How to Rebuild a Polaris Sportsman Brake Caliper

Poor braking performance plus faster-than-usual brake pad wear are clear signs that the brake calipers on your Polaris ATV need a rebuild. It could be a leaking piston seal or dirty, sticking caliper slide pins, but whatever it is, a rebuild of the brake calipers is in order. 

Watch the video above and follow the steps below to rebuild a brake caliper on a Polaris Sportsman 850 XP.

Tools and Supplies – Polaris Sportsman ATV Brake Caliper Rebuild

  • 15mm wrench
  • 1/2" wrench
  • 5mm Allen
  • Punch tool
  • Hammer

Polaris ATV brake caliper inner seal

Polaris ATV brake caliper outer seal

NOTE: We rebuilt the front brake caliper on a Polaris Sportsman, but the rear calipers are almost identical and the steps are the same.

Disassembling Polaris Sportsman 850XP Brake Caliper

Step 1. Remove the wheel.

Step 2. Remove the 5mm Allen cap from the rear of the caliper.

Polaris Sportsman brake caliper removal

Step 3. Compress the brake piston back into the caliper by inserting a flathead screwdriver between the caliper and the outer brake pad, and levering against the caliper.

Polaris Sportsman 850 brake caliper removal

Step 4. Remove the half-inch banjo bolt securing the brake line to the caliper. 

Polaris Sportsman ATV brake caliper removal

NOTE: Don't lose the crush washers on either side of the brake line banjo fitting, and have a container ready to catch the brake fluid that will drain from the detached brake line.

Step 5. Remove the two 15mm brake caliper mounting bolts, and slide the caliper assembly off the brake disc.

Polaris ATV brake caliper removal

Polaris Sportsman 850 ATV brake caliper removal

Step 6. Remove the brake pads, and slide the caliper mount off from the caliper body.

Polaris Sportsman 850 ATV brake pads removal

Polaris brake caliper removal

Step 7. Position a punch tool through the back of the caliper and gently tap the piston out from the caliper. Inspect the piston for scratches or pitting and replace it if necessary.

Polaris Sportsman 850XP brake caliper rebuild

Polaris Sportsman 850XP brake caliper piston removal

Step 8. Inspect the two rubber boots that protect the caliper mount’s slide pins, and replace the boots if they’re split or worn.

Polaris Sportsman ATV brake caliper boot

NOTE: The rubber boots are different, so make sure you get one of each when replacing them.

Step 9. Remove the two piston seals from within the caliper bore. Use contact/brake cleaner to clean the channels the piston seals sit in and make sure there’s no dirt or debris within the caliper.

Polaris Sportsman brake caliper rebuild piston seals

Rebuilding Polaris Sportsman 850XP Brake Caliper

Step 1. Smear the new piston seals with DOT 4 brake fluid and install them into the caliper.

Polaris Sportsman brake caliper piston seal install

Polaris Sportsman 850 brake caliper piston seal install

PRO TIP: Don’t reuse old piston seals, even if they appear to be in good condition. New seals are inexpensive and it’s recommended to install new ones while the caliper is disassembled.

Step 2. Smear the piston with DOT-4 brake fluid and reinstall it into the caliper bore.

Polaris Sportsman 850 brake caliper piston installation

Step 3. Clean the caliper mount, grease the mount’s slide pins and reinstall the mount to the caliper body. Use a pick tool to hook the rubber boots back over the ridges on the slide pins so the boots are sealing and protecting the pins.

Polaris Sportsman 850XP ATV brake caliper rebuild

Polaris ATV brake caliper rebuild

Step 4. Reinstall the brake pads, or install a new set of brake pads.

Polaris Sportsman brake pads installation

Step 5. Slide the caliper assembly back over the brake disc, then reinstall the two caliper mounting bolts and the 5mm Allen cap.

Polaris 850 Sportsman brake caliper rebuild assembly

Step 6. Reinstall the wheel brake line, pair of crush washers and the half-inch banjo bolt.

Sportsman 850 brake caliper rebuild

Step 7. Reinstall the wheel and you’re done with one side.

After rebuilding the brake caliper on one side of your Polaris Sportsman, you need to repeat the process on the other side. Rebuilding the caliper only on one side leads to uneven braking and poor handling from your quad.

Once the brake calipers are rebuilt, you need to bleed the brake system. Watch our Polaris Sportsman 850XP brake bleed video above to see how it’s done.



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