Editing Suspension: designs, shapes, sizes (section)
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===Solid axle=== [[Image:Shock absorber.JPG|thumb|400px|right|Solid rear axle with leaf springs]] ====Leaf spring==== Leaf spring rear suspension is much like a front leaf spring suspension minus the steering linkage and knuckles. Two leaf springs are mounted longitudinally in the chassis and attach at their ends to the frame both at the front and back. Normally, one end of the spring is solid-mounted with a bolt/nut through a bushed eye to a bracket on the frame and the other end is connected through a shackle arrangement which allows no binding as the length of the spring changes during upward and downward movement of the differential. A solid axle differential is then mounted somewhere near the center of the springs. The springs also act as a lateral locator, though a Panhard bar can be added to alter the roll center and to more positively locate the axle. <br style="clear:both"/> ====Triangulated 4 Link==== [[File:Triangulated 4-link.jpg|thumb|300px|left|Triangulated 4 link rear suspension]] Two longitudinally straight lower control arms and two angled upper control arms hold the rear end in place horizontally while allowing it to move vertically. This setup allows for the use of coilovers or coil springs and shocks. This "triangulation" of the upper control arms keeps the rear axle centered, thus no Panhard bar is necessary with this set-up. <br style="clear:both"/> ====Parallel 4 Link==== Two straight lower control arms and two straight upper control arms provide superior axle roll control during a hard launch. This set-up is commonly found in drag racing applications. This suspension design has no provision to keep the rear axle centered so a centering device like a Panhard bar or Watt's link must be used. ====3 Link==== 3-Link suspension is a design of rear suspension which has 3 trailing (longitudinal) arms on a solid rear axle connecting it to the frame. The two bottom lower links typically mount toward the outboard end of the axle on the underside and are parallel in top view. The third link can be centered on top of the third member on center, or is commonly mounted toward the right side of the car to help counteract engine torque. This type of linkage arrangement is excellent for handling as it allows for much freedom of movement in rotation. This system must utilize a lateral locator such as either a Panhard bar or Watt's link for centering the rear axle. Coil springs and shocks are used in this setup or a coil-over setup can be used. [[File:9614-tri-5 custom 48inch ladder bars-lg.jpg|thumb|350px|right|Custom 48 inch ladder bar rear suspension]] ====Ladder bar==== V-shaped bars which attach the front point of the bars to the frame toward the front of the car and the other end to brackets which are welded to a solid axle differential housing. At the housing brackets, the differential may be "clocked" or rotated to change the pinion angle. At the front, or Vee point of the bars, they may be moved up or down in their brackets to change the way the load of the differential is fed into the frame structure of the car. Ladder bars are a low-cost way of controlling differential rotation, although they may be overly harsh in a street application. Where the car has to negotiate an uneven entry or exit such as angling into or from a driveway, there is no compliance in the bars like there would be in an OEM system. You could find one of the front tires being pulled off the surface of the roadway due to chassis twist and non-conformity of the bars. Another peril is the bending or breaking of brackets or welds from the flexing, a good reason to limit ladder bars to a race-only vehicle. At least one manufacturer has addressed this non-conformity. Auto Weld Chassis has developed a compliant urethane member in the Vee-point. This is a low-cost, new generation of ladder bars for Pro-Street use. They place a heavy duty urethane bushing in the front with a heavy duty outer sleeve welded directly to the ladder bars for extra strength. The bushing has an inner steel sleeve which accepts a drag legal 3/4" bolt. Stainless steel adjusters and double shear plates are employed at the back of the bars. The flexibility of the urethane bushing allows the rear to twist and float slightly to soak up road irregularities and bumps for a better handling, quieter, maintenance-free ride that is still able to supply the necessary traction. Ladder bars may be used to control axle rotation with a leaf-spring arrangement or may be used with coil-overs or coils/shocks using a Panhard bar or Watts Link to control lateral body movement in relation to the differential housing. ====Truck arm==== A truck arm suspension uses two I-beam section links that mount wide at the axle and close together at the center of the car. The arms mount solidly (with U-bolts) at the axle and on bushings at the frame. This suspension was originally used on '60s-early '70s Chevrolet/GMC light trucks. Junior Johnson was the first car builder to use a truck-arm suspension in NASCAR. It was so successful, it is now the mandated standard suspension. The GM arrangement was compromised in several respects. The Panhard bar was too short for the long suspension travel inherent in light trucks, resulting in excessive lateral body movement in relation to the axle housing. The shock absorbers were mounted at the wrong angles. This arrangement is over constrained and relies on deflection of the links and bushings in order for the body to roll. Because of this it acts like a built-in anti-roll bar. However, the rate cannot be adjusted without replacing the bushings at the front mounting point of the arms. This is something to be aware of when upgrading from factory to heavy duty aftermarket arms. A Panhard bar is traditionally used for lateral restraint, although a Watts Link could also work. ====Torque arm==== A torque arm setup utilizes two lower control arms while having a unique arm which attaches near the center of the rear end near the pinion. This third torque arm extends all the way to the transmission tailshaft or crossmember. It can use either coilovers or a coil spring and shock setup. Also this setup (like the 3-link) requires either a Panhard bar or Watts link for centering the rear axle. This system is known to be a good handling set up, however during hard launches the flexing of the torque arm can change pinion angle. One solution to this problem is to buy a sturdier aftermarket torque arm.
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