KVR Performance Technical Release:

Cross drilled discs offer an enhanced initial bite (more responsive, especially in wet weather) and greater heat dissipation (reduction in heat induced fade - brake fade) over O.E.M.

Slotted discs offer cleaning of the friction material (Brake pads), but do little in terms of additional heat dissipation. Slotted brake discs do not cool better than cross drilled discs or even standard discs. The face groves will slice the brake pad allowing the pad to bite harder into the disc causing an increase in disc temperatures. This is recommended for competition vehicles to bring pad and disc temperatures up into optimal operating temperatures (race cars warm-up engines, tires and brakes for the best possible performance).

An additional technical note, proper slotting of a brake disc does not run off the outer diameter of the brake surface (this method can promote cracking as all brake discs expand with their release of thermal energy).

Recommending what to use can be challenging, the following should assist you to properly supply your readers:

What type of driver ?

REGULAR STREET - Use cross drilled and good brake fluid.

SPIRITED STREET - Use cross drilled, street sport brake pads, steel braided brake lines, and good brake fluid.

RACING STREET - Use cross drilled or slotted, street sport to mild competition brake pads, steel braided brake lines,good brake fluid, or possibly upgraded brake kit.

AMATEUR RACING - Use slotted, racing brake pads, steel braided brake lines, competition brake fluid, or possibly upgraded brake kit.

PROFESSIONAL RACING - Use upgraded brake kit or, when rules do not permit upgraded brake kits, use slotted, racing brake pads, steel braided brake lines, racing brake fluid.

These are general parameters, if specific information is required please contact our technical department.

Terry Gosse
Technical Director KVR Performance
www.kvrperformance.com

Why use drilled or slotted discs?
Drilling or slotting discs aids the disc in several ways:
The edges of the slots or holes continuously clean and refresh the pad surface as well as providing increased brake "bite". Additionally, they prevent gasses from collecting between the pad and disc interface.
The disc is lightened, thereby decreasing its rotational inertia.
Improved ventilation increases the disc'* ability to shed heat, resulting in cooler operating temperatures

What are the advantages of drilled and slotted discs?
The main advantages of drilled and slotted discs are the same: increased brake "bite", and a continuous refreshing of the brake pad surface. Drilled discs have the additional advantage of being lighter and running cooler. However, there are certain pad materials that should not be used with a drilled disc.

Why are there so many holes in a cross-drilled disc?
The number of holes in a cross-drilled disc is part of the engineered system. Brembo has done extensive testing with regards to the number of holes, their size, their location and their chamfering. This attention to detail is what truly sets Brembo apart in the world of braking. The same attention to detail that is delivered to the Ferrari Formula One effort is a component of the high performance program. The number of holes in a disc is in part a function of the size of the disc and the internal venting (if it is a vented disc).

Are discs with cast-in-place holes better than cross-drilled discs?
Brembo has extensively studied and tested cross-drilling versus casting the holes in place and found no significant effect on performance or durability.

What are the benefits to Crossdrilling, Slotting, and Zinc-Washing my rotors?
In years past, crossdrilling 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 “green pad fade” or “outgassing”. When it does occur, the driver still has a good firm brake pedal, but simply little or no friction. Since this normally happens only at temperatures witnessed in racing, this can be very exciting!

However, with today’* race pad technology, ‘outgassing’ is no longer much of a concern. When shopping for races pads, or even ultra-high performance road pads, look for the phrases, “dynamic surface treatment”, “race ready”, and/or, “pre-burnished”. When these or similar statements are made by the pad manufacturer, the pad in question will likely have little or no problem with ‘outgassing’. Ironically more pedestrian pads used on most streetcars will still exhibit ‘outgassing’, but only when used at temperatures normally only encountered on the racetrack.

Although crossdrilling and/or slotting will provide a welcome path to expend any gasses when and if they develop, it is primarily a visual enhancement behind today’* often wide-open wheel designs.

Crossdrilling offers the greatest gas relief pathway, but creates potential “stress risers” from which cracks can occur. Baer’* rotors are cast with crossdrilling in mind, from the material specified, to curved vanes, behind which the holes are placed to minimize potential crack migration. Slotted surfaces are what Baer recommends for track only use. Slotted only rotors are offered as an option for any of Baer’* offerings.

