Solid vs Cross drilled vs Slotted
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Solid vs Cross drilled vs Slotted
More and more hi-end/hi-performance cars in the market come with either cross-drilled, slotted or cross-drilled and slotted brake rotors. Mercedes, Porche, Corvette, BMW, Ferrari, just to name a few.
There are always debates about pro/con of the products. Since JCW come with the cross-drilled / slotted rotor as their JCW brake accessory. Will it works, will it really that bad or is it just for the look.
Let's the debate begin.
Below is from Corvette forum, to start with.
Happy motoring. 
There are always debates about pro/con of the products. Since JCW come with the cross-drilled / slotted rotor as their JCW brake accessory. Will it works, will it really that bad or is it just for the look.
Let's the debate begin.
Below is from Corvette forum, to start with.
Originally Posted by Corvette Forum
Cracking Cracking is primarily due to heat cycling that weakens the cast iron discs. The exact mechanism of this failure is disputed. Cast iron discs are formed with the excess carbon being precipitated in the form of carbon plates or flakes dispersed throughout the ferrite (iron) matrix. What is believed to happen is that when discs are operated above about 900º F, the carbon becomes more flexible or "fluid" in its shape partly due to the thermal expansion of the enclosing ferrite matrix. Then, as the disc cools relatively rapidly back below about 900º F the carbon is trapped in a changed more random shape then when it was first cast. This creates internal stress on the part and continuously transforms the disc by relieving the stress through the cracking. The cracks begin by appearing between carbon flakes. Nodular or ductile iron would resist this cracking due to the excess carbon being precipitated in a spheroidal form, but it, like other alternative materials do not have the mechanical properties needed to function ideally in a brake disc application. In discs that are cast to resist cracking through chemistry and controlled cooling at the foundry, cracking will still occur, but more slowly and take the form of heat checks on the surface. In some cases cracks will begin at the periphery of the disc and propagate inwards. In this situation, propagation can be delayed by drilling small holes at the end of the cracks (stop drilling). We do not recommend this however, because if the cracks continue to propagate unnoticed, catastrophic mechanical failure will result. Replace disc at the first sign of cracks at the outer edge of any size. A historic note, the original purpose of the curved or angled vane disc was to prevent cracks from propagating by imposing a solid vane in the path of the crack. The cooling function was secondary.
Cryogenic treatment : A thermal process in which metallic components are slowly cooled to near Kelvin temperature and then equally slowly returned to room temperature. Proponents claim that the grain structure is refined by the process. There is considerable doubt about the effectiveness of the process. Evidence is largely anecdotal and to date no scientific and quantitated engineering studies have been published.
Drilled or cross-drilled rotors
Discs that have been drilled through with a non-intersecting pattern of radial holes. The objects are to provide a number of paths to get rid of the boundary layer of out gassed volatiles and incandescent particles of friction material and to increase "bite" through the provision of many leading edges. The advent of carbon metallic friction materials with their increased temperatures and thermal shock characteristics ended the day of the drilled disc in professional racing. They are still seen (mainly as cosmetic items) on motorbikes and some road going sports cars. Typically in original equipment road car applications these holes are cast then finished machined to provide the best possible conditions by which to resist cracking in use. But they will crack eventually under the circumstances described in another section (see Cracking). Properly designed, drilled discs tend to operate cooler than non-drilled ventilated discs of the same design due the higher flow rates through the vents from the supplemental inlets and increased surface area in the hole. That's right, inlets. The flow is into the hole and out through the vent to the OD of the disc. If discs are to be drilled, the external edges of the holes must be chamfered (or, better yet, radiused) and should also be peened.
Darrick Dong; Director of Motorsports at Performance Friction: "Anyone that tells you that drilling makes the disc run cooler is smoking crack."
Power Slot: "At one time the conventional wisdom in racing circles was to cross-drill brake rotors to aid cooling and eliminate the gas emitted by brake pads. However, today’s elite teams in open wheel, Indy and Trans Am racing are moving away from crack prone, cross-drilled brake rotors in favor of rotors modified with a fatigue resistant slotting process."
Stop Tech: "StopTech provides rotors slotted, drilled or plain. For most performance applications slotted is the preferred choice. Slotting helps wipe away debris from between the pad and rotor as well as increasing the "bite" characteristics of the pad. A drilled rotor provides the same type of benefit, but is more susceptible to cracking under severe usage. Many customers prefer the look of a drilled rotor and for street and occasional light duty track use they will work fine. For more severe applications, we recommend slotted rotors." (Note that even though Stop Tech sells both drilled and slotted rotors they do not recommend drilled rotors for severe applications.)
Wilwood: "Q: Why are some rotors drilled or slotted?
A: Rotors are drilled to reduce rotating weight, an issue near and dear to racers searching for ways to minimize unsprung weight. Drilling diminishes a rotor's durability and cooling capacity."
From Waren Gilliand: (Warren Gilliland is a well-known brake engineer in the racing industry and has more than 32 years experience in custom designing brake systems ...he became the main source for improving the brake systems on a variety of different race vehicles from midgets to Nascar Winston Cup cars.) "If you cross drill one of these vented rotors, you are creating a stress riser that will encourage the rotor to crack right through the hole. Many of the rotors available in the aftermarket are nothing more than inexpensive offshore manufactured stock replacement rotors, cross drilled to appeal to the performance market. They are not performance rotors and will have a corresponding high failure rate"
From Baer: "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...However, with today’s race pad technology, ‘outgassing’ is no longer much of a concern...Slotted surfaces are what Baer recommends for track only use. Slotted only rotors are offered as an option for any of Baer’s offerings."
Grassroots Motorsports: "Crossdrilling your rotors might look neat, but what is it really doing for you? Well, unless your car is using brake pads from the '40s and 50s, not a whole lot. Rotors were first drilled because early brake pad materials gave off gasses when heated to racing temperatures, a process known as "gassing out." ...It was an effective solution, but today's friction materials do not exhibit the some gassing out phenomenon as the early pads. Contrary to popular belief, they don't lower temperatures. (In fact, by removing weight from the rotor, they can actually cause temperatures to increase a little.) These holes create stress risers that allow the rotor to crack sooner, and make a mess of brake pads--sort of like a cheese grater rubbing against them at every stop. Want more evidence? Look at NASCAR or F1. You would think that if drilling holes in the rotor was the hot ticket, these teams would be doing it...Slotting rotors, on the other hand, might be a consideration if your sanctioning body allows for it. Cutting thin slots across the face of the rotor can actually help to clean the face of the brake pads over time, helping to reduce the glazing often found during high-speed use which can lower the coefficient of friction. While there may still be a small concern over creating stress risers in the face of the rotor, if the slots are shallow and cut properly, the trade-off appears to be worth the risk. (Have you looked at a NASCAR rotor lately?)
AP Racing: "Grooves improve 'cleaning' of the pad surfaces and result in a more consistent brake performance. Grooved discs have a longer life than cross-drilled discs."
also from AP: "Cross drilled...can compromise disc life. Radiused drilled...mainly used for aesthetic reasons on road applications."
Cryogenic treatment : A thermal process in which metallic components are slowly cooled to near Kelvin temperature and then equally slowly returned to room temperature. Proponents claim that the grain structure is refined by the process. There is considerable doubt about the effectiveness of the process. Evidence is largely anecdotal and to date no scientific and quantitated engineering studies have been published.
