Since wheel loads, road surface and thus the friction value of the wheel-road interface are constantly changing, it is a high technical achievement to design a braking system in such a way that it provides maximum braking power without exceeding the maximum force (i.E. The wheels lock). The optimum braking force is just below the locking limit, i.E. Shortly before the static friction changes to dynamic friction. In order to make the whole story calculable in spite of the many unknowns, certain calculation bases were simply established. "Lambda B" is called the ratio of existing to utilized coefficient of friction. At lambda B = 1 the wheel locks, at lambda B = 0 it is unbraked.
Furthermore you should keep in mind that the blocking order (first in front, then behind) must be kept, not only on level roads, but also on uphill and downhill roads, to keep the car controllable for Erna Normalhausfrau! Although it can be fun to collect the insects with the side windows instead of the front mask, inexperienced drivers may find a situation in which the rear of the vehicle suddenly breaks away rather threatening! In view of the above, a combination of disc brakes on the front axle and drum brakes on the rear axle is a cost-effective and viable solution, at least for everyday traffic.
Primitive brake systems (for example in the Rekord C and some Commodore A) still manage without brake pressure reducers and with correspondingly small rear wheel brake cylinders. At least on the Commodore A GS, GS 2800 and GS/E there were already larger wheel brake cylinders and a corresponding brake pressure reducer. With this braking system already clearly better values were to be obtained.
At Drum brake systems it is still to be taken into account that the self-increasing braking effect during braking is much more dependent on the friction values of the brake pads than, for example, disc brakes. Due to the design of the drum brake, it is better protected against mud and splash water, but various factors can drastically change the braking effect:
– Elongation of the drum due to temperature repair – Leaving the (narrow) manufacturing tolerances – Change in the coefficient of friction due to contamination (z. B. Brake dust) – (Depending on the construction principle also) driving direction
The Disc Brake has a number of advantages over the drum brake:
– Less dependence on friction values of the brake pads – Better dosing – Better braking performance – Same performance in both directions of rotation – Easier and faster pad replacement
Notable Disadvantages of the disc brake Compared to the drum brake should probably be essentially the higher unsprung masses. The higher actuating forces and the resulting mandatory brake booster are probably just as negligible as the higher wear and tear. However, these aspects clearly take a back seat to the higher safety of the disc brake.