We replace the sealing ring if there are traces of brake fluid leakage in the brake mechanism.
We show the replacement of the boot and the sealing ring on the brake cylinder of the front wheel. The cover and sealing ring on the brake cylinder of the rear wheel are replaced in the same way.
We remove the front wheel.
Disconnect the lower end of the brake hose from the caliper (see Replacing the front wheel brake hose).
Removing brake pads (see Replacing the brake pads of the front wheels).
Using a 14mm wrench, unscrew the upper bolt securing the caliper to the guide pin..
... and remove the caliper.
Remove the piston from the caliper.
To remove the piston, you can apply compressed air from the tire pump through the hole in the caliper.
Remove the protective cover from the caliper.
We pry off the sealing ring with a screwdriver..
... and remove the ring from the caliper.
Install a new sealing ring. We insert a new protective cover into the groove of the caliper.
We apply brake fluid to the working surface of the sealing ring and the surface of the piston. To install the piston, we clamp the caliper in a vice with soft metal jaw pads. In order to put a protective cover on the piston, we attach the tire pump or compressor hose to the caliper hole.
We supply air to the cylinder and bring the piston bottom to the edge of the cover, centering it relative to the cover.
Under the action of air pressure, the cover is straightened and put on the piston inserted into the cylinder.
In the absence of a pump, an assistant will be required to put the cover on the piston, who must lift the cover by the edge (inserted into the groove of the caliper) and stretch it so that the piston can be inserted inside.
Having put on the cover, we center the piston..
... and, pressing on it with a wooden block, we sink the piston into the caliper.
We assemble the brake mechanism in reverse order.
Bleeding the hydraulic brake system (see Bleeding hydraulic brake system).