Drilled or cross-drilled rotors
Discs that have been drilled through with a non-intersecting pattern of radial holes. The objects are to provide a number of paths to get rid of the boundary layer of out gassed volatiles and incandescent particles of friction material and to increase "bite" through the provision of many leading edges. The advent of carbon metallic friction materials with their increased temperatures and thermal shock characteristics ended the day of the drilled disc in professional racing. They are still seen (mainly as cosmetic items) on motorbikes and some road going sports cars. Typically in original equipment road car applications these holes are cast then finished machined to provide the best possible conditions by which to resist cracking in use. But they will crack eventually under the circumstances described in another section (see Cracking). Properly designed, drilled discs tend to operate cooler than non-drilled ventilated discs of the same design due the higher flow rates through the vents from the supplemental inlets and increased surface area in the hole. That's right, inlets. The flow is into the hole and out through the vent to the OD of the disc. If discs are to be drilled, the external edges of the holes must be chamfered (or, better yet, radiused) and should also be peened.
Darrick Dong; Director of Motorsports at Performance Friction: "Anyone that tells you that drilling makes the disc run cooler is smoking crack."
Power Slot: "At one time the conventional wisdom in racing circles was to cross-drill brake rotors to aid cooling and eliminate the gas emitted by brake pads. However, today’s elite teams in open wheel, Indy and Trans Am racing are moving away from crack prone, cross-drilled brake rotors in favor of rotors modified with a fatigue resistant slotting process."
Stop Tech: "StopTech provides rotors slotted, drilled or plain. For most performance applications slotted is the preferred choice. Slotting helps wipe away debris from between the pad and rotor as well as increasing the "bite" characteristics of the pad. A drilled rotor provides the same type of benefit, but is more susceptible to cracking under severe usage. Many customers prefer the look of a drilled rotor and for street and occasional light duty track use they will work fine. For more severe applications, we recommend slotted rotors." (Note that even though Stop Tech sells both drilled and slotted rotors they do not recommend drilled rotors for severe applications.)
Wilwood: "Q: Why are some rotors drilled or slotted?
A: Rotors are drilled to reduce rotating weight, an issue near and dear to racers searching for ways to minimize unsprung weight. Drilling diminishes a rotor's durability and cooling capacity."
From Waren Gilliand: (Warren Gilliland is a well-known brake engineer in the racing industry and has more than 32 years experience in custom designing brake systems ...he became the main source for improving the brake systems on a variety of different race vehicles from midgets to Nascar Winston Cup cars.) "If you cross drill one of these vented rotors, you are creating a stress riser that will encourage the rotor to crack right through the hole. Many of the rotors available in the aftermarket are nothing more than inexpensive offshore manufactured stock replacement rotors, cross drilled to appeal to the performance market. They are not performance rotors and will have a corresponding high failure rate"
From Baer: "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...However, with today’s race pad technology, ‘outgassing’ is no longer much of a concern...Slotted surfaces are what Baer recommends for track only use. Slotted only rotors are offered as an option for any of Baer’s offerings."
Grassroots Motorsports: "Crossdrilling your rotors might look neat, but what is it really doing for you? Well, unless your car is using brake pads from the '40s and 50s, not a whole lot. Rotors were first drilled because early brake pad materials gave off gasses when heated to racing temperatures, a process known as "gassing out." ...It was an effective solution, but today's friction materials do not exhibit the some gassing out phenomenon as the early pads. Contrary to popular belief, they don't lower temperatures. (In fact, by removing weight from the rotor, they can actually cause temperatures to increase a little.) These holes create stress risers that allow the rotor to crack sooner, and make a mess of brake pads--sort of like a cheese grater rubbing against them at every stop. Want more evidence? Look at NASCAR or F1. You would think that if drilling holes in the rotor was the hot ticket, these teams would be doing it...Slotting rotors, on the other hand, might be a consideration if your sanctioning body allows for it. Cutting thin slots across the face of the rotor can actually help to clean the face of the brake pads over time, helping to reduce the glazing often found during high-speed use which can lower the coefficient of friction. While there may still be a small concern over creating stress risers in the face of the rotor, if the slots are shallow and cut properly, the trade-off appears to be worth the risk. (Have you looked at a NASCAR rotor lately?)
AP Racing: "Grooves improve 'cleaning' of the pad surfaces and result in a more consistent brake performance. Grooved discs have a longer life than cross-drilled discs."
also from AP: "Cross drilled...can compromise disc life. Radiused drilled...mainly used for aesthetic reasons on road applications."
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6th Gear
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From: Ellicott City, MD
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6th Gear
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From: Ellicott City, MD
Any secret behind all of this?
Why do many of the exotic cars and super cars have used and still using drilled or slotted rotors?
Is it really just for show?
Since it's been proved that the solid rotor performs better, why are they still using them? Interesting, isn't it.
Umm.....
Why do many of the exotic cars and super cars have used and still using drilled or slotted rotors?
Is it really just for show?
Since it's been proved that the solid rotor performs better, why are they still using them? Interesting, isn't it.
Umm.....
OVERDRIVE - Racing Champion
Joined: Feb 2003
Posts: 15,262
Likes: 72
From: Mililani, Hawaii
Any secret behind all of this?
Why do many of the exotic cars and super cars have used and still using drilled or slotted rotors?
Is it really just for show?
Since it's been proved that the solid rotor performs better, why are they still using them? Interesting, isn't it.
Umm.....
Why do many of the exotic cars and super cars have used and still using drilled or slotted rotors?
Is it really just for show?
Since it's been proved that the solid rotor performs better, why are they still using them? Interesting, isn't it.
Umm.....
Since one exotic is doing it the others want to look nice too.
If brakes were not as easily seen would they still do it? Probably not.
If you have a show car then it makes sense to dress up the brakes that way.
I had zimmerman cross drilled rotors and it took less than one year to form minute cracks in both front rotors with mostly street use, not that many miles and some track and driving school, nothing excessive and I am not that hard on my brakes. Rear drilled rotors did fine.
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6th Gear
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From: Ellicott City, MD
It's bling and market demand for looks.
Since one exotic is doing it the others want to look nice too.
If brakes were not as easily seen would they still do it? Probably not.
If you have a show car then it makes sense to dress up the brakes that way.
I had zimmerman cross drilled rotors and it took less than one year to form minute cracks in both front rotors with mostly street use, not that many miles and some track and driving school, nothing excessive and I am not that hard on my brakes. Rear drilled rotors did fine.
Since one exotic is doing it the others want to look nice too.
If brakes were not as easily seen would they still do it? Probably not.
If you have a show car then it makes sense to dress up the brakes that way.
I had zimmerman cross drilled rotors and it took less than one year to form minute cracks in both front rotors with mostly street use, not that many miles and some track and driving school, nothing excessive and I am not that hard on my brakes. Rear drilled rotors did fine.
I've heard that Porsche's drilled rotors' been cast with pre-drilled hole on it. And some of them using different material, such as carbon-ceramic drilled rotor on Ferrari F430.
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The $$$$ PCCB brake rotors, a Porsche technology.
Porsche Ceramic Composite Brakes (PCCB) use a cross-drilled, carbon fiber reinforced ceramic disc with special composite pads. During manufacture, the basic disc molding (made from a carbon-fiber and polymer mix) is silicated in a special high-vacuum process at 3,092oF (1,700oC). Like Porsche's conventional discs, the PCCB parts are cross-drilled and directionally vented. A PCCB brake disc weighs 50% less than its cast-iron counterpart despite considerably larger dimensions. Like a competition-bred conventional system, the ceramic outer disc is mated to a steel inner "hat." PCCB brakes use specially developed six-piston calipers on the front and four-piston calipers on the rear.
Another key benefit of PCCB is its exceptional durability. While the actual rate of wear on all brake components--particularly pads and discs--is entirely dependent on individual driving style and vehicle usage, comparison testing reveals a much longer life expectancy with PCCB than with conventional braking systems, as long as 160,000 miles or more under normal driving conditions. It is important to note that racing and other extreme driving can significantly reduce the life expectancy of any vehicle component. After any driving event, have the vehicle, including all PCCB components, thoroughly checked and replaced as necessary.
