On freight wagons with a disc brake, there are two brake discs between the wheels on each axle of the wheel axles, most often 590 mm (or 610 mm) in diameter and 170 mm wide. Other sizes are also possible.
For each brake disc there is an individual lever brake system with its own brake cylinder. Each bogie is controlled separately by its own weighted valves and cargo brake valve.
This means that all four brake cylinders in one bogie are supplied with one pressure. Skid protection is generally not available on freight cars.
Indicator device
Brake indicator devices are placed on the frames on each side. With the help of these indicator devices, the function of the brake can be checked.
One field is available for each bogie, which changes to a red display (= brake is active) when the pressure in the brake cylinder exceeds 0.4 bar.
If the pressure in the brake cylinder is less, then this is represented by a green display.
If the brake is off (no more pressure in the auxiliary air tanks) then this is indicated by a white readout with a black X.
Damaged indicator devices must be replaced, also when the observation window is full of condensate water.
Brake cylinder
Brake cylinders for disc brakes have an integrated adjustment mechanism that only works in the direction of pad wear (simple acting).
When changing pads, therefore, the brake cylinder must be manually rotated back into the front end of the piston rod with the adjusting screw to make room for the new, thicker brake pads.
By applying and releasing the brake several times after changing the brake pads, the brake cylinder adjusts itself again to the factory-set clearance between the brake pad and the brake disc.
When in a repair depot, the brake cylinders should be visually inspected for damage.
Particular attention should be paid to the sealing of the rubber sleeve for the piston rod, which should not be torn or leaky.
Damaged brake cylinders must be replaced. Due to the complex technique, they should only be opened and repaired in approved specialized repair depots.
Lever brake system
For freight wagons with a disc brake, a separate lever brake system is installed for each brake disc.
A brake cylinder works with two brake levers that push the pad holder against the brake disc.
The brake cylinders are adjusted so that a clearance between the brake disc and the brake pad of max. 3 mm on each side.
The resulting wear is compensated by an automatic adjustment in the brake cylinder. When installing new brake pads, the cylinder at the front sleeve on the piston rod must be turned back again by hand.