Where is something fundamental revealed in this picture on the subject: hydraulic brake? It shows the unit for operating a dual-circuit brake in the racing area. Two reservoirs for the brake fluid, supplying the front and rear brakes, are easy to spot.

The brake pedal, with its absolutely fixed pivot point, ends in between and, when pressed, pushes a cross bolt backwards from our point of view. One might think that it always acts equally on the pistons of the two cylinders, but far from it.

The cross bolt is also called a balance bar and it has a thread so that the force from the pedal can be directed more to the right or left. The arrow shows where a Bowden cable ends, which makes this balance bar adjustable by turning a knob on the dashboard.

Of course, the pedal does not move in the middle when turning, but the two piston rods move. The one closest to the pedal then gets more power when you step on the brake pedal and the other less power, the whole thing can be regulated during the race.

What do we learn from this? Front/rear braking force distribution is so important that it not, as is the case with production vehicles often predetermined fixed, but can even be changed during the race, e.g. when the tank is slowly getting empty. One really wants to avoid the car braking harder at the rear than at the front, because that creates instability.

One could assume, as later practiced when designing ABS, that stable braking is even more important than particularly effective braking. Normally, except perhaps with a very heavily rear-loaded car, the necessary braking force is greater at the front than at the rear. It is also based on the driving performance and the permissible total weight.

Faster vehicles don't necessarily need as much larger brake discs as the inner space of the rims grows, which sometimes makes them look a little lost. Driving down the mountain pass with a kind of continuous braking at low speed in order to cool the brakes is still a special requirement.

Which brings us to the second major challenge, heat dissipation. It is said that a gray cast iron brake disc can withstand temperatures of up to 700°C. If you see them glowing red through the rim, then it is already at least 800°C. Needless to say, legal requirements are far exceeded these days.

What makes the design of the brakes difficult is, for example, a short wheelbase, which is easy to understand with the old Smart, and a high center of gravity. And to put it in figures: before ABS came along, the rear axle was not allowed to block at decelerations of up to 0.8 g. But even then there were so-called hydraulic anti-lock braking system.

Since you want all wheels to be braked equally, the large selection of tires with mostly the same brake system can pose a problem when buying a new one. Not only the width of the contact area plays a role here, but also the different stiffness of the flanks depending on the ratio of height to width.

The formula compares the force used to apply the brake with the resulting circumferential force. Dividing the two results in what is known as a brake parameter, which is greater the more the brake converts the force acting on its linings into circumferential force, with disc brakes being less than with drum brakes.

In the case of drum brakes, this is called self-self-enforcement. The corresponding chapter explains why this is not so popular with the service brake, especially at the front, at most with the parking brake, but then at the rear. Because of the disc brake, however, almost all cars nowadays need brake boosters. And woe, it fails and the drive is continued.

It's unbelievable how sensitive people are to pedal characteristics. One needs the feedback. Attempts e.g. at Citroën to completely negate this by using a button as a brake pedal were very soon abandoned. The introduction of recuperation during braking was also made much more difficult by the fine-tuning of the boundary between this and the onset of the braking effect.