Yamaha YFM70RY Service Manual page 15

When the brake pedal is operated, the brake fluid pressure in the master cylinder increases and the
brake caliper piston "1" and the nut "2" are pushed.
When there is proper clearance between the brake caliper piston and the brake pad, no other parts
move because the movement of the brake caliper piston and the nut is absorbed by the backlash of the
threads of the nut and the adjusting bolt "3".
When the movement of the nut is greater than the backlash between the nut and the adjusting bolt, the
parking brake adjusts automatically.
The amount of the adjustment varies with brake fluid pressure. Operating the parking brake makes no
adjustment.
The adjustment operation is as follows.
1. When the brake pedal is operated, the brake fluid pressure increases and the brake caliper piston
and the nut move.
2. When the movement of the brake caliper piston and the nut is greater than the backlash of the
threads of the nut and the adjusting bolt, the force "A" will be required to pull the adjusting bolt.
The force to pull the adjusting bolt will be turned into the rotation torque "B" by the shape of the
threads of the nut and the adjusting bolt.
3. At this time, the clutch torque "C" between the adjusting bolt and the adjusting bolt sleeve "4" will
decrease depending on the force required to pull the adjusting bolt.
When the rotation torque exceeds the clutch torque, the adjusting bolt rotates and the clearance be-
tween the brake caliper piston and the brake pad decreases by the movement of the threads of the
nut and the adjusting bolt.
1. Brake caliper piston
2. Nut
3. Adjusting bolt
4. Adjusting bolt sleeve
1 2
1-6
A
B
3
C
FEATURES
4