Why bleed your brakes

BLEEDING Whilst there is some 'mystery' about this, it is basically a simple operation. The objective is to ensure that all air is purged out of the system(s) so that only good, fresh brake fluid is in the calipers, master cylinders, pipe-work and hoses.

Air must be removed from the hydraulic system because it is compressible whereas brake fluid is not. The absence of compressability gives the firm pedal that we require. In order to achieve that 'good', firm pedal, it is advisable to check the brake pipes & hoses to ensure that there are no vertical loops in which air could be trapped. For the same reason this is why, with racing calipers, the bridge pipe connecting the two sides of a caliper, is always at the bottom with the bleed screws at the top. On race or rally cars with dual systems (front & rear), it is essential that both systems are bled simultaneously.

When bleeding is complete, ensure that bleed screws are 'torqued' to 14 Nm when the system is cold - or 18Nm if hot (at the track). Remove any signs of fluid from around the bleed screws and calipers.