Which adjustment is likely to be out of specification if the front wheels do not return to the straight ahead position after rounding a turn?

The situation described, where the front wheels do not return to the straight-ahead position after rounding a turn, is typically indicative of an issue with caster adjustment. Caster refers to the angle of the steering pivot point from the front to the rear of the vehicle when viewed from the side. A positive caster angle helps the wheels to return to the straight-ahead position after a turn, as it creates a self-centering effect due to the weight distribution over the wheel.

In vehicles with insufficient caster, the steering may feel off-center, and the wheels may not properly align back to the straight position after completing a turn, leading to handling issues and an unresponsive steering feel. Therefore, if the wheels fail to return to this position correctly, it strongly suggests that the caster angle is out of specification.

Other adjustments like camber, toe, and tracking primarily affect tire wear and vehicle alignment but do not significantly influence the self-centering action required for returning the wheels to the straight-ahead position. Thus, any defect associated with these parameters would not typically impact the wheel's ability to return post-turn as severely as a misaligned caster would.