What is threshold braking and why is it difficult to do with ABS?

• A. Threshold braking is applying brakes to the limit just before wheel lock to maximize deceleration; with ABS, the system prevents lock but reduces feedback and may obscure the exact limit.
• B. Threshold braking means braking as hard as possible after wheel lock.
• C. ABS makes threshold braking easier by providing direct feel of the limit.
• D. Threshold braking is not possible with modern brakes.

Answer: (A)

Threshold braking means applying brake pressure up to the point just before the tires start to slip or lock, so you get the maximum possible deceleration while keeping rolling contact. It depends on sensing the grip and the subtle changes in how the tire and brakes feel as you approach that limit, then easing off slightly to stay right at that boundary between static and kinetic friction.

With ABS, the brakes are constantly modulated to prevent wheel lock. That automatic control removes the direct, fine feedback you rely on to know you’re at the exact limit. The system prioritizes keeping the wheels turning and maintaining steering control, which can blur the sense of the precise moment you’re at the grip boundary. So while ABS helps prevent lock and keeps you pointed straight, it makes reaching or holding the exact threshold more challenging, because the feel you’d use without ABS isn’t the same.

In contrast, the idea of braking after the wheels have locked isn’t threshold braking, and the notion that ABS provides a clearer feel of the limit isn’t accurate—the system changes how the limit is perceived. And threshold braking is still possible with modern brakes, though the feedback and the approach change once ABS is involved.