What does "toe-in" refer to in vehicle alignment?

"Toe-in" refers to the alignment condition where the front wheels of a vehicle point inward toward each other at the front, creating an angle that is narrower at the front than at the rear. This alignment is crucial for ensuring that the vehicle tracks straight while driving. When the wheels are properly set to "toe-in," it can improve handling and stability during movement and can also help reduce tire wear caused by uneven contact with the road surface.

In contrast, the other options describe different aspects of wheel alignment or positioning. For example, the outward angle of the wheels pointing away from each other is referred to as "toe-out," which has different implications for handling and tire wear. The angle of the wheels in relation to the vertical plane refers to camber, which concerns whether the wheels tilt inwards or outwards when viewed from the front. Meanwhile, the overall alignment of the front end suspension system encompasses various aspects of alignment, including camber, caster, and toe, rather than being a specific measurement like "toe-in" itself. Understanding "toe-in" is vital for maintaining optimal vehicle performance and tire longevity.