishbone suspension, also known as an Aarm suspension, is another mon type of front independent suspension. Doublewishbone suspension on Honda Accord 2005 CoupeWhile there are several different possible configurations, this design typically uses two wishboneshaped arms to locate the wheel. Each wishbone, which has two mounting positions to the frame and o