Another key benefit of PCCB is its exceptional durability. While the actual rate of wear on all brake components--particularly pads and discs--is entirely dependent on individual driving style and vehicle usage, comparison testing reveals a much longer life expectancy with PCCB than with conventional braking systems, as long as 160,000 miles or more under normal driving conditions. It is important to note that racing and other extreme driving can significantly reduce the life expectancy of any vehicle component. After any driving event, have the vehicle, including all PCCB components, thoroughly checked and replaced as necessary.
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Carbon fiber - Ceramic brake technology
More article.
I wish they will make one for MINI soon, at affordable price, ofcourse.
What are ceramic brake systems?
It is all to do with the material the brake disks and pads are made of,
which at the moment tend to be grey-cast iron or a carbon/carbon compound?
The ceramic brakes, have a disk and pads which is made up of carbon-ceramic a ceramic composite material composed of carbon fibre within silicon Carbide matrix, so called carbon fibber reinforced silicon carbide.
These should not be mixed-up with ceramic coated brake pads for use on standard steel discs which are just high quality pads?
What are the advantages of ceramic brakes?
Carbon-ceramic brakes are much lighter than standard brakes, with a 65% advantage over standard components. This will improve the response and behaviour as the suspension weight is reduced and gives a reduction in unsprung masses.
The next obvious advantage would be their incredible stopping power, standard brakes such as carbon/carbon brakes do not reach there full capacity until they reach 300°c. at above 500°C. The carbon will react with the air and burn the outer layers creating were on the brake pads. However carbon-ceramic brakes are able to handle high brake temperatures with less heat fade, provide faster recovery after the stop, and generate less dust and wear on both the pads and discs. They also have very consistent frictional coefficients allowing them to maintain high standards of braking regardless of weather and temperature.
Another good trait of carbon/ ceramic brakes is that they give much quieter Braking. The ceramic compound helps to dampen the noise by creating a frequency beyond the human hearing range.
According to durability tests the life of ceramic brakes extend brake life compared to standard brake components without compromising braking performance, pad life and noise control.
The Mclaren Mercedes SLR which has ceramic brakes was recently tested and could stop in less distance from120 mph than it takes a normal car to stop from 60 mph which is about 400 feet/122 meters (dry condition).
So the disadvantages of ceramic brakes?
Well the only disadvantage of carbon-ceramic brakes is the fact that they are rather costly, but as with all these things, they will eventually fall in price and be more affordable to every one. There are companies out there that supply these brake systems but at a price.
The faster they make the cars go the better the brakes have to be i believe they have found the answer in, Carbon-ceramic braking systems.
It is all to do with the material the brake disks and pads are made of,
which at the moment tend to be grey-cast iron or a carbon/carbon compound?
The ceramic brakes, have a disk and pads which is made up of carbon-ceramic a ceramic composite material composed of carbon fibre within silicon Carbide matrix, so called carbon fibber reinforced silicon carbide.
These should not be mixed-up with ceramic coated brake pads for use on standard steel discs which are just high quality pads?
What are the advantages of ceramic brakes?
Carbon-ceramic brakes are much lighter than standard brakes, with a 65% advantage over standard components. This will improve the response and behaviour as the suspension weight is reduced and gives a reduction in unsprung masses.
The next obvious advantage would be their incredible stopping power, standard brakes such as carbon/carbon brakes do not reach there full capacity until they reach 300°c. at above 500°C. The carbon will react with the air and burn the outer layers creating were on the brake pads. However carbon-ceramic brakes are able to handle high brake temperatures with less heat fade, provide faster recovery after the stop, and generate less dust and wear on both the pads and discs. They also have very consistent frictional coefficients allowing them to maintain high standards of braking regardless of weather and temperature.
Another good trait of carbon/ ceramic brakes is that they give much quieter Braking. The ceramic compound helps to dampen the noise by creating a frequency beyond the human hearing range.
According to durability tests the life of ceramic brakes extend brake life compared to standard brake components without compromising braking performance, pad life and noise control.
The Mclaren Mercedes SLR which has ceramic brakes was recently tested and could stop in less distance from120 mph than it takes a normal car to stop from 60 mph which is about 400 feet/122 meters (dry condition).
So the disadvantages of ceramic brakes?
Well the only disadvantage of carbon-ceramic brakes is the fact that they are rather costly, but as with all these things, they will eventually fall in price and be more affordable to every one. There are companies out there that supply these brake systems but at a price.
The faster they make the cars go the better the brakes have to be i believe they have found the answer in, Carbon-ceramic braking systems.
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More article about the Carbon-Ceramic.
Using Ceramics, Brakes Are Light but Cost Is Heavy
By KEVIN CAMERON
Published: June 18, 2006
CHECKING boxes on an option list can quickly run up the price of a new car, but few add-ons are in the league of the ceramic brakes on a Ferrari F430: at $16,808, they cost about the same amount as a nicely equipped.
A cutaway of Audi's ceramic brake disc, which is lightweight but very expensive.
The high-tech brakes, an option on the $172,505 F430 but standard on some other Ferraris, are an upgrade for iron discs that already deliver impressive stopping power. Only those drivers who spend weekends on the racetrack are likely to notice a big difference in performance.
Car-savvy pedestrians may take note of the owner's selection, though. Instead of a metallic gleam visible through the spokes of the alloy wheels, they will see discs that look like patio stones.
Porsche was the first automaker to use ceramic brakes on a production car; in 2001, it offered discs made of a novel ceramic composite material to reduce the weight of a special sport model. Several Porsches now offer them as an option; on the Cayman sports car they cost $8,150.
Brake discs, also called rotors, of similar ceramic material are optional on the Audi S8 (although not yet in the United States). The $210,000 To view links in this forum your post count must be 10 or greater. Your post count is 0 momentarily. Diamond Series will also be equipped with ceramic discs.
Why replace metal discs, which have served well for many years and are easy to make? Using a ceramic composite takes advantage of a material with outstanding hardness (and potentially long life) and an ability to retain its strength and shape at temperatures that would melt conventional iron brake material into a glowing puddle.
Simple single-ingredient ceramics tend to be brittle like dinnerware, though some types work well in turbochargers or as bearings for jet engines. To make ceramics that are tough enough for a brake disc, the material is manufactured as a composite: strands of carbon fiber, which are highly resistant to stretching, are embedded in the material, using a process developed by the Mitsubishi Chemical Company.
Production begins with a disc-shaped "preform" of carbon fibers, essentially a bundle of woven cloth in the approximate shape of the finished disc. The preform is saturated with a liquid polymer containing carbon and silicon. It is then heated to convert the polymer into silicon carbide, an extremely hard ceramic. The finished surface looks like stone.
Today, ceramic brakes are of interest for their performance advantage — maintaining their stopping power even when extremely hot. But because ceramic discs will last four times as long as iron ones, according to automakers, their use could increase.
More important, ceramic discs weigh about half as much as iron discs — a valuable benefit for handling and acceleration.
There are other good reasons to seek lighter, more durable brake disc materials. Since the introduction of CAFE — the federally mandated corporate average fuel economy standards that an automaker's fleet of models must collectively meet— there has been strong pressure to reduce the weight of automobiles.
As a vehicle accelerates, its rotating parts require more energy to accelerate than nonrotating parts like seats or engine blocks. This is because they gain energy from both their accelerating forward motion and from their increasingly rapid rotation. This gives brake discs a special importance in fuel economy.
Because so much driving is stop-and-go, and because it takes more fuel to accelerate a heavy car than a light one, reducing weight can help automakers meet the CAFE standards. Heavy iron brake discs are a favorite target of weight-conscious auto engineers.
