A double wishbone suspension is an independent suspension design for automobiles using two (occasionally parallel) wishbone-shaped arms to locate the wheel. Each wishbone or arm has two mounting points to the chassis and one joint at the knuckle. The shock absorber and coil spring mount to the wishbones to control vertical movement. Double wishbone designs allow the engineer to carefully control the motion of the wheel throughout suspension travel, controlling such parameters as camber angle, caster angle, toe pattern, roll center height, scrub radius, scuff and more. Implementation 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. A single wishbone or A-arm can also be used in various other suspension types, such as variations of the MacPherson strut. The upper arm is usually shorter to induce negative camber as the suspension jounces (rises), and often this arrangement is titled an "SLA" or "short long arms" suspension. When the 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. To resist fore-aft loads such as acceleration and braking, the arms require two bushings or ball joints at the body. 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. Alternatively, a fixed-length driveshaft can perform the function