If the wear pattern on the friction ring surface shows hot spots, this can be traced back to a 'tumbling motion' when driving. The brake pad thereby constantly comes into contact with the same point on the disc.
Measures on the brake pads (tapering, chamfer, insulating plates with half-moon cut-out) ensure that the brake pad is not pressed evenly to the brake disc when braking. This prevents the pad being pulled by the brake disc, as well as stopping noise and uneven wear. The disc brake pads affected can be distinguished by a marking on the rear of the pad.
To correctly bed-in brakes after work on the brakes, i.e. after replacing brake discs and brake pads, these must be run in.
Various brake pads were used during the construction period of the T4. The main modifications consisted in the smaller rear plates and friction surfaces