Brakes – Inspecting / Replacing Brake Rotors

Overview

This guide explains how to inspect and replace the brake rotors on your Porsche 944 with a 16v engine. Regular inspection ensures your brakes perform safely, while replacement is needed if rotors are worn beyond their minimum thickness or show excessive runout. This process is crucial for maintaining stopping power and vehicle safety.

Pink and blue text represents links to additional resources, tools, parts, and partner websites.

Tools Required

• Metric socket set
• Metric wrench set
• Jack stands
• 10mm (3/8 inch) Allen head socket
• Micrometer
• Dial indicator
• Flat tip screwdriver
• Shock cord or wire (to hang calipers)

Parts Required

• Front brake rotor –944 351 041 06 (if replacement is needed)
• Rear brake rotor –944 352 041 02 (if replacement is needed)
• Countersunk screws for rotor attachment (front and rear) – reuse or replace if damaged

Required Additional Procedures

Steps in these procedures are required to complete this process:

• Brake Pads – Checking Thickness and Replacing Pads
• Front Wheel Bearings – Checking, Adjustment, Repacking, and Replacement

Step-by-Step Procedure

Step 1: Inspecting Brake Rotors

1. Loosen the wheel lug nuts on the front and rear wheels by turning them two full turns with a lug wrench.
2. Lift the Porsche 944 using a jack and secure it on jack stands at all four corners.
3. Finish removing the lug nuts and take off the front and rear wheels.
4. Measure the thickness of the front brake rotors using a micrometer. Check eight spots within the braking surface area. For the 944, new front rotor thickness is 28 mm (or 32 mm for cars with option M758), minimum thickness after machining is 26.6 mm (30.6 mm with M758), and minimum thickness is 26 mm (30 mm with M758).
5. Measure the thickness of the rear brake rotors using a micrometer. Check eight spots within the braking surface area. For the 944, new rear rotor thickness is 24 mm, minimum thickness after machining is 22.6 mm, and minimum thickness is 22 mm.
6. To check front rotor runout, adjust the front wheel bearing play. Follow this link to ensure this step – Front Wheel Bearings – Checking, Adjustment, Repacking, and Replacement – is followed accurately.
7. Remove the front brake pads. Follow this link to ensure this step – Brake Pads – Checking Thickness and Replacing Pads – is followed accurately.
8. Attach a dial indicator to the front brake caliper, set it to zero, and place the pointer near the center of the rotor. Turn the rotor by hand and check the runout. It should not exceed 0.1 mm.
9. For the rear rotors, remove the rear brake pads. Follow this link to ensure this step – Brake Pads – Checking Thickness and Replacing Pads – is followed accurately.
10. Attach a dial indicator to the rear brake caliper, set it to zero, and place the pointer near the center of the rotor. Turn the rotor by hand and check the runout. It should not exceed 0.1 mm.
11. If runout exceeds 0.1 mm on either front or rear rotors, check the wheel hub runout by removing the rotor (see Step 2 or 3 below). Hub runout should not exceed 0.05 mm. If it does, replace the hub. If hub runout is within limits, reduce rotor runout with thin shims between the hub and rotor, or have a machine shop resurface the rotor. Replace the rotor if runout cannot be corrected.

Step 2: Removing the Front Brake Rotors

12. Remove the front brake pads. Follow this link to ensure this step – Brake Pads – Checking Thickness and Replacing Pads – is followed accurately.
13. Remove the two caliper retaining bolts attaching the caliper to the steering knuckle using a wrench. Slide the caliper off the rotor and hang it out of the way with shock cord or wire.
14. If reusing the rotor, mark its orientation to the hub with a marker or chalk.
15. Remove the countersunk screws attaching the rotor to the hub using a 10mm (3/8 inch) Allen head socket.
16. Slide the rotor straight off the hub to remove it.

Step 3: Removing the Rear Brake Rotors

17. If reusing the rotor, mark its orientation to the hub with a marker or chalk.
18. Remove the countersunk screw holding the rotor to the hub using a 10mm (3/8 inch) Allen head socket.
19. Try pulling the rotor straight off the hub by hand.
20. If it doesn’t come off, insert a flat tip screwdriver through the access hole in the rotor and adjust the parking brake to loosen it.
21. If the rotor still won’t budge, thread two bolts into the provided holes in the rotor. Turn each bolt several turns alternately to jack the rotor off the hub.

Step 4: Installing the Front Brake Rotors

22. Slide the new or resurfaced front brake rotor (944 351 041 06) onto the hub.
23. Secure the rotor to the hub with the countersunk screws using a 10mm (3/8 inch) Allen head socket.
24. Slide the brake caliper onto the rotor and attach it to the steering knuckle with the retaining bolts. Tighten to 85 Nm (63 ft-lbs) using a torque wrench.
25. Install the front brake pads. Follow this link to ensure this step – Brake Pads – Checking Thickness and Replacing Pads – is followed accurately.

Step 5: Installing the Rear Brake Rotors

26. Place the new or resurfaced rear brake rotor (944 352 041 02) onto the hub.
27. Secure the rotor to the hub with the countersunk screw using a 10mm (3/8 inch) Allen head socket.
28. Slide the brake caliper onto the rotor and attach it to the trailing arm with the retaining bolts. Tighten to 85 Nm (63 ft-lbs) using a torque wrench.
29. Install the rear brake pads. Follow this link to ensure this step – Brake Pads – Checking Thickness and Replacing Pads – is followed accurately.

Post Procedure Checklist

• Ensure all bolts are tightened to the correct torque (e.g., caliper bolts to 85 Nm (63 ft-lbs)).
• Check that the rotors spin freely without excessive wobble or noise.
• Verify parking brake adjustment allows smooth rotor movement (rear only).
• Test drive the vehicle for 5 miles (8 km) at low speed to confirm brake performance.

Sources

• Clark’s Garage
• Pelican Parts
• Porsche 944 Workshop Manual, Volume 1
• Youtube