When a car is braked, friction between the disc and the pads that grip it converts the kinetic energy of forward motion to heat. The heat is absorbed mainly by the discs, and eventually dissipated to the surrounding air. The higher the speed, the more kinetic energy there is, and the hotter the brakes become.
As discs have been made lighter, their average operating temperature has risen, leading to more rapid pad and disc wear. Braking force increases with disc diameter, so any attempt to remove weight by reducing disc diameter also lengthens stopping distances. Carmakers sometimes compensate by installing higher-friction pads — which in turn may wear more rapidly.
Discs from the pre-CAFE era included extra material that allowed worn discs to be machined one or more times and re-used. Today's lighter discs have little extra; often, they must be replaced when worn.
Brake pads designed for use with ceramic composite discs may contain ceramic powder along with metal in the form of wire or particles. The ceramic provides the hardness to resist wear while the metal forms a so-called "transfer coating" on both the pad and the disc surfaces during the break-in period. Much of the friction generated between the pad and the disc occurs between and within these metallic films.
To permit safe brake operation at very high disc and pad temperatures, the hydraulic pistons, brake fluid and seals in the brake caliper must be insulated from the heat. This can be accomplished by installing heat shields, assuring good circulation of cooling air over the parts and blocking the path that the heat would travel.
Aircraft and Formula One racecars have the luxury of a more expensive solution: the carbon-carbon discs seen in dramatic racing photos, glowing red or even bright orange under hard braking. Discs and pads made of this material are able to operate routinely at temperatures that would melt most metals.
The carbon-carbon name is engineer-speak for a material consisting of two forms of carbon; crystalline carbon fibers of immense strength, reinforcing a structure of amorphous carbon (like the solid black carbon found in the brushes that carry electrical current in a motor or generator).
The carbon-carbon manufacturing process is enormously expensive — carbon-carbon discs cost thousands of dollars, but in racing their benefits are worth the price. Not only does braking improve, but the low weight of the disc mass lets the racecar accelerate slightly more quickly.
Such light discs can absorb large amounts of energy because their temperature can safely rise much higher than that of iron discs. Unfortunately, wear is fairly rapid and brake torque is limited at low disc temperature. Still, for aircraft, a pound of weight saved is a pound of payload (and revenue) gained, on every flight.
Ceramic composite disc materials are a big step in the right direction, costing only about one-fourth as much as carbon-carbon.
That may persuade more high-end automakers to offer ceramic brakes, which could help to reduce costs and make them available on more cars.
By KEVIN CAMERON
Published: June 18, 2006
CHECKING boxes on an option list can quickly run up the price of a new car, but few add-ons are in the league of the ceramic brakes on a Ferrari F430: at $16,808, they cost about the same amount as a nicely equipped.
A cutaway of Audi's ceramic brake disc, which is lightweight but very expensive.
The high-tech brakes, an option on the $172,505 F430 but standard on some other Ferraris, are an upgrade for iron discs that already deliver impressive stopping power. Only those drivers who spend weekends on the racetrack are likely to notice a big difference in performance.
Car-savvy pedestrians may take note of the owner's selection, though. Instead of a metallic gleam visible through the spokes of the alloy wheels, they will see discs that look like patio stones.
Porsche was the first automaker to use ceramic brakes on a production car; in 2001, it offered discs made of a novel ceramic composite material to reduce the weight of a special sport model. Several Porsches now offer them as an option; on the Cayman sports car they cost $8,150.
Brake discs, also called rotors, of similar ceramic material are optional on the Audi S8 (although not yet in the United States). The $210,000 To view links in this forum your post count must be 10 or greater. Your post count is 0 momentarily. Diamond Series will also be equipped with ceramic discs.
Why replace metal discs, which have served well for many years and are easy to make? Using a ceramic composite takes advantage of a material with outstanding hardness (and potentially long life) and an ability to retain its strength and shape at temperatures that would melt conventional iron brake material into a glowing puddle.
Simple single-ingredient ceramics tend to be brittle like dinnerware, though some types work well in turbochargers or as bearings for jet engines. To make ceramics that are tough enough for a brake disc, the material is manufactured as a composite: strands of carbon fiber, which are highly resistant to stretching, are embedded in the material, using a process developed by the Mitsubishi Chemical Company.
Production begins with a disc-shaped "preform" of carbon fibers, essentially a bundle of woven cloth in the approximate shape of the finished disc. The preform is saturated with a liquid polymer containing carbon and silicon. It is then heated to convert the polymer into silicon carbide, an extremely hard ceramic. The finished surface looks like stone.
Today, ceramic brakes are of interest for their performance advantage — maintaining their stopping power even when extremely hot. But because ceramic discs will last four times as long as iron ones, according to automakers, their use could increase.
More important, ceramic discs weigh about half as much as iron discs — a valuable benefit for handling and acceleration.
There are other good reasons to seek lighter, more durable brake disc materials. Since the introduction of CAFE — the federally mandated corporate average fuel economy standards that an automaker's fleet of models must collectively meet— there has been strong pressure to reduce the weight of automobiles.
As a vehicle accelerates, its rotating parts require more energy to accelerate than nonrotating parts like seats or engine blocks. This is because they gain energy from both their accelerating forward motion and from their increasingly rapid rotation. This gives brake discs a special importance in fuel economy.
Because so much driving is stop-and-go, and because it takes more fuel to accelerate a heavy car than a light one, reducing weight can help automakers meet the CAFE standards. Heavy iron brake discs are a favorite target of weight-conscious auto engineers.
When a car is braked, friction between the disc and the pads that grip it converts the kinetic energy of forward motion to heat. The heat is absorbed mainly by the discs, and eventually dissipated to the surrounding air. The higher the speed, the more kinetic energy there is, and the hotter the brakes become.
As discs have been made lighter, their average operating temperature has risen, leading to more rapid pad and disc wear. Braking force increases with disc diameter, so any attempt to remove weight by reducing disc diameter also lengthens stopping distances. Carmakers sometimes compensate by installing higher-friction pads — which in turn may wear more rapidly.
Discs from the pre-CAFE era included extra material that allowed worn discs to be machined one or more times and re-used. Today's lighter discs have little extra; often, they must be replaced when worn.
Brake pads designed for use with ceramic composite discs may contain ceramic powder along with metal in the form of wire or particles. The ceramic provides the hardness to resist wear while the metal forms a so-called "transfer coating" on both the pad and the disc surfaces during the break-in period. Much of the friction generated between the pad and the disc occurs between and within these metallic films.
To permit safe brake operation at very high disc and pad temperatures, the hydraulic pistons, brake fluid and seals in the brake caliper must be insulated from the heat. This can be accomplished by installing heat shields, assuring good circulation of cooling air over the parts and blocking the path that the heat would travel.
Aircraft and Formula One racecars have the luxury of a more expensive solution: the carbon-carbon discs seen in dramatic racing photos, glowing red or even bright orange under hard braking. Discs and pads made of this material are able to operate routinely at temperatures that would melt most metals.
The carbon-carbon name is engineer-speak for a material consisting of two forms of carbon; crystalline carbon fibers of immense strength, reinforcing a structure of amorphous carbon (like the solid black carbon found in the brushes that carry electrical current in a motor or generator).
The carbon-carbon manufacturing process is enormously expensive — carbon-carbon discs cost thousands of dollars, but in racing their benefits are worth the price. Not only does braking improve, but the low weight of the disc mass lets the racecar accelerate slightly more quickly.
Such light discs can absorb large amounts of energy because their temperature can safely rise much higher than that of iron discs. Unfortunately, wear is fairly rapid and brake torque is limited at low disc temperature. Still, for aircraft, a pound of weight saved is a pound of payload (and revenue) gained, on every flight.
Ceramic composite disc materials are a big step in the right direction, costing only about one-fourth as much as carbon-carbon.
