Caster & Camber
Looking from the front of the vehicle, camber is the inward or outward tilt of the top of wheels. When the tops of the wheels are tilted in, this is negative camber; if they are tilted out, it is positive. In a turn, a slight amount of negative camber helps maximize contact of the tire with the road. However, too much negative camber compromises straight-line stability, increases rolling resistance, bump steer and tighten steer.
Although not adjustable from the factory, adjustable front camber plates are available from aftermarket suppliers. Suspension tuning is a key element in improving the cornering ability of a vehicle, and should only be performed by a knowledgeable and experienced technician.
On E36 models, the rear camber is adjusted by loosening the locknut of a through bolt, and moving an eccentric washer that is keyed to the bolt.
Looking at a vehicle from the side, caster angle describes the steering axis rather than a wheel angle. The steering knuckle is attached to a strut at the top and a control arm at the bottom. The wheel pivots around the line between these points to steer the vehicle. When the upper point is tilted back, this is described as positive caster. Having a positive caster tends to make the wheels self-centering, increasing directional stability. Excessive positive caster makes the wheels more difficult to steer, while an uneven caster will cause a pull to one side. Overloading the vehicle or sagging rear springs will affect caster, as will raising the rear of the vehicle. If the rear of the vehicle is lower than normal, the caster becomes more positive, conversely as the rear is raised, the camber is reduced.
If the front caster varies from side to side, the lower subframe fasteners can be loosened and the subframe moved slightly around the bolt holes for minute adjustments.
Although not adjustable from the factory, adjustable front caster/camber plates are available from aftermarket suppliers. Suspension tuning is a key element in improving the cornering ability of a vehicle, and should only be performed by a knowledgeable and experienced technician.
Looking down at the wheels from above the vehicle, toe angle is the distance between the front of the wheels, relative to the distance between the back of the wheels. If the wheels are closer at the front than at the rear, they are said to be toed-in or to have negative toe. A small amount of negative toe in the front end enhances directional stability and provides a smoother ride on the highway, however too much toe in will cause the front of the car to dart, or turn in quickly on a turn. A slight toe out may improve the ultimate turn-in ability of the vehicle, however too much toe out may cause the mid corner performance to be compromised and create excessive understeer.
The rear toe should typically be set for toe in. Toe out should only be approached by a professional suspension expert for extreme cases where extensive modifications have been performed and the use of specific components require ignoring factory specifications.
The front toe is adjusted on both E30 and E36 models by loosening a locknut and then rotating a threaded steering arm.
The rear toe on E30 models is adjusted by using eccentric bushings in the trailing arms. On E36 models, the toe is adjusted by loosening the three lower trailing arm bushing holder bolts, and moving the trailing arm.