Page 489 - Manual_Polaris_RZR_ProXP-20-21

BRAKE SYSTEM

BRAKE SYSTEM SERVICE NOTES • Make sure atmospheric vent on reservoir is
Disc brake systems are light weight, low maintenance, unobstructed.
and perform well in the conditions this vehicle will • Test for brake drag after any brake system service and
routinely encounter. There are a few things to remember investigate cause if brake drag is evident.
when replacing disc brake pads or performing brake
system service to ensure proper system function and • Make sure caliper moves freely on guide pins (where
maximum pad service life. applicable).
• Inspect caliper piston seals for foreign material that
• DO NOTover-fill the master cylinder fluid reservoir.
could prevent caliper pistons from returning freely.
• Make sure the brake pedal returns freely and • Perform a brake burnishing procedure after installing
completely.
new pads to maximize service life.
• Adjust stop pin on brake caliper(s) after pad service.
• DO NOT lubricate or clean the brake components with
• Check that the rubber baffle is retracted inside master aerosol or petroleum products. Use only approved
cylinder reservoir cap. brake cleaning products.
• Check and adjust master cylinder reservoir fluid level
after pad service.

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).
10
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.

9930583 R01 - 2020-2021 RZR PRO XP / XP 4 Service Manual 10.11
© Copyright Polaris Industries Inc.