That may persuade more high-end automakers to offer ceramic brakes, which could help to reduce costs and make them available on more cars.
Last edited by Maxicooper; Aug 17, 2007 at 10:43 AM.
Thread Starter
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6th Gear
Joined: Nov 2005
Posts: 3,911
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From: Ellicott City, MD
Back to the topic
This is also very interesting.
Will the new Carbon-ceramic material be the solution?
Rotors ...
Slotted or drilled ????
slotted rotors maintain approx. 96% of the friction surface
drilled rotors maintain approx. 85-93% of the friction surface
drilled and slotted only maintain 80-91% of the friction surface
For many years most racing rotors were drilled. There were two reasons -
the holes gave the "fireband" boundary layer of gasses and particulate
matter someplace to go and the edges of the holes gave the pad a better
"bite".
Unfortunately the drilled holes also reduced the thermal capacity of the
discs and served as very effective "stress raisers" significantly
decreasing disc life. Improvements in friction materials have pretty
much made the drilled rotor a thing of the past in racing. Most racing
rotors currently feature a series of tangential slots or channels that
serve the same purpose without the attendant disadvantages.
the process of drilling rotors and slotting rotors was done for 1 reason
and 1 reason only it is to disipate the gases that build up between the
pad and the rotor which occurs under extreme heat ( when braking very
aggressively like on a road course) and it has absolutely nothing to do
with heat disipation. the only way to transfer more heat away is by
using a larger heat sink which means use of a larger rotor whether in
diameter or thickness. Since the caliper will only allow for a certain
rotor thickness that solution is not very applicable because, if you are
changing tha caliper opening width you might as well get a larger rotor
diameter at that time
1) The brakes don't stop the vehicle - the tires do. The brakes slow the
rotation of the wheels and tires. This means that braking distance
measured on a single stop from a highway legal speed or higher is almost
totally dependent upon the stopping ability of the tires in use - which,
in the case of aftermarket advertising, may or may not be the ones
originally fitted to the car by the OE manufacturer.
2) The brakes function by converting the kinetic energy of the car into
thermal energy during deceleration - producing heat, lots of heat -
which must then be transferred into the surroundings and into the air
stream.
The amount of heat produced in context with a brake system needs to be
considered with reference to time meaning rate of work done or power.
Looking at only one side of a front brake assembly, the rate of work
done by stopping a 3500-pound car traveling at 100 Mph in eight seconds
is 30,600 calories/sec or 437,100 BTU/hr or is equivalent to 128 kW or
172 Hp. The disc dissipates approximately 80% of this energy. The ratio
of heat transfer among the three mechanisms is dependent on the
operating temperature of the system. The primary difference being the
increasing contribution of radiation as the temperature of the disc
rises. The contribution of the conductive mechanism is also dependent on
the mass of the disc and the attachment designs, with disc used for
racecars being typically lower in mass and fixed by mechanism that are
restrictive to conduction. At 1000oF the ratios on a racing 2-piece
annular disc design are 10% conductive, 45% convective, 45% radiation.
Similarly on a high performance street one-piece design, the ratios are
25% conductive, 25% convective, 50% radiation.
3) Repeated hard stops require both effective heat transfer and adequate
thermal storage capacity within the disc. The more disc surface area per
unit mass and the greater and more efficient the mass flow of air over
and through the disc, the faster the heat will be dissipated and the
more efficient the entire system will be. At the same time, the brake
discs must have enough thermal storage capacity to prevent distortion
and/or cracking from thermal stress until the heat can be dissipated.
This is not particularly important in a single stop but it is crucial in
the case of repeated stops from high speed - whether racing, touring or
towing.
4) Control and balance are at least as important as ultimate stopping
power. The objective of the braking system is to utilize the tractive
capacity of all of the tires to the maximum practical extent without
locking a tire. In order to achieve this, the braking force between the
front and rear tires must be nearly optimally proportioned even with ABS
equipped vehicles. At the same time, the required pedal pressure, pedal
travel and pedal firmness must allow efficient modulation by the driver.
5) Braking performance is about more than just brakes. In order for even
the best braking systems to function effectively, tires, suspension and
driving techniques must be optimized
Slotted or drilled ????
slotted rotors maintain approx. 96% of the friction surface
drilled rotors maintain approx. 85-93% of the friction surface
drilled and slotted only maintain 80-91% of the friction surface
For many years most racing rotors were drilled. There were two reasons -
the holes gave the "fireband" boundary layer of gasses and particulate
matter someplace to go and the edges of the holes gave the pad a better
"bite".
Unfortunately the drilled holes also reduced the thermal capacity of the
discs and served as very effective "stress raisers" significantly
decreasing disc life. Improvements in friction materials have pretty
much made the drilled rotor a thing of the past in racing. Most racing
rotors currently feature a series of tangential slots or channels that
serve the same purpose without the attendant disadvantages.
the process of drilling rotors and slotting rotors was done for 1 reason
and 1 reason only it is to disipate the gases that build up between the
pad and the rotor which occurs under extreme heat ( when braking very
aggressively like on a road course) and it has absolutely nothing to do
with heat disipation. the only way to transfer more heat away is by
using a larger heat sink which means use of a larger rotor whether in
diameter or thickness. Since the caliper will only allow for a certain
rotor thickness that solution is not very applicable because, if you are
changing tha caliper opening width you might as well get a larger rotor
diameter at that time
1) The brakes don't stop the vehicle - the tires do. The brakes slow the
rotation of the wheels and tires. This means that braking distance
measured on a single stop from a highway legal speed or higher is almost
totally dependent upon the stopping ability of the tires in use - which,
in the case of aftermarket advertising, may or may not be the ones
originally fitted to the car by the OE manufacturer.
2) The brakes function by converting the kinetic energy of the car into
thermal energy during deceleration - producing heat, lots of heat -
which must then be transferred into the surroundings and into the air
stream.
The amount of heat produced in context with a brake system needs to be
considered with reference to time meaning rate of work done or power.
Looking at only one side of a front brake assembly, the rate of work
done by stopping a 3500-pound car traveling at 100 Mph in eight seconds
is 30,600 calories/sec or 437,100 BTU/hr or is equivalent to 128 kW or
172 Hp. The disc dissipates approximately 80% of this energy. The ratio
of heat transfer among the three mechanisms is dependent on the
operating temperature of the system. The primary difference being the
increasing contribution of radiation as the temperature of the disc
rises. The contribution of the conductive mechanism is also dependent on
the mass of the disc and the attachment designs, with disc used for
racecars being typically lower in mass and fixed by mechanism that are
restrictive to conduction. At 1000oF the ratios on a racing 2-piece
annular disc design are 10% conductive, 45% convective, 45% radiation.
Similarly on a high performance street one-piece design, the ratios are
25% conductive, 25% convective, 50% radiation.
3) Repeated hard stops require both effective heat transfer and adequate
thermal storage capacity within the disc. The more disc surface area per
unit mass and the greater and more efficient the mass flow of air over
and through the disc, the faster the heat will be dissipated and the
more efficient the entire system will be. At the same time, the brake
discs must have enough thermal storage capacity to prevent distortion
and/or cracking from thermal stress until the heat can be dissipated.
This is not particularly important in a single stop but it is crucial in
the case of repeated stops from high speed - whether racing, touring or
towing.
4) Control and balance are at least as important as ultimate stopping
power. The objective of the braking system is to utilize the tractive
capacity of all of the tires to the maximum practical extent without
locking a tire. In order to achieve this, the braking force between the
front and rear tires must be nearly optimally proportioned even with ABS
equipped vehicles. At the same time, the required pedal pressure, pedal
travel and pedal firmness must allow efficient modulation by the driver.
