Possible Symptoms: Judder, Steering wheel Shaking, Grab release effect
The modern brake pad is designed to use cohesive friction to produce brake force. These brake pads transfer a thin layer of pad material on to the rotor surface known as the transfer layer. The braking force is achieved by continuously breaking the adhesive bonds between the brake pad and the transfer layer on the rotor.
A problem can occur if this transfer layer is not laid evenly and consistently on the rotor friction face. Inconsistencies in this transfer layer will cause uneven friction levels during braking. Over a reasonably short period of time these inconsistencies can progressively become more pronounced resulting in noticeable patchy blotches/rings on the rotor friction face.
The common initial symptoms can be vehicle surging during slow speed light braking, pedal pulsation, brake shudder and even steering wheel shake during high speed braking. This problem usually occurs as a result of the brake pads not being initially bedded in correctly so as to lay a consistent transfer layer evenly onto the face of the rotor. Slotted and/or drilled rotors can be more susceptible to this problem due to the pad cleaning effect of the slots and/or drilled holes.
If the problem is left unattended the symptoms will get progressively worse. This is due to the patches where the pad material deposits are building up with more deposits and where there are no deposits the rotor will increase in wear. This results in what is known as DTV (Disc Thickness Variation).
What can I do if my rotors already have Friction Material Deposits?
Rotors with Friction Material Deposits will require a light machine to restore the friction surface back to specification. Consideration then needs to be given to a more appropriate selection of brakes pads and ensuring that a suitable correct bed-in procedure is performed.
How do I select the correct pads for my driving style?
Do I tow? Do I drive like a race car driver? Do I own a performance car? Do I drive on the track? All of these questions need to be considered when choosing the correct brake pads. There is no one brand or compound that is right for every driver. It is a matter of discussing your needs with a good parts interpreter or your automotive technician to find the correct pad and possibly a little experimentation.
A basic guide to follow is:
1. If fitting a performance rotor (drilled or slotted) choose a slightly higher spec pad.
(E.g. Bendix Heavy Duty or equivalent or higher spec)
2. High Performance road pads are not suitable for constant track work – use a race pad.
3. Do not choose a high performance pad if you do not drive the car aggressively.
4. Using race pad compounds on the street will result in excessive pad and rotor wear.
Disc Brakes Australia