This article is one in a series that have been released in conjunction with Wayne's book, 101 Projects for Your Porsche 911. The book contains 240 pages of full color projects detailing everything from performance mods to changing your brake pads. With more than 650+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any Porsche 911 owner's collection. See The Official Book Website for more details.
Over the years, the parking brake on your 911 may become unadjusted and fail to perform properly. The adjustment of the brake shoes is an easy process, and shouldn't take you more than an hour to accomplish.
The first step is to raise the rear of the car and remove the two road wheels. This will allow you access to the rear calipers. Make sure that the parking brake lever is released. Using a screwdriver, push back slightly on the brake pads until the brake disc is allowed to turn freely on its spindle. Be careful to check the fluid level in the master cylinder reservoir, as pushing the pads back will make the fluid level rise and may cause it to overflow.
Once the brake disc can be moved easily, loosen the two nuts that attach the handbrake cable to the inside of the brake mechanism. If there is any pretension on these cables, then it will be difficult to adjust the handbrake. The adjustment of the parking brake shoes is accomplished by turning a small gear or sprocket with a screwdriver. Unfortunately, this sprocket can only be reached through a small access hole in the brake disc.
Looking at your brake discs carefully, you will see a large hole in the disc. Rotate the brake disc until you can see the small adjusting sprocket through the hole. You may need a flashlight for this procedure. I recommend one with a narrow beam. Rotate the cog until the parking brake shoe is tight and the rotor can no longer be rotated. Depending on your year car, you may need to rotate the sprocket to the left or the right. (Approx location of the sprocket is near 4 o'clock for the left wheel and approx 8 o'clock for the right wheel). If you are turning the sprocket a lot, and the brake disc isn't tightening up, then you are probably turning it the in the wrong direction. Repeat this procedure for the opposite side of the car.
After you have the sprockets adjusted so that the brake shoes have just pressed up against the inside of the disc, tighten up the ends of the parking brake cables. Now, move to the cockpit of the car, and pick up the carpet that covers the rear of the handbrake/heater lever assembly. In the assembly housing, you will find two access holes, through which you will see a small lever that attaches to both parking brake cables. As you pull the lever, you should see this equalizer lever move. The purpose of this lever is to make sure that both sides of the parking brake receive equal amounts of force. When the parking brake handle is pulled up, the equalizer must be parallel with the axle of the car, otherwise one side of the parking brake will work better than the other. If the equalizer is skewed, then you will need to adjust the parking brake cables at the point where they screw into the rear of the brake assembly. Adjust the lengths of the two cables using the two adjusting nuts until the equalizer is parallel with the axles of the car.
After you have determined that the equalizer lever is properly set, make sure that you tighten up the two nuts against each other on the cables, located near the rear brake assemblies. Then, back off the parking brake adjusting sprocket (using a screwdriver, poking through the brake disc) about four to five teeth. Finally, check the proper operation of the handbrake. The brake discs should be free to rotate with the handle in the down position, but fully locked by the time that the handbrake is pulled up at least four clicks.
When you are finished, recheck the master cylinder reservoir, and also step on the brake pedal a few times in order to make sure that the pistons have repositioned themselves properly against the brake pads.
Removing the rotor reveals the mechanism for the parking brake adjustment. As the small cog is turned, the parking brake shoes are pushed outwards towards the inside of the disc. The proper adjustment of the shoes exists when the shoes are just about to touch the inside of the disc. Use this photo to identify the location of the sprocket when you are trying to look through the access hole in the brake disc.
Pulling up the carpet reveals the cable equalizer check holes (shown by the arrows). It is important that the equalizer be level (as shown here), otherwise your parking brake will not work properly. If the equalizer is not level, then you will need to adjust the parking brake cables where they attach to the rear of the brake assembly. Diagram 1: The 911 rear brake system utilizes a disc rotor for the main brakes, and a drum-type system for the parking brake. As this diagram shows, when the parking brake is pulled, the internal springs of the drum brake system press the brake shoes outwards towards the inside drum of the brake rotor. As the parking brake assembly expands to engage the inside brake drum contained within the brake discs, the force is transmitted to both shoes. Rotation of the wheels either forwards or reverse helps to increase the braking capacity of the mechanism by jamming the shoe into the inside drum part of the brake rotor. When properly adjusted, the design works quite well.