5) Braking performance is about more than just brakes. In order for even
the best braking systems to function effectively, tires, suspension and
driving techniques must be optimized
6th Gear
Joined: May 2005
Posts: 15,478
Likes: 2
Any secret behind all of this?
Why do many of the exotic cars and super cars have used and still using drilled or slotted rotors?
Is it really just for show?
Since it's been proved that the solid rotor performs better, why are they still using them? Interesting, isn't it.
Umm.....
Why do many of the exotic cars and super cars have used and still using drilled or slotted rotors?
Is it really just for show?
Since it's been proved that the solid rotor performs better, why are they still using them? Interesting, isn't it.
Umm.....
See http://www.iwsti.com/forums/showthread.php?t=67007. This guy agrees with Maxi's quotes ... mostly bling. But read the following in reference to Porsche big reds:
"1) The holes are cast in giving a dense boundary layer-type crystalline grain structure around the hole at the microscopic level as opposed to drilling which cuts holes in the existing grain pattern leaving open endgrains, etc, just begging for cracks.
2) The holes are only 1/2 the diameter of the holes in most drilled rotors. This reduces the stress concentration factor due to hole interaction which is a function (not linear) of hole diameters and the distance between them.
3) Since the holes are only 1/2 as big they remove only 1/4 as much surface area and mass from the rotor faces as a larger hole. This does a couple of things:
It increases effective pad area compared with larger holes. The larger the pad area the cooler they will run, all else being equal. If the same amount of heat is generated over a larger surface area it will result in a lower temperature for both surfaces.
It increases the mass the rotor has to absorb heat with. If the same amount of heat is put into a rotor with a larger mass, it will result in a lower temperature.
3) The holes are placed along the vanes, actually cutting into them giving the vane a "half moon" cut along its width.
This is quite different from the standard drilled rotors you get from brembo/kvr/powerslot/"insert random ricer parts brand name here" brake rotors."
When your talking about true high powered sportscars capable of 180 plus and used as such in places like the autobahn, its a totally different world than US commuting speeds. Its also far different than full out race cars. You can't talk about race cars and street cars in the same breath.
You can probably take it to the bank if drilled rotors didn't do anything, Porsche rotors would not be cross drilled. For example, one test of all OEM Porsche rotors is that they must be capable of 62 mph to top speed, brake as hard as possible and back down to 62 mph 25 times in a row with NO FADE. (source) Try that with your common aftermarket BBK kits. The calipers themselves are monobloc made under contract by brembo. What other street cars have monobloc calipers? I dunno.
From what Ive read they cross-drilled for cooling, dispersing water (if I remember correctly). Reports I've read of people doing PCA racing or HPDE are that cracking can occur by spider web cracks between holes but is not all that common and unless there are a lot of big cracks, rotors are not routinely replaced.
The pics of the Ferrari and PCCBs are ceramics, a totally different beast and replacing a set of PCCBs cost more than a MCS cost ... seriously.
There are two main advantages. First, they simply do not fade. Probably never under street usage. They are also supposed to be very long lived, far longer than steel rotors. The first gen of PCCBs supposedly had problems with cracking. I think the general advice was don't do track time on PCCBs as they would not be covered under warranty. Todays second gen PCCBs may be better. A brake job is talking maybe $24K, enuff to get you a nice R56 althought the initial cost is a bargain in comparison.
The second advantage is weight. They weigh about 50% what steel brakes weigh. People who worry about unsprung weight may love them. However, I've also read that ppl who get PCCBs that need to be replaced, when reality sets it, just replace then with regular steel rotors. Until the prices come down to something palatable to buyers, if your going to drop $100 - $250K on a car, another $8K aint all that bad until reality sets in when its to replace them
However, the cool thing is they are YELLOW
So I think this comes down to who the high end car makers market their cars to and where they are intended to be driven. Obviously, buying a car capable of being driven 170 mph all day long may be pretty useless in the US. But when you consider a Porsche or Ferrari is intended to be driven that way, the cross drilled brakes have their place. The PCCBs more so simply because your talking about buyers who have the money and cars capable of 190+. Would you rather not have the best possible brakes available?
BTW, PCCBs are not new. They have been around for six years now and you do see them from time to tim in the marques.
Cross-drilled for a MINI? Probably overkill. But I'll keep my cross-drilled rotors. In normal use, Porsche overengineers their cars. For example,
"There's an old racing expression: "To finish first, first you must finish." Porsche doesn’t just pay homage to it, they live it. ... This phenomenal stamina is now built into every Porsche road car.
A while back, I was invited to speak to a local chapter of Porsche owners. I tried to explain the over-engineering that makes Porsche’s road cars so tough. For example, their engines and transmissions are built absurdly strong for their size. You will find more bearing area, big-ends and mains, for each liter of displacement in a 911 engine than in any other engine in production today. It’s an obscure technical point, but a telling one. You simply cannot buy a more robust high performance automobile. It’s a difference a skilled driver can feel. (source)
I may never be able to use the brakes as intended, but its nice to nice their capabilities are there. Sometimes people do not understand why they are prices so highly but overengineering is probably a reason. Maybe I get to Nevada again and do the silverstate
As to PCCBs, for the cost of PCCBs, I can buy an R56
. Not going to happen but I do know people who are looking for a take off set of PCCBs to put on their commuter/track car
Last edited by chows4us; Aug 17, 2007 at 02:30 PM.
Thread Starter
|
6th Gear
Joined: Nov 2005
Posts: 3,911
Likes: 0
From: Ellicott City, MD
Chows, good info indeed.
Here is another info:
Still $$$$$, but a little more affordable. .......
Here is another info:
Audi and SGL Carbon of Germany are reportedly involved in an effort to reduce the cost of manufacturing the brakes. Reports included no confirmation from Audi about its role in the project but quoted an SGL Carbon spokesman, who projected that the cost of a carbon disc could be reduced to about $465.
6th Gear
Joined: May 2005
Posts: 15,478
Likes: 2
BTW, here is what I meant about you can't compare a full on race car to a street car, even if the street car is meant for heavy track day usage
Here is a picture of a 997 GT3RSR ... American Lemans race car
http://www.seriouswheels.com/2006/20...e-1024x768.htm
Notice, not cross drilled
Now here is a picture of a 997 GT3RS
http://www.rsportscars.com/foto/05/gt3rs07_07.jpg
Cross drilled PCCBs. The GT3 is the basis of the racing series. GT3RS is the "lightweight" version of the GT3 and the GT3RSR is the racing version.
Different brakes for different purposes. Why not PCCBs? Probably the cracking issue at the track. Can't take the stress yet?
Here is a picture of a 997 GT3RSR ... American Lemans race car
http://www.seriouswheels.com/2006/20...e-1024x768.htm
Notice, not cross drilled
Now here is a picture of a 997 GT3RS
http://www.rsportscars.com/foto/05/gt3rs07_07.jpg
Cross drilled PCCBs. The GT3 is the basis of the racing series. GT3RS is the "lightweight" version of the GT3 and the GT3RSR is the racing version.
Different brakes for different purposes. Why not PCCBs? Probably the cracking issue at the track. Can't take the stress yet?
6th Gear
Joined: May 2005
Posts: 15,478
Likes: 2
It looks like SLG makes the PCCBs. Your quote is from here
in 12/06. Haven't heard a thing about this and while prices are slowly coming around, the absolute cheapest I have seen for a set of PCCBs are $14K lately. Calipers are also monobloc.
The pics I've seen show GT3RSR using steel. Specs say internally vented. 6 piston fronts, 4 piston rears
Any Porsche can be ordered with PCCBs (carbon-ceramic) as an option. Steel is standard albeit in larger sizes (e.g., 4 piston vice 6 piston) for the more powerful cars. I think only the GT came with PCCB standard but they are out of production.
