DBA Steve
11-10-2009, 03:46 PM
From the DBA FAQ at www.dba.com.au
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Disc Brakes Australia (DBA) frankly answers questions about the company’s popular range of slotted and cross-drilled Street Series rotors.
http://www.racedotcom.com/attachment.php?attachmentid=76&stc=1&d=1255240189
WHAT ARE DBA STREET SERIES ENHANCED
PERFORMANCE ROTORS?
DBA Street Series is the name given to Disc Brakes Australia’s entry level range of direct replacement rotors. This range includes standard rotors to fit almost every make and model on the road, plus enhanced performance variants that incorporate cross-drilling and slotting yet are still aimed at the price conscious end of the market.
All the enhanced performance rotors are manufactured in Australia by Disc Brakes Australia and are designed to give greater stopping power and improved appearance. Equally importantly, these rotors can be easily fitted to road cars in place of conventional discs. They bring to the affordable end of the 'street' market the sort of braking technology normally associated with expensive high-performance machines.
DBA also manufactures and sells two high-end rotor ranges (the 4000 Series and 5000 Series) aimed at those involved in motor sport and other extreme driving applications.
CAN I USE THESE ROTORS FOR MOTOR SPORT?
No. The range of DBA Street Series rotors are designed (and warranted) for street use only. With the enhanced performance versions of the DBA Street Series product, we’ve carefully found a balance between extra performance and the safety, durability and affordability required by everyday street users. The sort of motor sport which road cars tend to be involved with (club lap dashes and sprint races) is particularly hard on rotors, usually involving a set of cold brakes into the first corner and, at the end, a car parked with the rotors still at 500 degrees Celsius. In such circumstances it is easy to warp discs, or even to weld the pads onto the disc surface. DBA’s premium rotors (the 4000 Series
and 5000 Series) incorporate Thermal Stability Profiling and other technology to enhance their ability to handle such extreme treatment.
WHAT DOES ‘CROSS-DRILLED AND SLOTTED’ MEAN?
The expression 'cross drilled and slotted' refers to two separate processes, and the enhanced performance versions of DBA Street Series rotors incorporate one (DBA Slotted) or both (DBA Gold).
The first procedure involves drilling holes through the friction surfaces of the rotor and the second refers to milling a series of grooves from the centre of the disc toward the edge. The processes are aimed at making the disc better ventilated and more effective. And let’s not forget the cosmetic side: DBA Street Series rotors look aggressive and purposeful, particularly with today’s open-patterned alloy wheels.
DOES A DISC NEED TO BE CROSS-DRILLED AND SLOTTED?
Not necessarily. The processes achieve slightly different ends.
Let’s talk about cross-drilling first. When the friction surfaces of a rotor are smooth and flat, there is no means of escape for the gases and dust that build up between pad and rotor. At very high braking temperatures, the bonding agents used in some brake pads can produce a gas which creates a pneumatic cushion between pad and rotor, giving a driver a normal pedal feel but reducing the amount of friction being generated. This is not a huge problem in normal motoring but is an important consideration in street performance applications.
The bigger the pads and the higher the braking temperatures, the more likely the problem. The drill holes assist with this 'out gassing'. The holes are also commonly labelled 'cooling holes' because of the improvements they make in this area. Better cooling means less fade during repeated heavy brake applications.
Obviously, the holes reduce mass. They also help dissipate water when driving in poor weather.
WHAT DOES SLOTTING DO?
Slotting increases the bite of the pads. This helps pull the car up more quickly. Used on its own, the process doesn’t involve removing as much metal as cross-drilling, so it doesn’t result in as great a weight saving. However, slotting can be as effective as cross-drilling in combating the problem of 'outgassing', particularly with the nine uni-directional slots fitted to each side of DBA Slotted rotors. The slots pump away gas and restore full contact.
The 'micro-shaving' effect of the slots also serves to de-glaze the pads (this is why the edges of the slots on DBA Street Series rotors are not chamfered or 'radiused'). It also tends to even out the wear across the brake pad faces, increasing the effective contact area. This can extend rotor life.
HOW DO THE TWO APPROACHES COMPARE IN PERFORMANCE?
Research has shown the overall stopping power provided by the DBA Slotted and DBA Gold rotors is remarkably similar. Because of their lighter weight and increased cooling, the DBA Gold rotors recover more quickly and have the edge in situations where there is hard braking in short bursts.
The major advantage of the DBA Slotted is an ability to absorb and dissipate heat more evenly and to sustain higher temperatures for longer. That makes them particularly good for continuous heaving braking situation, such as experienced when driving down a mountain or when towing.
DO THE SLOTS NEED TO BE LEFT-HANDED AND RIGHTHANDED TO WORK PROPERLY?
Conventional wisdom once said so ñ and also dictated that all slots to be swept back from the centre in the same direction. However, with computer modelling we’ve managed to make the slots on the DBA Gold rotors work in combination with the cross-drilling. This enables us to use four grooves arranged in a mirror-image pattern, creating a disc that works equally effectively in either direction (which is to say, on either side of the car). To provide maximum efficiency with slotting only, the DBA Slotted rotors have non-interchangeable left-handed and right-handed patterns.
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.
