Front Brake Disc Replacement

Removing and Installing Front Brake Disc


Removal

1. Take off front wheel.

2. Separate brake pipe from brake hose at the spring strut and remove brake caliper. First press down brake pedal with pedal holder to prevent brake fluid from escaping from the reservoir.
Cover or plug brake hose and brake pipe (to avoid dirt ingress). Remove retaining spring from brake hose.

3. Take off brake disc after undoing the countersunk head screw(s). If a stiff brake disc cannot be released even by applying light blows with a plastic hammer, screw hexagon head bolts simultaneously into the M8 threads of the brake disc and press off brake disc.

Important Note





The front brake discs of the 911 Turbo are a two-part assembly.
Brake disc No.1 is bolted to the ring (cup) No.2 with 10 bolts No.3 (M 6). Only the complete brake disc assembly (disc with ring) is available as a spare part.
Important: Do not separate brake disc holder and brake disc. Furthermore, turning the screws no.3 (even if they seem to be loose) is neither permitted nor required [for explanation about Tightening, Play (A), and Gap (S) refer to Explanation Pertaining to Two-Piece Brake Disc.]


Explanation Pertaining to Two-Piece Brake Disc

The brake disc coming in two pieces for reasons of noise suppression is the result of further development and optimization. The play between the brake disc flange and the contact surface of the screw head may be 0 - max. 0.1 mm depending on the tolerances. (dimension A in figure).

In spite of a correct tightening torque (8 Nm/ 6 ftlb.) it may occur that the screw including the bushing can be turned by a few angular degrees. The angle results from the gap "S" between bushing and brake disc holder which is subject to tolerances. This may lead to the misinterpretation of a "loose screw". However, pinching prevents the screw from turning in the bushing.

Never change the tightening torque of the 10 screws (do not turn the screws) as this might have negative effects on noise emissions.


Installation

1. Check all parts for serviceability and replace if required.

2. Clean mating and centering surfaces of brake disc and wheel hub. Coat centering surface of wheel hub with a thin coat of Optimoly TA.

3. Fit brake disc.

Note
Take care not to mix up right and left hand brake discs during reassembly.
Identification: Involute shape and Part No.
The Part No. is indicated on the brake disc.

Spare part for LH side - 3rd group number: odd number
Spare part for RH side - 3rd group number: even number

Example:
Part No. of left-hand brake disc: 993.351 .045.10
Part No. of right-hand brake disc: 993.351.046.10

4. Fit brake caliper. Tighten new bolts of brake caliper to 85 Nm (64 ftlb.).
Check for correct routing of brake hose and brake pipe.
Bleed front brake circuit.

Note
Replace the mounting bolts (front axle only) after each dismantling operation.
The brake caliper mounting bolts for the front axle are 5 mm longer than those of the 911 Carrera (993).
The bolts are identified by differing colors.
911 Turbo (993) = red.
911 Carrera (993) = silver.