The majority of brake squealing is caused by harmonics occurring at the metal-to-metal contact points on the brake calipers. Examples include:
- Where the caliper pistons contact with the back of the brake pad
- Where retaining pins and spring clips contact each other, or the caliper
- The slide on a floating caliper
- Where the caliper bolts onto the spindle
The fix is generally to disassemble the caliper (but leaving the pistons intact); clean the metal-to-metal contact points to remove any rust; apply a thin film of high temperature anti-seize at all metal-to-metal contact points; and reassemble.
In rare cases, the surface of the rotor and/or the pads have become glazed, and switching pads & sanding the rotor face will help.....but again this is not common. Sometimes, changing to a different brake pad compound will also help, by moving the vibration frequency out of the harmonic zone.
Often, the biggest challenge to fixing squealing brakes is finding a mechanic that understands these fine points, and is willing to take the time to do the work properly. If your dealership can't seem to correct the problem, start looking around for a good independent Porsche shop.
Like that other thread said recently....It pays to have a "friend" in the business.
