When braking, the oil is pressed into the inner and outer wheel cylinders, and its piston presses the two brake pads against the brake disc under the hydraulic pressure, resulting in friction torque and braking. At this time, the edge of the rectangular rubber seal ring in the wheel cylinder groove produces a small amount of elastic deformation under the action of the piston friction. When the brake is released, the piston and the brake pad rely on the elastic force of the seal ring and the elastic force of the spring to return to position.
Because the deformation of the edge of the rectangular sealing ring is very small, it is enough to ensure the release of the brake when the brake is not applied. And because the thickness of the brake disc expands only slightly when heated, the phenomenon of "stagnation" will not occur. In addition to the sealing function, the rectangular rubber sealing ring also plays the role of piston return and automatic clearance adjustment.
If the gap between the friction lining of the brake pad and the disc wears more, after the deformation of the sealing ring during braking reaches the limit, the piston can continue to move until the friction lining presses the brake disc. After the brake is released, the distance that the rectangular rubber seal pushes the piston back is the same as before the wear, and it still maintains the standard value.
