Q: What is a ball joint on a suspension arm and why would it wear out?

A ball joint is the pivoting connection that lets a control arm move with the suspension while the wheel steers and travels. It carries load constantly, so it counts as a wear item. Rough roads and repeated high-grip cornering both accelerate that wear. On the Model X FUCA Ultimate Edition, this replaceable pill/ball joint is what carries the front camber, caster, and toe adjustment, so keeping it fresh keeps your alignment honest.