The red pointer of the watch shows just under 14 kN. This is the maximum force exerted on the pads by the single piston of this caliper brake. It is much higher with the disk brake than with the drum brake, because less lining surface generates friction.

Now you might ask why the engineers don't make this area bigger or, as in the design study by ATE for BMW above, let two calipers act on one disk? No, it's not the size of the friction surface that matters, but the heat transfer. Nothing is gained if the brake heats up too much and fading reduces the braking power.

You want to come to a standstill as quickly as possible, i.e. to convert the existing kinetic energy into heat and release it to the environment, just like the engine, which absorbs energy through fuel or electrical charge and should convert this into kinetic energy as quickly as possible. So there is braking power, by the way, always higher than the engine power, even in super sports or racing cars.

Of course, brakes almost always have something to do with the dynamics of the vehicle. It is relatively easy to set one when stationary and, for example, with the help of suitable chocks, it is no problem even with the 40- tonner. However, if the vehicle is in motion, it sometimes reacts sensitively to interference with the wheels. In the meantime, we can largely rule out axle differences, at least as far as the technology of the brake itself is concerned.

But the balance between the front and rear axles remains a problem, especially because it changes with speed. That's why a rule that we have already learned in the description of the ABS system applies here: It is better to forego some braking power than to endanger the stability of the vehicle when braking.

The brake force distribution is sometimes particularly delicate on two-wheelers, where the rear wheel can be completely relieved. A fine example are vehicles with a rear engine, which often achieve a dynamic brake force distribution of almost 50:50 due to the high load on the rear axle.