Brakes – Inspecting / Replacing Brake Rotors – 2.5L NA

Overview

This procedure guides you through inspecting and replacing the brake rotors on all Porsche 944 variants with an 8-valve engine configuration, covering both the older (1983–1985.5) and newer (1985.5–1988) variants. Regular inspection ensures rotors meet thickness and runout specifications for safe braking performance, while replacement addresses worn or damaged rotors to maintain optimal braking. The process differs slightly between the pre-1985.5 and 1985.5-onwards models, particularly for front rotor removal and installation, as noted below.

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

Tools Required

• Metric socket set (including 10mm (3/8 inch) and larger sizes)
• Metric wrench set (including 10mm (3/8 inch) and larger sizes)
• Jack stands
• 10mm Allen head socket (85.5 Onwards)
• Micrometer (for measuring rotor thickness)
• Dial indicator (for measuring rotor runout)
• Flat-tip screwdriver
• Shock cord or wire (for securing caliper)

Parts Required

• Front brake rotor (if replacing), 944 351 041 02
• Rear brake rotor (if replacing), 944 352 041 02
• Wheel bearing seal (Pre-85.5, if replacing), 999 113 426 41
• Countersunk screws (for rotor-to-hub attachment, if needed), 999 067 053 09

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
• Parking Brake Adjustment

Step-by-Step Procedure

Step 1: Prepare the Vehicle

1. Loosen the wheel lug nuts for the rotors to be inspected or replaced by turning them two full turns using a 19mm (3/4 inch) socket.
2. Raise the vehicle and secure it on jack stands at all four corners. Ensure the car is stable before proceeding.
3. Remove the lug nuts and front wheels to access the brake rotors.

Step 2: Inspect Brake Rotor Thickness

4. Using a micrometer, measure the brake rotor thickness at eight evenly spaced points within the braking surface area.
5. Compare measurements to the following specifications for your Porsche 944:

– Front Rotor: New thickness: 20.5mm (0.807 inches); Minimum after machining: 19.1mm (0.752 inches); Minimum thickness: 18.5mm (0.728 inches).

– Rear Rotor: New thickness: 20mm (0.787 inches); Minimum after machining: 19.2mm (0.756 inches); Minimum thickness: 18.6mm (0.732 inches).

6. If the rotor thickness is below the minimum, replace the rotor (see Steps 4–6).

Step 3: Inspect Brake Rotor Runout

7. Check the front and rear rotor runout as follows:

For front rotors:

– Follow this link to ensure this step – Front Wheel Bearings – Checking, Adjustment, Repacking, and Replacement – of the process is followed accurately to adjust front wheel bearing play.

– Follow this link to ensure this step – Brake Pads – Checking Thickness and Replacing Pads – of the process is followed accurately to remove the front brake pads.

– Attach a dial indicator to the brake caliper, positioning the pointer near the center of the rotor.

– Set the dial indicator to zero, then rotate the rotor by hand to measure runout. Lateral runout should not exceed 0.1mm (0.004 inches).

For rear rotors:

– Follow this link to ensure this step – Brake Pads – Checking Thickness and Replacing Pads – of the process is followed accurately to remove the rear brake pads.

– Attach a dial indicator to the brake caliper, positioning the pointer near the center of the rotor.

– Set the dial indicator to zero, then rotate the rotor by hand to measure runout. Lateral runout should not exceed 0.1mm (0.004 inches).

– If runout exceeds 0.1mm (0.004 inches), check wheel hub runout:

– Remove the rotor (see below Step 4 for rear rotors and front rotors).

– Measure hub runout with the dial indicator. Hub runout should not exceed 0.05mm (0.002 inches).

– If hub runout exceeds 0.05mm (0.002 inches), replace the hub (consult a professional or refer to Porsche 944 Workshop Manual).

– If hub runout is within limits, install thin shims (available from automotive suppliers) between the hub and rotor, or have the rotor resurfaced by a machine shop. If runout cannot be corrected, replace the rotor.

Step 4: Remove Rear Brake Rotor

8. Begin removing the rear brake rotor as follows:

– If equipped with steel trailing arms (Pre-85.5), remove the rear wheel spacer using a 19mm (3/4 inch) socket.

– If reusing the rotor, mark its orientation to the hub with a paint marker or scribe for proper reinstallation.

– Remove the countersunk screw (999 067 053 09) securing the rotor to the hub using a 6mm (1/4 inch) Allen head socket.

– Pull the rotor straight off the hub. If it resists:

– Insert a flat-tip screwdriver through the access hole in the rotor and adjust the parking brake to loosen it. Follow this link to ensure this step – Parking Brake Adjustment – of the process is followed accurately.

– If the rotor still does not come off, thread two 8mm bolts into the provided holes in the rotor. Alternately tighten the bolts to jack the rotor off the hub.

Step 5: Remove Front Brake Rotor

9. Remove the front brake rotor based on your model year:

For Pre-85.5 models:

– Follow this link to ensure this step – Brake Pads – Checking Thickness and Replacing Pads – of the process is followed accurately to remove the brake pads.

