Bleeding Brakes! How they work.

I had a reason to bleed my brakes on Sunday, a task which is easy....if you know how. However as with many things, there is a knack and for the mechanically challenged (but strangely willing to try) this is it in easy bite sized bits:

FIrst of all, how do brakes work? Well, the braking system on a car works by hydraulics. This means when you press the brake pedal the movement of the pedal is linked by a lever to a piston just behind the bukhead of the driver's footwell. (This is called the master cylinder.)

This piston is linked to a series of pipes which connect to another cylinder at the braking system on each wheel of your car. The force applied by your foot on the pedal is transferred through some liquid in some pipes to the braking system at the wheels. At each wheel the other piston moves in relation to the the 'master cylinder'.

The clever part is this: The master cylinder is narrower than the slave cylinders and this means that the force applied at the master cylinder is magically magnified at the slave cylinders so that your poor weak leg muscle is able to make a superman sized force on the brakes. Enough to make the car stop. Without this 'Hydraulic Advantage' you would not be strong enough to stop the car.

Here is a great article about the workings of car braking systems: