Subject: Got Squealing Brakes?
   by Larry Reynolds
   Brake pad squeal is one way to warn other drivers that you and your
   Porsche are about to arrive. If you make enough noise, they think they
   are about to become intimate with a runaway garbage truck (pedestrians
   will yank small children back from the curb).
   There are several factors that cause brake squeal. The primary reason
   is usually the brake pads themselves. Many of the carbon metallic
   brake pads, such as Cool Carbon, etc. are the worst as far as
   squealing. This is due to the composition of the pad material itself.
   The stock Porsche pads are usually relatively quiet in comparison.
   Thus, the solution may be as simple as changing to a different brand
   of brake pad. Excessive brake pad wear, warped rotors, misaligned
   calipers, loose calipers, loose wheel bearings, incorrectly sized
   pads, glazed pads or rotors and sticky pistons may also cause your
   brakes to sing high alto in the anvil chorus.
   If your brake pads and braking system are in good condition and you
   experience squeal just as you are almost stopped, this is usually the
   brake pad vibrating against the rotor/caliper, causing the rotor to
   ring like a bell. If you experience noises at other times, check to
   make sure your brake pads are in good condition and show equal wear.
   Sometimes a piston will hang up and cause excessive wear and failure
   of one pad. Check all of your pads to make sure that one is not down
   to the metal backing plate. The backing plate does not have quite the
   coefficient of friction as do the brake pads and will usually dig
   nasty grooves into your rotor for good measure. If you experience
   clunking noises, a vibrating pedal, or a screeching sound, you should
   have your entire brake system checked by a qualified mechanic. If you
   wait too long, the next sound you hear may be "crash."
   One option to help reduce the brake pad symphony is to install brake
   pad vibration damper pads. The vibration dampers that Porsche and
   several other suppliers sell are a self-stick fiber material that
   adheres to the back of the brake pad backing plate. Some models are
   manufactured with a mushroom shaped button spring in the center. The
   button spring fits tightly into the piston and the fiber disk adheres
   to the backing plate of the pad. The theory is that the fiber disk
   will help cushion (i.e., soften) the vibration of the brake pad. The
   second part of the theory is the mushroom button will help pull the
   pad away from the rotor when the piston retracts after the brake is
   released. This resulting extra clearance will reduce/eliminate squeal.
   Sometimes they work, sometimes they don't.
   A second option is to coat the back of the brake pads with a quality
   anti-squeal compound. Wurth make a couple of nice ones. Wurth
   Anti-Squeal Spray (#890106) is an aerosol spray that puts a thick
   heat-resistant polymer adhesive on the back of the pad to cushion the
   pad from the caliper pistons and help the pad retract with the piston.
   A second option is Wurth DBQ -2200 (#8931102) that comes in a can with
   a top that looks like a liquid shoe polish bottle. This is applied to
   the back of the brake pad like a shoe polish. I have found that a
   combination of the Porsche vibration dampers and a coating of one of
   the brake anti-squeal compounds usually reduces low speed squeal to a
   tolerable level. (At least parents stop yanking their children back
   from the curb.)
   A third solution is to coat the area of the pad backing plate that
   contacts the caliper piston with a THIN coating of high temperature
   anti-seize. You do not have to coat the entire backing plate, only the
   area that is in contact with the piston. The key words are THIN and
   HIGH temperature. You do not want anti-seize to run onto the front of
   the pads or the rotor. This is somewhat like waxing your brake pads. I
   use Wurth CU1100 (#8938132) that resists temperatures up to 2000
   degrees and apply small circles to the piston contact area. This is
   not as effective as the above, but allows for quick changing of the
   brake pads.
   The type of driving and resulting braking requirements will usually
   determine the best solution for you. I use anti-seize on my track car
   where the brakes are used heavily and the pads are changed very
   frequently. On a street driven Porsche you may wish to consider the
   combination of pad silencers and anti-squeal compound. I can not over
   emphasize the importance of maintaining your braking system in top
   notch condition. If you are not confident in your brake repair
   abilities, please take it to a qualified mechanic. Something will stop
   your forward momentum, it may be your brakes or it may be one of
   numerous less desirable options.
   If anyone has any questions, or I may be of further service, please
   feel free to give me a call.
   (Editor's Note -- Larry Reynolds also operates Car Care Specialties
   Inc., Distributors of Quality Porsche Care Products, Post Office Box
   535, Saddle Brook, NJ 07663-0535. Phone 201-796-8300, Fax
   201-791-9743, E-mail