If you’re driving and hit a bump and your car suddenly jerks to one side then something is wrong. The condition is called "bump steer," and it means your steering linkage is not mounted parallel in the chassis possibly as a result of collision or frame damage, a bent steering arm, misalignment in the chassis, or an improperly mounted steering rack.

Bump steer is not a very common condition, but it can be a very unnerving thing to experience if you’re unfortunate enough to encounter it. It is usually most noticeable when crossing a major dip or bump at speed. As the suspension bounces over the bump, it suddenly feels as if someone tugged on the steering wheel. The car twitches or jerks to one side as if it has a mind of its own. This occurs because of unequal toe changes that occur as the suspension extends and compresses. In a properly aligned car, the toe alignment of both front wheels changes equally as the suspension moves up and down. But if something causes more of a toe change in one wheel than the other, it will jerk the steering towards the side with the greatest toe change. The thing that needs to be checked is the parallelism of the steering rack and linkage with respect to the ground. The height of the outer ends of the tie rods with respect to the ground should also be measured. This will require special straightening equipment or replacement to correct.  Have a professional check it and fix it accordingly.

Source:yahooautos.com