The moment when a tire begins to skid during braking. A tire's maximum braking force occurs when it is on the verge of lockup. Ideally all four tires should approach lockup simultaneously to give a vehicle the best braking. Because this ideal is hard to create in the real world, one end tends to lock up before the other. Front-wheel lockup is inherently more stable than rear-wheel lockup. Anti-lock brakes provide the best type of braking because it rapidly releases pressure on the brakes to prevent lockup.