Unsourced material may be challenged and removed. The double-wishbone suspension can also be referred to as “double A-arms”, though the arms themselves can be A-shaped, L-shaped, or even a single bar linkage. SLA” or “short long arms” suspension. When double wishbone suspension system pdf vehicle is in a turn, body roll results in positive camber gain on the lightly loaded inside wheel, while the heavily loaded outer wheel gains negative camber.
Between the outboard end of the arms is a knuckle. The knuckle contains a kingpin for horizontal radial movement in older designs, and rubber or trunion bushings for vertical hinged movement. In newer designs, a ball joint at each end allow for all movement. Attached to the knuckle at its center is a bearing hub, or in many older designs, a spindle to which the wheel bearings are mounted. At the knuckle end, single ball joints are typically used, in which case the steering loads have to be taken via a steering arm, and the wishbones look A- or L-shaped. An L-shaped arm is generally preferred on passenger vehicles because it allows a better compromise of handling and comfort to be tuned in.
The bushing in line with the wheel can be kept relatively stiff to effectively handle cornering loads while the off-line joint can be softer to allow the wheel to recess under fore-aft impact loads. For a rear suspension, a pair of joints can be used at both ends of the arm, making them more H-shaped in plan view. The various bushings or ball joints do not have to be on horizontal axes, parallel to the vehicle centre line. If they are set at an angle, then anti-dive and anti-squat geometry can be dialled in.
In many racing cars, the springs and dampers are relocated inside the bodywork. As the wheel rises, the push rod compresses the internal spring via a pivot or pivoting system. The opposite arrangement, a “pull rod”, will pull on the rod during bump travel, and the rod must be attached to the top of the upright, angled downward. It also reduces the wear of the outer edge of the tire. SLAs can be classified as short spindle, in which the upper ball joint on the spindle is inside the wheel, or long spindle, in which the spindle tucks around the tire and the upper ball joint sits above the tire.