Zinc washing is then done to provide a barrier, which resists development of surface scales or rust.

Q: I don’t want to spend the money for a complete brake upgrade. Do you offer cross drilled rotors to work with my factory brakes?

Yes. Although there are some companies which sell cross-drilled rotors as an actual performance upgrade, in our extensive testing we have seen no improvement to be had by simply crossdrilling stock rotors. This is why Baer has developed EradiSpeed™ rotor upgrades for a variety of applications. Although it is true the crossdrilling, the slotting, or for that matter the zinc surface washing, are cosmetic enhancements, EradiSpeed™ rotor packages also feature rotors with thicker cheeks to provide more heat sink capacity in the fire path of the rotor. Also, they all feature directional vanes for greater pumping efficiency, as well as a two-piece design where the hat, or hub/hat section of the rotor is CNC machined from a solid billet of aluminum and is then fixed to the rotor ring using National Aviation Standard (NAS) stainless hardware. In other words, the EradiSpeed™ is much more than just the most visually appealing direct replacement rotor, it is the only upgrade of its type which can actually deliver the benefits of greater heat absorption, increased durability and lighter total weight.

In racing, crossdrilling was designed to alleviate a problem known as out-gassing. In some of the older pad compounds, when the pads reached elevated temperatures consistent with performance or racing use, the binder (that’* the material that holds the friction material in place) boiled off, producing a gas. This gas would build up between the rotor and the brake pad, effectively keeping the pad from directly contacting the rotor. The holes provide a relief path for these gasses, as do slots, so the pad can once again contact the rotor. Crossdrilling was NOT designed to facilitate cooling.

Although Baer offers crossdrilling as an option on their systems, it is offered as a cosmetic option only. However, with an EradiSpeed™ rotor upgrade, unlike a cosmetically altered stock replacement rotor, you will benefit from improved durability, greater heat sink capacity, lighter total weight and the visual excitement of a 2-piece, aluminum centered, crossdrilled, slotted and zinc washed appearance.

Disc Cooling
A good source of cooling air should be supplied preferably through the upright to the disc throat. A typical venting cross section of 100cm² (16in²) is usually sufficient. The pick up should preferably be in an area of clean high pressure air flow and the ducting should be arranged to avoid sharp bends or changes in section which may choke the air flow.

Careful design of the Mounting Bell is important in achieving effective disc cooling and avoiding problems. Typically 80% of the airflow should be directed up the disc vents and 10% up each face of the disc. This ratio can vary considerably in practice but it is important that both disc faces are cooled equally by adjusting the air gaps. Unequal face temperatures can lead to disc distortion and a long pedal. Lightening holes in the bells should be avoided as available cooling air can be lost without cooling the disc.


Safety & Care of Discs
Cast iron brake discs should not normally be operated at bulk temperatures in excess of 6l0°C and above rotational speeds of 3000 revolutions per minute.

Discs must be regularly and frequently inspected for excessive heat crazing and cracking.

Discs with cracks emanating from mounting holes / slots, inside diameter, scallops, or outside diameter should be changed immediately.

After heavy and prolonged use some surface crazing will often be evident. If this turns into distinct surface cracks which are radiating towards the inside or outside diameter the disc should be changed.

Z51 Performance Package. The Z51 Performance Package brings Corvette Coupe performance very close to the same level as the widely admired Z06. The Z51 offers more aggressive dampers and springs, larger stabilizer bars, and larger, cross-drilled brake rotors for optimum track performance capability while still providing a well-controlled and comfortable ride. Extensive racetrack testing reveals that a C6 equipped with the Z51 suspension almost equals the lap time of a C5 Z06 – marking a major advance in the overall performance of a Corvette Coupe by nearly approximating the extreme performance capabilities of the vaunted Z06 at a remarkable value.

Generally true race cars use either a combination of drilled and slotted or just slotted. This is due to the fact that their fade characteristics will lessen at higher temperatures. Let’* look at a 100% road race car for example.

These cars will use a slotted (and drilled at times) rotor exclusively due to the high demand that they put on the brake systems. These rotors will provide better braking at higher levels usually seen at an open track (circular) event or even endurance race. While these rotors work well under these conditions, they may not be suitable for lower temperature and low demand road race tracks.. They can hinder the braking capabilities due to the fact that they will need higher temps to work efficiently.