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9.4
BRAKES
9923142 - 2011 RANGER RZR / RZR S / RZR 4 Service Manual
© Copyright 2010 Polaris Sales Inc.
HYDRAULIC BRAKE SYSTEM OPERATION
The Polaris brake system consists of the following components or assemblies: brake pedal, master cylinder, hydraulic brake lines,
brake calipers, brake pads, and brake discs, which are secured to the drive line.
When the foot activated brake lever is applied it applies pressure on the piston within the master cylinder. As the master cylinder
piston moves inward it closes a small opening (compensating port) within the cylinder and starts to build pressure within the brake
system. As the pressure within the system is increased, the pistons located in the brake calipers move outward and apply pressure
to the moveable brake pads. These pads contact the brake discs and move the calipers in their floating bracket, pulling the stationary
side pads into the brake discs. The resulting friction reduces brake disc and vehicle speed.
The friction applied to the brake pads will cause the pads to wear. As these pads wear, the piston within the caliper moves further
outward and becomes self adjusting. Fluid from the reservoir fills the additional area created when the caliper piston moves outward.
Brake fluid level is critical to proper system operation. Too little fluid will allow air to enter the system and cause the brakes to feel
spongy. Too much fluid could cause brakes to drag due to fluid expansion.
Located within the master cylinder is the compensating port which is opened and closed by the master cylinder piston assembly. As
the temperature within the hydraulic system changes, this port compensates for fluid expansion or contraction. Due to the high
temperatures created within the system during heavy braking, it is very important that the master cylinder reservoir have adequate
space to allow for fluid expansion. Never overfill the reservoir! Do not fill the reservoir 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 causes the boiling temperature of the brake fluid to drop, which can
lead to early brake fade and the possibility of serious injury.