What is bump steer?

Bump steer refers to a condition wherein the car wheels move a different direction when it moves upward after hitting a bump on the road. This movement or self-steering on the car wheels are not directed by the action on the steering wheel but rather proceeds independently. Bump steer is like an involuntary movement of the car wheels secondary to its contact with a bump or hump on the road for example.

In typical car design, some bump steer is expected to occur as the wheels or tires move forward and upward upon contact with a bump on the ground or road. This tendency is measured in terms of how many degrees the front wheels steer away from the center. Ten degrees of bump steer on the front wheels is considered normal. With the tire position commonly pointing out, bump steer may also be referred to as “toeing out” of the tires. As the term suggests, the tires or “toes” are positioned outwards when there is bump steer present. The bumpier the road condition is, the more bump steer will occur in the tires which could make driving or controlling the car more difficult. Rough roads and terrains are common areas wherein bump steer commonly occurs. As many experts would warn, possible over-steering or under-steering may occur because of the tires’ tendency to steer or move by itself when the roads are bumpy and rough.

To minimize bump steer, certain configurations at the wheels and related structures must be done. As car mechanics and experts would say, bump steer may not be fully avoidable but can be prevented with the right design and layout on the part of the tires and wheels. The car’s tie rod must have the right length relative to the axle and the tires. Some adjustments may have to be made in order to prevent the tires from toeing in or toeing out too much as they handle rough roads. With too much bump steer, tires could wear off easily and the rest of the tie rod and axles will also get damaged easily.