When is a pulsation felt during braking?

A pulsation felt during braking is primarily attributed to thickness variation around the rotor braking surface. When a rotor is not uniformly thick, it can cause the brake pads to engage unevenly as they squeeze the rotor. This uneven contact leads to a pulsating feeling because the brake system is being subjected to variable pressure during each revolution of the rotor. The driver will experience this as a vibration felt through the brake pedal, especially during hard braking.

In contrast, while worn brake pads can lead to decreased braking efficiency and noise, they do not typically cause a pulsation sensation. A failing master cylinder could lead to issues such as loss of brake pressure or fluid leaks, which again would not usually result in a pulsating feeling. Similarly, low brake fluid levels could lead to air in the brake lines or compromised braking performance, but this situation would more likely create a soft feeling in the brake pedal rather than a pulsation. Thus, the specific condition of rotor thickness variation directly correlates with the sensation of pulsation during braking.