Loading…
The theoretical point about which the sprung mass (body) of the car rolls relative to the unsprung mass (wheels and axles). Roll center height affects both body roll and how lateral forces transfer through the suspension.
Staniforth's Car Suspension explains: "The roll centre is a notional point which can be drawn. It is a result of the instant centre of rotation, and is constructed by looking at the angles between the ball-joint pivot point and the inner control-arm mounting and the upper mounting plane. At the point where these intersect, a line is drawn back to the centre of the tyre contact patch." Carroll Smith's Racing Chassis and Suspension Design provides the force-based definition: "the roll centers are defined as points at which lateral forces are transferred between the sprung and unsprung masses and are not used to define the kinematics of the sprung mass." The SAE definition adds that it is "the point in the transverse vertical plane through any pair of wheel centers at which lateral forces may be applied to the sprung mass without producing suspension roll." A higher roll center reduces body roll but increases jacking force — a key trade-off in suspension geometry.