Hydraulic Brake System - Overview Of Operation - Polaris RZR 170 2009 Service Manual

BRAKES

HYDRAULIC BRAKE SYSTEM - OVERVIEW OF OPERATION

The Polaris brake system consists of the following components or assemblies: brake pedal, master cylinder, master cylinder fluid
reservoir, hydraulic brake lines, brake calipers, brake pads, and brake discs, which are secured to the drive line.
When the brake pedal is applied, the master cylinder piston is forced inward. As piston moves inward, pressure is created in the
separate and sealed front and rear brake chambers inside the master cylinder. Pressure travels through the front and rear brake lines
and then to the pistons inside the brake calipers. The caliper pistons are forced outward against the moveable brake pad. When the
pad contacts the brake disc, the floating caliper bracket moves to force the stationary brake pad against the disc, and the resulting
friction reduces brake disc and vehicle speed.
As brake pads wear normally from friction, the caliper pistons move outward to compensate. Fluid from the master cylinder reservoir
fills the additional volume created in the caliper body as the pistons move outward (self adjusting feature).
Fluid level in the reservoir is a critical maintenance item. If fluid level gets too low, air could enter the system and cause poor brake
performance or even brake system failure. If the fluid level is too high, pressure could build in the brake system causing the brake
pads to drag due to fluid expansion.
Brake fluid and brake system parts expand and contract due to the heating and cooling during normal operation. A very small hole
called the compensating port, located inside the master cylinder, is opened and closed by the master cylinder piston. When the brake
pedal is released, the piston returns to its rest position and the compensating port is open. This allows expanding or contracting fluid
to move back and forth between master cylinder and fluid reservoir, preventing a buildup of pressure in the system.
It is very important that the master cylinder reservoir have adequate space to allow for fluid expansion. Never overfill the reservoir.
Do not fill it beyond the MAX LEVEL line!
When servicing Polaris brake systems use only Polaris DOT 4 Brake Fluid (PN 2872189). WARNING: Once a bottle is opened,
use what is necessary and discard the rest in accordance with local laws. Do not store or use a partial bottle of brake fluid. Brake
fluid is hygroscopic, meaning it rapidly absorbs moisture. This property is desirable in order to reduce the chance of corrosion (due
to moisture) in the brake system. But an open container of fluid will absorb moisture from the environment. When brake fluid contains
moisture the boiling point is reduced, which can lead to early brake fade and the possibility of serious injury. Brake fluid must be
changed with fresh fluid from a sealed container at recommended intervals or if contaminated.
BRAKE SYSTEM - MECHANICAL COMPONENTS
Brake System - Mechanical Components
Brake Light Switch Spring
Pedal Return Spring
6.4
12 ft-lb
(16 Nm)
Parking Brake Cable Parking Brake Switch