Bump, Memory and Torque Steer

Driver steering vehicle.

Bump Steer: Bump steer occurs when a vehicle is traveling down the road in a straight line, hits a bump, and now pulls to one side. It happens because one of the front tie rods is now higher than the other. This is usually caused by a worn or loose idler or pitman arm in a parallelogram steering system. Worn or damaged rack mounting bushings or loose mounting bolts cause changes in tie rod height in a power steering rack system.

Memory Steer: A vehicle's steering wheel is supposed to return to within 30┬║ to 60┬║ of the center after completing a turn. If the wheel does not return as specified, the vehicle is suffering from memory steer. Typically binding parts cause this condition. Inspect upper strut mounts and bearings on front-wheel drive vehicles. A binding gear or universal joint/flexible coupling will result in poor steering wheel return to center. Check the adjustment of the steering sector/worm gear.

Torque Steer: Torque steer occurs in FWD vehicles when the vehicle pulls to one side during hard acceleration. This is due to uneven axle shaft lengths. They pull to the side with the shortest axle. Some vehicle manufacturers have created vehicles with shafts of equal length to compensate for this phenomenon. Different tread patterns or different size tires also result in torque steer.

Vehicle Wander: Vehicle wander occurs when a vehicle veers left or right on its own while the driver attempts to keep the vehicle in a straight line.