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Q:   What's the difference between slotted and drilled/slotted rotors? Which rotor will be best for my application?

A:  PSlots or grooves in rotor faces are partly a carryover from the days of asbestos pads. Asbestos and other organic pads were prone to “glazing” and the slots tended to help “scrape or de-glaze” them. Also, cross-drilling and/or slotting the rotor for racing purposes was beneficial by providing a way to expel the gasses created when the bonding agents employed to manufacture the pads began to break down at extreme temperatures. This condition is often referred to as “outgassing.” When it does occur, the driver still has a good firm brake pedal, but a significant reduction in friction. Normally this only happens at temperatures witnessed in racing. However, with today’s race pad technology, “outgassing” is no longer a concern with pads designed for racing.

So in the final analysis, drilling and slotting rotors has become popular in street applications for their pure aesthetic value. Wilwood provides rotors slotted, drilled or plain. For most performance applications, slotted is the preferred choice. With certain pad material, slotting can help wipe away debris from between the pad and rotor as well as increasing the coefficient of friction between the rotor and the pad. A drilled rotor provides the same type of benefit, but is more susceptible to cracking under severe usage; however, for street and occasional light duty track use, they will work fine. For more severe applications, we recommend slotted rotors.

Q:   Does my pad bedding process change at all if I have e-coated rotors?

A:  No, the bedding process is the same. Remember, proper break-in of pads and rotors is extremely important. Not doing so, can cause permanent damage to rotors and adversely affect overall brake performance. Pads and rotors interact with each other to provide efficient brake performance. The break-in or bed-in procedure is done to condition the pad/rotor interface. Depending on the pad used, more or less pad material is uniformly transferred onto the disc as a thin film. The resins and bonding agents in some pads need to be heat cycled to work properly as well. By not properly bedding-in pads, uneven pad material deposits can occur that may cause a vibration. Improper wear characteristics may also show up on either the pads, or rotors, or both. For further information on bedding, please consult Wilwood's Tech Tip Guide.You can also contact a Wilwood Sales Technician at 805-388-1188 or email Sales/Tech Support.

Q:   What do the black rotors look like once they are bedded-in?

A:  The annulus (where the pad comes in contact with the rotor) is quickly stripped of the e-coating and appears the same as any iron rotor. The e-coating remains in the radius around the drilled holes, and in the slots providing a nice contrast and high visibility of the drilled and slotting pattern of the rotor, as well as protecting those areas from rust.

Q:   Why are my rotors black, I wanted zinc?

A:  Wilwood uses a process called “E-Coating” to protect our rotors from corrosion. E-coating is another name for electrocoating, electropainting, or electrophoretic lacquering. It is used to deposit a protective coating as opposed to a metal such as is deposited by electroplating. Parts are dipped into a vat of the e-coat material and are electrified in order to promote a reaction at the surface, which deposits the protective agent. Through this process, we ensure that all exposed surfaces are protected from corrosion, providing the very best in protection. You can still order Zinc plated rotors as an option, but keep in mind that the zinc coating is more expensive and offers less rust protection than e-coat.

Wilwood Engineering, Inc
4700 Calle Bolero
Camarillo, CA 93012
Phone: (805) 388-1188
Fax: (805) 388-4938

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