Welcome to the first of the car enthusiast's more technical articles. Please send all comments and suggestions to Shane directly by email.

Traditional brake systems

In virtually every current production car, the brakes still operate using the age-old (some would say tried and tested) method of hydraulic actuation. Pure mechanics are brought into force, with several advantages such as working brakes even after engine failure, and simplicity.

The schematic above shows the basic layout. The driver pushes the brake pedal, generating hydraulic pressure in the master cylinder that is transmitted to the actuators at each wheel through the brake lines, thus applying the brakes. Going a little deeper, the 'vacuum booster' shown above utilises the below-atmosphere pressure of the inlet manifold to magnify the driver's input. The actuators vary depending on the type of brakes.

The average modern car utilises front disk brakes and rear drum brakes, although there is a trend towards four-wheel disk brakes. With disk brakes high pressure brake fluid forces the piston out and at the same time forces the whole brake caliper back to cause both pads to contact the disk itself. The caliper "floats" on the caliper pin. When the brakes are released, the hydraulic pressure drops. The low residual pressure allows the seal to draw the piston back thus releasing the disk. The seal twists and deforms when the brakes are applied and it is the recovery from this deformed state which causes the piston and pads to release.

Most systems allow some pad drag even when the brakes are released however. Note that the piston can also slide through the seal providing a self adjusting action to compensate for pad wear.

Mechatronics

It is quite obvious that many components make up this system. Why not have completely electonic control? This may eventually be possible, although legislation will probably be the most substantial hurdle. For instance, what if your electrical system fails? No brakes! There is a bridge between the two methods however - "mechatronics". This is very much a buzzword in the car industry at the moment, but it isn't really a new concept. The areas in which it is to be applied may well be novel however. For instance, Mercedes-Benz new 'Sensotronic Brake Control', which we will refer to as SBC.

The SBC concept

More later - we better give you time to digest that much!