9850043 R01 - 2017-2021
RANGER
500 / 570 Service Manual
© Copyright Polaris Inc.
10.5
HYDRAULIC BRAKE SYSTEM OPERATION
The 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.
Summary of Contents for RANGER 500 2017
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