Disk Brake Maintenance; The Hydraulic System; Maintenance Tasks; Linkage Adjustment - Royal Enfield Bullet RES 500 Service Manual

CHAPTER 5 APPENDIX
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THE DISC BRAKE
DISK BRAKE MAINTENANCE
Disk Brakes although not really ever requiring adjustment as with drum brakes
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lining wear is compensated for
by an added fluid demand
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do require regular and careful maintenance of a different kind. This involves the
hydraulic systems o r puck replacement.
The Hydraulic System
The master cylinder is a simple hydraulic pump. A piston in the cylinder is retracted back by the return spring, far
enough t o expose a port from the reservoir to the cylinder. When the control
is
operated, the piston moves forward
in the cylinder, first closing off the port, and then compressing the fluid in the cylinder. This fluid is forced under pressure
t o the brake cylinder(s), in which it forces the pistons outward against the friction pucks, which exert a squeezing
force on the rotating disk, mounted on the wheel hub. The force exerted by the hand or foot is multiplied considerably
by hydraulic "leverage," since a relatively large control movement is translated into very little puck movement at the
wheel hub. Releasing the control allows the master cylinder return spring to return the piston to the retracted position,
thus releasing the pressure on the pucks, and the brake action ceases. In addition, the intake port of the master
cylinder once again becomes exposed to the reservoir, and the cylinder "recharges" with more fluid, if necessary.
For this reason, the brake may be "pumped up" if necessary
-
providing there's enough fluid in the reservoir.
The Line
The hydraulic line from master cylinder must have a flexible link, due t o the suspension movement of the wheels
relative t o the frame o r handlebar. Thus, as well as steel tubing, the line system has a neoprene hose section
inserted in the run.
The Caliper
The calipers which surrounds the brake disk, responds t o the supply of master cylinder pressure by providing a
squeezing force t o the disk. This force is generated by the action of a piston in a shallow cylinder of consider-
ably larger bore than that of the master cylinder. Thus a relatively long and low-force stroke of the small-diame-
ter master cylinder piston results in a much higher-force and shorter stroke of the caliper piston. Calipers in
some models are "floating," using only one piston and cylinder t o exert force, with the opposite force being pro-
vided by floating action of the other side of the caliper being allowed t o move on the mounting bolts. Most,
however, use dual piston/cylinder arrangements, with a piston for each puck.
MAINTENANCE TASKS
Linkage Adjustment
The linkage from control to master cylinder is adjustable by means of an adjusting screw, held in place by a lock-
nut. To check adjustment, operate the control, ensuring that there is just a little free play of the lever before
engagement with the master cylinder. To adjust, loosen the locknut, adjust the play, and tighten the locknut. D o
not overtighten, but be sure to tighten it enough so that
it
won't come loose in service
-
and be sure t o monitor
the "feel" as you ride
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if it gets too loose o r tight, stop and set
it
up.
Linkage adjustment is not required to compensate for lining wear. As the linings wear, more fluid moves t o the
wheel cylinder from the master cylinder reservoir. Consequently, as wear occurs, addition of fluid may be required.
The Enfield BULLET MANUAL by Pete Snidal O 2002 APPENDIX I