Can I expect dramatically improved braking from slotted or cross-drilled rotors?
DBA Street Series rotors will deliver better braking performance than conventional discs, but in most cases the improvement should be described as ‘significant’ or ‘worthwhile’ rather than ‘dramatic’.
There are several reasons why it is difficult to quantify exactly how much performance improvement DBA Street Series rotors can bring in typical road applications. It varies with the model of car, its kerb weight, the type of pads used (and how well they have been bedded in), the type of braking system into which the new rotors are being incorporated and the inherit effectiveness of the standard rotors being replaced.
Testing every type of vehicle under all conditions is clearly not possible. Nevertheless, we have tried a wide sample in varied situations. We have also interviewed as many owners as possible and are yet to talk to one who hasn’t been pleased with the improvement.
To get an additional expert view, Disc Brakes Australia commissioned respected advanced driving instructor (and three-time Australian NSW Hillclimb Champion) Peter Finlay to conduct a series of independent tests.
Finlay – the proprietor of Australian Nationwide Defensive Driving School – compared the stopping distances and general braking performance achieved with DBA Gold rotors and conventional ‘factory’ rotors under identical conditions.
During tests using Sydney’s Famous Oran Park Raceway as a closed and safe environment, a Holden/GM Commodore fitted with the DBA Gold cross-drilled and slotted product averaged a theoretical efficiency of 97 per cent over ten stops from 100 km/h. It recorded a best stop of 38.6 metres. The average stopping distance from 100 km/h was 40.4 metres. This compared with 42.6 metres (90.25 per cent theoretical efficiency) for the same car tested under similar conditions with standard rotors.
On both occasions, the car was fitted with similar brake pads, tyres and wheels. Finlay was the sole driver throughout and supervised the testing procedure to ensure a valid comparison.
The Finlay report noted that the DBA Gold rotors provided greater consistency from stop to stop and delivered good pedal feel. The ability to pull up the car 2.2 metres, or 5 per cent, is significant. Such a distance could easily be the difference between an accident and a near miss. However, it can’t be classified as a universal gain. Some cars may demonstrate less of an improvement with enhanced versions of DBA Street Series rotors while other cars, or perhaps other testing conditions, might reveal a bigger performance gain.
We feel, for example, that the DBA Street Series advantage would have increased even further if the speeds were higher and the cool-down period between stops was reduced (Finlay drove a 1 km cooldown loop between stops). On the other hand, the way the tests were conducted and the speed chosen – 100 km/h – is entirely relevant to everyday road requirements, as was the choice of Australia’s best selling car for the test.