Bump Steer
Bump steer is a change in wheel steer or toe caused by suspension travel without a steering input from the driver.
How it is created
As the wheel moves through bump and rebound, the steering link and suspension arms follow different arcs. Their relative geometry can rotate the wheel carrier. Bushings, joints, subframes, and the body can add compliance steer under road, brake, or drive forces, which is related but not the same purely kinematic effect.
Bump steer can be measured for one wheel or as an axle response through heave and roll. The sign, reference position, travel direction, steering condition, and whether compliance loads are applied must accompany the curve.
Designers may tune a small response to support stability and turn-in, but unintended or asymmetric change can make the vehicle react to bumps, braking, load, or ride-height changes. Alignment at normal height alone does not reveal the full curve.
For wheel-path, steering-link, and compliance behavior, see Suspension Kinematics and Vehicle Dynamics.