– Remove the two caliper retaining bolts (19mm, 3/4 inch) attaching the caliper to the steering knuckle. Slide the caliper off the rotor and hang it securely with shock cord or wire to avoid stressing the brake hose.

– Remove the dust cap on the front wheel hub using a flat-tip screwdriver.

– Loosen the Allen bolt on the clamping nut using a 6mm (1/4 inch) Allen head socket.

– Remove the clamping nut and slide the hub and rotor assembly off the front spindle. Note: The outer wheel bearing may fall out; set it aside carefully.

– If reusing the rotor, mark its orientation to the hub with a paint marker or scribe.

– Separate the rotor from the hub by removing the five retaining bolts using a 13mm (1/2 inch) socket.

For 85.5 Onwards models:

– Follow this link to ensure this step – Brake Pads – Checking Thickness and Replacing Pads – of the process is followed accurately to remove the brake pads.

– Remove the two caliper retaining bolts (19mm, 3/4 inch) attaching the caliper to the steering knuckle. Slide the caliper off the rotor and hang it securely with shock cord or wire.

– If reusing the rotor, mark its orientation to the hub with a paint marker or scribe.

– Remove the countersunk screws (999 067 053 09) attaching the rotor to the hub using a 6mm (1/4 inch) Allen head socket.

– Slide the rotor straight off the hub.

Step 6: Install Front Brake Rotor

10. Install the front brake rotor based on your model year:

For Pre-85.5 models:

– Attach the new or resurfaced front brake rotor (944 351 041 02) to the hub using the five retaining bolts. Tighten to 23 Nm (17 ft-lbs) using a 13mm (1/2 inch) socket.

– Ensure the inner wheel bearing is installed in the hub. If replacing, use a new bearing (consult Porsche 944 Workshop Manual).

– Install a new wheel bearing seal (999 113 426 41) in the hub using a seal driver or a socket matching the seal’s diameter.

– Slide the hub/rotor assembly onto the front spindle, feeling slight resistance as the seal engages.

– Check the grease packing on the outer wheel bearing. Slide the outer bearing onto the spindle and seat it into the hub.

– Follow this link to ensure this step – Front Wheel Bearings – Checking, Adjustment, Repacking, and Replacement – of the process is followed accurately to adjust the front bearing play.

– Slide the caliper onto the rotor and attach it to the steering knuckle with the retaining bolts. Tighten to 85 Nm (63 ft-lbs) using a 19mm (3/4 inch) socket.

– Follow this link to ensure this step – Brake Pads – Checking Thickness and Replacing Pads – of the process is followed accurately to install the brake pads.

For 85.5 Onwards models:

– Slide the new or resurfaced front brake rotor (944 351 041 02) onto the hub.

– Install the countersunk screws (999 067 053 09) to secure the rotor to the hub. Tighten to 10 Nm (7 ft-lbs) using a 6mm (1/4 inch) Allen head socket.

– Slide the caliper onto the rotor and attach it to the steering knuckle with the retaining bolts. Tighten to 85 Nm (63 ft-lbs) using a 19mm (3/4 inch) socket.

– Follow this link to ensure this step – Brake Pads – Checking Thickness and Replacing Pads – of the process is followed accurately to install the brake pads.

Step 7: Install Rear Brake Rotor

11. Install the rear brake rotor as follows:

– Place the new or resurfaced rear brake rotor (944 352 041 02) onto the hub, aligning any marked orientation if reusing the rotor.

– Install the countersunk screw (999 067 053 09) to secure the rotor to the hub. Tighten to 10 Nm (7 ft-lbs) using a 6mm (1/4 inch) Allen head socket.

– Follow this link to ensure this step – Parking Brake Adjustment – of the process is followed accurately to adjust the parking brake.

– Slide the caliper onto the rotor and attach it to the trailing arm with the retaining bolts. Tighten to 85 Nm (63 ft-lbs) using a 19mm (3/4 inch) socket.

– Follow this link to ensure this step – Brake Pads – Checking Thickness and Replacing Pads – of the process is followed accurately to install the rear brake pads.

– If equipped with steel trailing arms (Pre-85.5), reinstall the rear wheel spacer using a 19mm (3/4 inch) socket.

Step 8: Finalize Installation

12. Complete the installation as follows:

– Reinstall the wheels and tighten the lug nuts to 130 Nm (96 ft-lbs) using a 19mm (3/4 inch) socket in a star pattern.

– Lower the vehicle from the jack stands and fully tighten the lug nuts again to ensure proper seating.

Post Procedure Checklist

• Verify all bolts (caliper, rotor, and lug nuts) are tightened to the specified torque values.
• Check that the brake pads are properly installed and seated.
• Test the parking brake for proper engagement after adjustment.
• Spin each wheel by hand to ensure it rotates freely without dragging.
• After a short test drive of 5 miles (8 km), check for unusual noises, vibrations, or brake pulsation, which may indicate improper installation or rotor issues.

Sources

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