ARE THERE ANY TRADE-OFFS WITH USING SLOTTED OR CROSS-DRILLED ROTORS?

When a car-manufacturer designs a disc rotor, the aim is to please the ‘average’ owner, placing high priority on such things as quietness, durability and low production costs.

When enthusiasts change their cars to improve performance they always have to accept some tradeoffs. After all, there’s no such thing as something for nothing. In this case, the main trade-off for improved braking is higher purchase price. The extra cost is due to there being a great deal more production work in manufacturing rotors that are slotted, or crossdrilled and slotted. The specialist nature of the product also adds to the expense, reducing production
economies of scale.

However, we’ve done our best to keep the price premiums as small as possible, using innovative lowvolume manufacturing techniques. Many customers feel the additional cost of the DBA Slotted or DBA

Gold rotors is justified by the enhanced performance alone, and consider that the attractive appearance is merely a bonus. In an emergency situation, every buyer will appreciate the extra stopping power even if they rarely drive hard enough to utilise it.

As any driver knows, the ability to pull up a car even one metre sooner can save a life. Something to note about slotting: as the rotor wears, the slotting becomes shallower and therefore less effective. The DBA Street Series slots are tailored to each rotor type, but typically they are about 1.5mm deep x 3mm wide. By the time the rotor has reached ‘minimum thickness’ (we are careful to point out that the slots are not intended as a wear indicator), there is not much slot left. To make them deeper would risk weakening the rotor.

In contrast, the holes remain effective in combating ‘out-gassing’ for the whole life of the disc. As with slots, the pattern is unique for each rotor type, typically we have between 24 and 36 holes per disc face, each with a diameter of 5mm. To counter the tendency for cracks to form between holes, we previously put just one hole per vane on ventilated discs to ensure the walls between the vanes would act as a strengthening barrier between the holes. The increasing adoption of the patented Kangaroo Paw ventilation system on DBA Street Series rotors, however, has made this more complex.

The Kangaroo Paw system doesn’t use traditional vanes - it uses a series of diamond shaped pillars to promote greater airflow. The holes now need to be positioned next to these pillars. In a manufacturing sense this is more complex, but from a buyer’s point of view it gives a disc that is stronger as well as better cooled. Each hole is chamfered or ‘radiused’ around its opening to reduce pad abrasion and provide a smooth transition between hole and friction area.

Under some circumstances a small clicking noise may occur as a result of the pads running across the holes.