Bump, Memory, and Torque Steer
Bump Steer: Bump steer occurs when a vehicle is traveling down the road in a straight line, hits a bump and suddenly pulls to one side. This 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 will also result in a change in tie rod height in a power steering rack system.
Memory Steer: A vehicles steering wheel is supposed to return to within 30º to 60º of center after completing a turn. If the wheel does not return as specified the vehicle has this condition. Typically binding parts will cause memory steer. Look for upper strut mounts and bearings to cause this in front wheel drive vehicles. A binding gear or universal joint/flexible coupling can cause a steering wheel not to return to center. Check the adjustment of the steering sector/worm gear as it may be over adjusted.
Vehicle Wander: Vehicle wander is when a vehicle veers left or right on its own while the driver attempts to hold the wheel in a straight line. This condition is typically caused by loose steering components. Leave the vehicle on the ground and have a helper turn the wheel left and right. Look for any loose components like the idler arm, pitman arm, center link, and tie rods. Loose ball studs and elongated bores are common problems with these components. It’s common for the ball socket of the inner tie rod end to become loose changing the tires toe as the vehicle travels down the road. The same is true for the ball stud of the outer tie rod end.
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. Some vehicle manufacturers have created vehicles with shafts of equal length to compensate for this phenomenon. Different tread patterns or different size tires will also result in torque steer.