Move on to part 2 (http://www.racedotcom.com/showthread.php?p=30958#post30958) for more of the definitive guide to everything you wanted to know and you might liketo also look at the video series at http://www.youtube.com/watch?v=wdvUxqKj-Zc&feature=channel
DBA Steve
www.dba.com.au
-------------------------------------------------------------
Disc Brakes Australia (DBA) frankly answers questions about the company’s popular range of slotted and cross-drilled Street Series rotors.
http://www.racedotcom.com/attachment.php?attachmentid=76&stc=1&d=1255240189
WHAT ARE DBA STREET SERIES ENHANCED
PERFORMANCE ROTORS?
DBA Street Series is the name given to Disc Brakes Australia’s entry level range of direct replacement rotors. This range includes standard rotors to fit almost every make and model on the road, plus enhanced performance variants that incorporate cross-drilling and slotting yet are still aimed at the price conscious end of the market.
All the enhanced performance rotors are manufactured in Australia by Disc Brakes Australia and are designed to give greater stopping power and improved appearance. Equally importantly, these rotors can be easily fitted to road cars in place of conventional discs. They bring to the affordable end of the 'street' market the sort of braking technology normally associated with expensive high-performance machines.
DBA also manufactures and sells two high-end rotor ranges (the 4000 Series and 5000 Series) aimed at those involved in motor sport and other extreme driving applications.
CAN I USE THESE ROTORS FOR MOTOR SPORT?
No. The range of DBA Street Series rotors are designed (and warranted) for street use only. With the enhanced performance versions of the DBA Street Series product, we’ve carefully found a balance between extra performance and the safety, durability and affordability required by everyday street users. The sort of motor sport which road cars tend to be involved with (club lap dashes and sprint races) is particularly hard on rotors, usually involving a set of cold brakes into the first corner and, at the end, a car parked with the rotors still at 500 degrees Celsius. In such circumstances it is easy to warp discs, or even to weld the pads onto the disc surface. DBA’s premium rotors (the 4000 Series
and 5000 Series) incorporate Thermal Stability Profiling and other technology to enhance their ability to handle such extreme treatment.
WHAT DOES ‘CROSS-DRILLED AND SLOTTED’ MEAN?
The expression 'cross drilled and slotted' refers to two separate processes, and the enhanced performance versions of DBA Street Series rotors incorporate one (DBA Slotted) or both (DBA Gold).
The first procedure involves drilling holes through the friction surfaces of the rotor and the second refers to milling a series of grooves from the centre of the disc toward the edge. The processes are aimed at making the disc better ventilated and more effective. And let’s not forget the cosmetic side: DBA Street Series rotors look aggressive and purposeful, particularly with today’s open-patterned alloy wheels.
DOES A DISC NEED TO BE CROSS-DRILLED AND SLOTTED?
Not necessarily. The processes achieve slightly different ends.
Let’s talk about cross-drilling first. When the friction surfaces of a rotor are smooth and flat, there is no means of escape for the gases and dust that build up between pad and rotor. At very high braking temperatures, the bonding agents used in some brake pads can produce a gas which creates a pneumatic cushion between pad and rotor, giving a driver a normal pedal feel but reducing the amount of friction being generated. This is not a huge problem in normal motoring but is an important consideration in street performance applications.
The bigger the pads and the higher the braking temperatures, the more likely the problem. The drill holes assist with this 'out gassing'. The holes are also commonly labelled 'cooling holes' because of the improvements they make in this area. Better cooling means less fade during repeated heavy brake applications.
Obviously, the holes reduce mass. They also help dissipate water when driving in poor weather.
WHAT DOES SLOTTING DO?
Slotting increases the bite of the pads. This helps pull the car up more quickly. Used on its own, the process doesn’t involve removing as much metal as cross-drilling, so it doesn’t result in as great a weight saving. However, slotting can be as effective as cross-drilling in combating the problem of 'outgassing', particularly with the nine uni-directional slots fitted to each side of DBA Slotted rotors. The slots pump away gas and restore full contact.
The 'micro-shaving' effect of the slots also serves to de-glaze the pads (this is why the edges of the slots on DBA Street Series rotors are not chamfered or 'radiused'). It also tends to even out the wear across the brake pad faces, increasing the effective contact area. This can extend rotor life.
HOW DO THE TWO APPROACHES COMPARE IN PERFORMANCE?
Research has shown the overall stopping power provided by the DBA Slotted and DBA Gold rotors is remarkably similar. Because of their lighter weight and increased cooling, the DBA Gold rotors recover more quickly and have the edge in situations where there is hard braking in short bursts.
The major advantage of the DBA Slotted is an ability to absorb and dissipate heat more evenly and to sustain higher temperatures for longer. That makes them particularly good for continuous heaving braking situation, such as experienced when driving down a mountain or when towing.
DO THE SLOTS NEED TO BE LEFT-HANDED AND RIGHTHANDED TO WORK PROPERLY?
Conventional wisdom once said so ñ and also dictated that all slots to be swept back from the centre in the same direction. However, with computer modelling we’ve managed to make the slots on the DBA Gold rotors work in combination with the cross-drilling. This enables us to use four grooves arranged in a mirror-image pattern, creating a disc that works equally effectively in either direction (which is to say, on either side of the car). To provide maximum efficiency with slotting only, the DBA Slotted rotors have non-interchangeable left-handed and right-handed patterns.
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.
Move on to part 2 (http://www.racedotcom.com/showthread.php?p=30958#post30958) for more of the definitive guide to everything you wanted to know and you might liketo also look at the video series at http://www.youtube.com/watch?v=wdvUxqKj-Zc&feature=channel
DBA Steve
www.dba.com.au