The paper presents the results of investigations of a railway disc brake system related to the mass wear of its brake pads. The tests were carried out on a certified brake stand designed to determine the friction-mechanical characteristics of the brakes. The test stand was additionally equipped with a thermographic camera to observe the contact points of the brake pads with the disc. Particular attention was drawn to investigating the impact on the mass wear of the brake pads of such parameters of the braking process as contact surface of the brake pad with the rotor, thickness of the brake pads as the indicator of their initial wear, clamping force of the pads against the rotor, rail vehicle mass to be decelerated, and speed, at which the deceleration begins. The scientific aim of the paper is to present the relations between the mass wear of the brake pads and the quantities that characterize the braking process. A regression model was determined to estimate the wear of the brake pads based on a single braking process with the preset input quantities.