IS A CROSS-DRILLED AND SLOTTED DISC BRAKE ROTOR
WEAKER?

Removing any metal from a rotor can potentially weaken it but working in the DBA Gold’s favour is Disc Brakes Australia’s policy of safe, conservative designs (our discs are even over-engineered, some suggest), and the basic strength of the case iron alloy used.

At DBA, we spent two years getting all aspects right before launching the product to the public. This research and development included perfecting the symmetrical hole pattern which ensures that the discs have correct balance, optimum cooling properties and sufficient contact area with the pads.

We’ve also put a lot of time into programming our computer-controlled (CNC) milling machines to carefully shape the edges of the holes to avoid tearing up brake pads. And we are using manufacturing equipment accurate to within three one-millionths of a metre. Some potential buyers have expressed concern about the likelihood of cracking.

This is reasonable, as even standard factory rotors can suffer cracking under extreme use or abuse. Proper bedding of
both rotors and pads minimises this risk.

The weakest or most crack-prone part of the rotor is the outer edge, which is the normal course of expanding and contracting with heat, endures more movement then the centre of the disc, which is obviously smaller and is reinforced by the central hub or hat.This is why DBA Street Series road discs do not follow the practice of some racing rotors, which have holes right at the outer edge or run slots off the edge of the disc.

Reports from a few owners confirm the very occasional appearance of very small cracks around the holes. These are caused by localised stresses and in no way detract from the reliability, durability or ‘stop-ability' of the disc. And a recent change on some discs from a chamfered hole profile (one with a 45-degree bevelled edge) to a ‘radiused' one (with a continuous curve between the friction surface and the opening) has further reduced these incidences.

Some rotors have been returned with more serious structural cracking, however the number equates to less than 0.2 per cent of rotors shipped. And of these, most were used in motor sport applications, something they were not designed or warranted for. To be frank, most of these owners would have destroyed non-drilled rotors under the same conditions. They were simply asking too much of their standard braking system and should have upgraded to our purpose-built motor sport rotors and possibly bigger calipers as well.