News

Brake wear

Discussion in 'Ferrari Discussion (not model specific)' started by jdb, Dec 2, 2003.

  1. jdb

    jdb Formula Junior

    Nov 16, 2003
    273
    Northern California
    Full Name:
    Jeremy
    Hi, I bought a 355 in September and during the PPI got this:

    Brake pads measurements: front 10/32" rear 10/32"

    A couple weeks ago, my front brakes started to squeak. Does that mean they need replacement, or is 10/32" still a fair amount of pad left? I've put on maybe 400 miles of moderate driving since the brake pad measurements.
     
  2. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    6,333
    It is a sad fact of life that you can have A) brakes that don't squeek, or B) brakes that remove extremely large amounts of energy from a car in short order; time and time again. If you never used the brakes at more than 0./25 Gs of deceleration and never exceed the speed limit, you will (likely) never run into the brakes squeek issue. However, nobody I know drives a Ferrari like this.

    There are two kinds of squeeking, one can be managed by a sticky substance on the back sides of the pads, the other cannot. The one that can be solved with sticky stuff is a vibration induced between the calipers, the pads and the rotors. No matter how smooth the rotors look and feel, they are not perfectly smooth. The rough surface will induce vibrations into the pads, if there is a resonance, a squeek will occur.

    The other kind of squeek is caused by a chemical change in the material at the surface of a pad. The physics behind the issue is heat and what happens the the chemistry of brake pads and rotors under heat and pressure. Upon the application of the brakes at high speeds, a massive amount of heat is produced at the interface between the pad and rotor. The rotor may reach 1100 dF! This is hot enough to cause the pads and rotors to exchange atoms, and cause chemical changes in the rotor and in the surface of the pads. In effect, the surface of the pads becomes semi-molten and when it cools it cools in an amorphous state--that is it becomes a glass (a few microns thick). This amorphous surface is much more likely to cause vibration patterns that will resonate with the caliper and rotor, and thus causes brake squeeking. The heat also cooks the sticky stuff on the back of the pads and renders it useless.

    At a race track, the wear rate is sufficiently high that you wear through this amorphous region each time the brakes are used in earnest! So the end result is that if you take your car to the track (regularly!) you can ameliorate the brake squeeking issue (and loads of fun--using the car as intended). However, you will be replacing the pads with great regularity.
     
  3. jdb

    jdb Formula Junior

    Nov 16, 2003
    273
    Northern California
    Full Name:
    Jeremy
    Mitch,

    Thanks for the explanation! I'm having my calipers painted, and at that time will decide whether or not to replace my brake pads and/or rotors.

    Do cross-drilled rotors really make a difference? And do you have any advice on particular brake pads that are well-suited for fairly aggressive driving in a 355?
     

Share This Page