I had also heard a rumour that they weren't making PCCBs anymore but it turned out to be more like they ran OUT of PCCBs. Many people ordering GT3s and TTs get the PCCBs. Again, if your buying a $140K car, another $8K is probably pocket change to them
If your really racing, your accelerating as hard as you possible can and decelerating as hard as you possibly can. I always give credit to endurance race car drivers, they are doing hard work, its not fun driving, they are working. The stresses are far different than doing a few 45 minute DE events or normal US driving ... and so different tools for different jobs.
Last edited by chows4us; Aug 17, 2007 at 03:29 PM.
6th Gear
Joined: May 2005
Posts: 15,478
Likes: 2
I guess I should add I bought the JCW brakes. Did they do anything? Nothing I could feel. The JCW suspension you could feel, it was softer than stock.
I fell into the trap many ppl do, gotta mod, gotta spend money. If I had it to do over, I would not have done it for a street car, total waste of money (other than as bling). I consider it a lesson learned
And, knowledgable people who raced MINIs told me that brakes were not a problem but rubber was (getting power to the ground). But did I listen? Of course not
After checking some sources, I see several ppl saying cross drilled is about the rain. Not good for the track. Much better at water dispersal in the rain.
I fell into the trap many ppl do, gotta mod, gotta spend money. If I had it to do over, I would not have done it for a street car, total waste of money (other than as bling). I consider it a lesson learned
And, knowledgable people who raced MINIs told me that brakes were not a problem but rubber was (getting power to the ground). But did I listen? Of course notAfter checking some sources, I see several ppl saying cross drilled is about the rain. Not good for the track. Much better at water dispersal in the rain.
Last edited by chows4us; Aug 17, 2007 at 04:09 PM.
chows4us,
I don't see how the point that Porsche uses cross drilling justifies those rotors. Afterall, they're just another car company, selling in the luxury market.
I have heard this many, many places but a lot of people have disputed this fact. There was a thread on another high performance car board where (I believe, it's been awhile since I read it) a metal engineer offered a cash reward for someone to prove this point to him, and no one could without a doubt prove the cast in claim made for Porsche's rotors. Please, I'd like to be proven wrong on this, but I can't find conclusive evidence that they are cast.
2) The holes are only 1/2 the diameter of the holes in most drilled rotors. This reduces the stress concentration factor due to hole interaction which is a function (not linear) of hole diameters and the distance between them.
3) Since the holes are only 1/2 as big they remove only 1/4 as much surface area and mass from the rotor faces as a larger hole. This does a couple of things:
It increases effective pad area compared with larger holes. The larger the pad area the cooler they will run, all else being equal. If the same amount of heat is generated over a larger surface area it will result in a lower temperature for both surfaces.
It increases the mass the rotor has to absorb heat with. If the same amount of heat is put into a rotor with a larger mass, it will result in a lower temperature.
3) The holes are placed along the vanes, actually cutting into them giving the vane a "half moon" cut along its width.
This is quite different from the standard drilled rotors you get from brembo/kvr/powerslot/"insert random ricer parts brand name here" brake rotors."
None of these points show how cross drilled are better than solid or slotted. All it claims is that Porsche cross drilled are better than no-name cross drilled. I don't think many would dispute that.
When your talking about true high powered sportscars capable of 180 plus and used as such in places like the autobahn, its a totally different world than US commuting speeds. Its also far different than full out race cars. You can't talk about race cars and street cars in the same breath.
You can probably take it to the bank if drilled rotors didn't do anything, Porsche rotors would not be cross drilled. For example, one test of all OEM Porsche rotors is that they must be capable of 62 mph to top speed, brake as hard as possible and back down to 62 mph 25 times in a row with NO FADE. (source) Try that with your common aftermarket BBK kits. The calipers themselves are monobloc made under contract by brembo. What other street cars have monobloc calipers? I dunno.
"For example, one test of all OEM Porsche rotors is that they must be capable of 62 mph to top speed, brake as hard as possible and back down to 62 mph 25 times in a row with NO FADE. (source) Try that with your common aftermarket BBK kits. " How does this support cross drilled rotors either? There are hundreds of variances between high performance brakes, not to mention cooling methods in place on the car. I don't think that test shows cross drilling works.
From what Ive read they cross-drilled for cooling, dispersing water (if I remember correctly). Reports I've read of people doing PCA racing or HPDE are that cracking can occur by spider web cracks between holes but is not all that common and unless there are a lot of big cracks, rotors are not routinely replaced.
The pics of the Ferrari and PCCBs are ceramics, a totally different beast and replacing a set of PCCBs cost more than a MCS cost ... seriously.
There are two main advantages. First, they simply do not fade. Probably never under street usage. They are also supposed to be very long lived, far longer than steel rotors. The first gen of PCCBs supposedly had problems with cracking. I think the general advice was don't do track time on PCCBs as they would not be covered under warranty. Todays second gen PCCBs may be better. A brake job is talking maybe $24K, enuff to get you a nice R56 althought the initial cost is a bargain in comparison.
The second advantage is weight. They weigh about 50% what steel brakes weigh. People who worry about unsprung weight may love them. However, I've also read that ppl who get PCCBs that need to be replaced, when reality sets it, just replace then with regular steel rotors. Until the prices come down to something palatable to buyers, if your going to drop $100 - $250K on a car, another $8K aint all that bad until reality sets in when its to replace them
However, the cool thing is they are YELLOW
So I think this comes down to who the high end car makers market their cars to and where they are intended to be driven. Obviously, buying a car capable of being driven 170 mph all day long may be pretty useless in the US. But when you consider a Porsche or Ferrari is intended to be driven that way, the cross drilled brakes have their place. The PCCBs more so simply because your talking about buyers who have the money and cars capable of 190+. Would you rather not have the best possible brakes available?
I still don't see how you've proven that cross drilling is the best, aside from saying that Porsche and Ferrari have no motives other than pure performance. They are luxury car makers because of the price tag, and people who buy them may be looking at AMGs with cross drilling. Porsche keeps up with the marketing to sell cars. Surely you're not going to argue that the mandatory nav screen in the new 911s is purely there to make the car go faster around the track.
And as for the best brakes available, then we would be talking reinforced carbon carbon brakes...made from the same stuff that covers the leading wing tips of the space shuttle.
So they overengineer there cars...what does that prove about cross-drilled brakes? They're also driven by the bottom line, by market forces and competition. Porsche has never needed to borrow to run its company, a feat in the auto industry, and I doubt that is simply because of overengineering. Porsche marketing is a strong, strong factor in its success and its certainly possible that they had a hand in the cross drilled design.
I may never be able to use the brakes as intended, but its nice to nice their capabilities are there. Sometimes people do not understand why they are prices so highly but overengineering is probably a reason. Maybe I get to Nevada again and do the silverstate
As to PCCBs, for the cost of PCCBs, I can buy an R56. Not going to happen but I do know people who are looking for a take off set of PCCBs to put on their commuter/track car
Listen, I don't know the truth. But I do know that every brake expert I have spoken to and numerous respected companies have all agreed that cross drilling is useless in this day and age. It's a marketing ploy, they say. I don't think Porsche is above this, and I don't really see any evidence to support that.
As for the water disperal points, I wonder about the validity of this, too. The only positive aspects associated with cross drilling that I've heard from reputable soruces is related to out gassing (which is no longer a problem). The water thing seems to be something everyone talks about, but I'd really like to see some hard info on this point. Again, I don't know the truth, but the argument against cross drilled seems mighty strong to me and I'm looking for someone to counter with some strong arguments, but it doesn't seem to happen.
I don't see how the point that Porsche uses cross drilling justifies those rotors. Afterall, they're just another car company, selling in the luxury market.
