This is part of my Brief Guide To Brakes series – a result of my research for Edinsolar, the University of Edinburgh’s solar vehicle team.
HOW IT WORKS
• Hydraulic piston pushes calipers together
• The calipers press the brake pads against the disc
• Friction from the pads slows the disc
• The wheel slows down
The piston has a seal called the square-cut seal that becomes twisted when dragging and stretching along while the piston moves in and out but returns to its original shape when the brakes are released.
VARIATIONS
The calipers can be forced together mechanically, hydraulically, pneumatically or electromagnetically.
The discs can be:
vented
– hollowed with fins and vanes to cool
cross-drilled
– holes drilled in the sides of the discs to cool and remove water
– can be the source of stress cracks under severe conditions
slotted
– shallow channels are machined into the disc to help remove gas, dust and water
– wears down the brake pads – removing material keeps them soft and prevents vitrification or glazing of the brake pads, especially in a racing environment
Often the discs are made from cast iron, particularly a type called Grey Iron, but in racing most cars use reinforced carbon and in some very niche vehicles, ceramic composites.