For most cars, I agree. For the cars Maxi is showing, I disagree.
See http://www.iwsti.com/forums/showthread.php?t=67007. This guy agrees with Maxi's quotes ... mostly bling. But read the following in reference to Porsche big reds:
"1) The holes are cast in giving a dense boundary layer-type crystalline grain structure around the hole at the microscopic level as opposed to drilling which cuts holes in the existing grain pattern leaving open endgrains, etc, just begging for cracks.
See http://www.iwsti.com/forums/showthread.php?t=67007. This guy agrees with Maxi's quotes ... mostly bling. But read the following in reference to Porsche big reds:
"1) The holes are cast in giving a dense boundary layer-type crystalline grain structure around the hole at the microscopic level as opposed to drilling which cuts holes in the existing grain pattern leaving open endgrains, etc, just begging for cracks.
2) The holes are only 1/2 the diameter of the holes in most drilled rotors. This reduces the stress concentration factor due to hole interaction which is a function (not linear) of hole diameters and the distance between them.
3) Since the holes are only 1/2 as big they remove only 1/4 as much surface area and mass from the rotor faces as a larger hole. This does a couple of things:
It increases effective pad area compared with larger holes. The larger the pad area the cooler they will run, all else being equal. If the same amount of heat is generated over a larger surface area it will result in a lower temperature for both surfaces.
It increases the mass the rotor has to absorb heat with. If the same amount of heat is put into a rotor with a larger mass, it will result in a lower temperature.
3) The holes are placed along the vanes, actually cutting into them giving the vane a "half moon" cut along its width.
This is quite different from the standard drilled rotors you get from brembo/kvr/powerslot/"insert random ricer parts brand name here" brake rotors."
When your talking about true high powered sportscars capable of 180 plus and used as such in places like the autobahn, its a totally different world than US commuting speeds. Its also far different than full out race cars. You can't talk about race cars and street cars in the same breath.
You can probably take it to the bank if drilled rotors didn't do anything, Porsche rotors would not be cross drilled. For example, one test of all OEM Porsche rotors is that they must be capable of 62 mph to top speed, brake as hard as possible and back down to 62 mph 25 times in a row with NO FADE. (source) Try that with your common aftermarket BBK kits. The calipers themselves are monobloc made under contract by brembo. What other street cars have monobloc calipers? I dunno.
From what Ive read they cross-drilled for cooling, dispersing water (if I remember correctly). Reports I've read of people doing PCA racing or HPDE are that cracking can occur by spider web cracks between holes but is not all that common and unless there are a lot of big cracks, rotors are not routinely replaced.
The pics of the Ferrari and PCCBs are ceramics, a totally different beast and replacing a set of PCCBs cost more than a MCS cost ... seriously.
There are two main advantages. First, they simply do not fade. Probably never under street usage. They are also supposed to be very long lived, far longer than steel rotors. The first gen of PCCBs supposedly had problems with cracking. I think the general advice was don't do track time on PCCBs as they would not be covered under warranty. Todays second gen PCCBs may be better. A brake job is talking maybe $24K, enuff to get you a nice R56 althought the initial cost is a bargain in comparison.
The second advantage is weight. They weigh about 50% what steel brakes weigh. People who worry about unsprung weight may love them. However, I've also read that ppl who get PCCBs that need to be replaced, when reality sets it, just replace then with regular steel rotors. Until the prices come down to something palatable to buyers, if your going to drop $100 - $250K on a car, another $8K aint all that bad until reality sets in when its to replace them
However, the cool thing is they are YELLOW
So I think this comes down to who the high end car makers market their cars to and where they are intended to be driven. Obviously, buying a car capable of being driven 170 mph all day long may be pretty useless in the US. But when you consider a Porsche or Ferrari is intended to be driven that way, the cross drilled brakes have their place. The PCCBs more so simply because your talking about buyers who have the money and cars capable of 190+. Would you rather not have the best possible brakes available?
And as for the best brakes available, then we would be talking reinforced carbon carbon brakes...made from the same stuff that covers the leading wing tips of the space shuttle.
BTW, PCCBs are not new. They have been around for six years now and you do see them from time to tim in the marques.
Cross-drilled for a MINI? Probably overkill. But I'll keep my cross-drilled rotors. In normal use, Porsche overengineers their cars. For example,
"There's an old racing expression: "To finish first, first you must finish." Porsche doesn’t just pay homage to it, they live it. ... This phenomenal stamina is now built into every Porsche road car.
A while back, I was invited to speak to a local chapter of Porsche owners. I tried to explain the over-engineering that makes Porsche’s road cars so tough. For example, their engines and transmissions are built absurdly strong for their size. You will find more bearing area, big-ends and mains, for each liter of displacement in a 911 engine than in any other engine in production today. It’s an obscure technical point, but a telling one. You simply cannot buy a more robust high performance automobile. It’s a difference a skilled driver can feel. (source)
Cross-drilled for a MINI? Probably overkill. But I'll keep my cross-drilled rotors. In normal use, Porsche overengineers their cars. For example,
"There's an old racing expression: "To finish first, first you must finish." Porsche doesn’t just pay homage to it, they live it. ... This phenomenal stamina is now built into every Porsche road car.
A while back, I was invited to speak to a local chapter of Porsche owners. I tried to explain the over-engineering that makes Porsche’s road cars so tough. For example, their engines and transmissions are built absurdly strong for their size. You will find more bearing area, big-ends and mains, for each liter of displacement in a 911 engine than in any other engine in production today. It’s an obscure technical point, but a telling one. You simply cannot buy a more robust high performance automobile. It’s a difference a skilled driver can feel. (source)
I may never be able to use the brakes as intended, but its nice to nice their capabilities are there. Sometimes people do not understand why they are prices so highly but overengineering is probably a reason. Maybe I get to Nevada again and do the silverstate
As to PCCBs, for the cost of PCCBs, I can buy an R56
. Not going to happen but I do know people who are looking for a take off set of PCCBs to put on their commuter/track carListen, I don't know the truth. But I do know that every brake expert I have spoken to and numerous respected companies have all agreed that cross drilling is useless in this day and age. It's a marketing ploy, they say. I don't think Porsche is above this, and I don't really see any evidence to support that.
As for the water disperal points, I wonder about the validity of this, too. The only positive aspects associated with cross drilling that I've heard from reputable soruces is related to out gassing (which is no longer a problem). The water thing seems to be something everyone talks about, but I'd really like to see some hard info on this point. Again, I don't know the truth, but the argument against cross drilled seems mighty strong to me and I'm looking for someone to counter with some strong arguments, but it doesn't seem to happen.
Race series rules could also be at play. Generally, GT car races are organized with an eye towards keeping costs low. This could certainly be a factor.
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6th Gear
Joined: Nov 2005
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From: Ellicott City, MD
JCW drilled/slotted discs
So the cracking is really not the main issue after all, but wasting money without any gain is. (except bling factor )
Back to JCW drilled/slotted discs, since its directly from factory and will be covered under their warranty (as long as you still have the maintenace plan, the one that also cover brake), this shouldn't be a problem, Am I correct?. If in case that we only do autox couple of times a year, road track once a year, some spirited driving every now and then and want to have another bling on your car. So if we're not going too extreme, these JCW rotors should work just fine, right?
One thing that's surprised me, you've mentioned that you did not feel any different from JCW brake upgrade on R53, since the rotor is slightly larger and brake pads are supposed to be better.
)Back to JCW drilled/slotted discs, since its directly from factory and will be covered under their warranty (as long as you still have the maintenace plan, the one that also cover brake), this shouldn't be a problem, Am I correct?. If in case that we only do autox couple of times a year, road track once a year, some spirited driving every now and then and want to have another bling on your car.
So if we're not going too extreme, these JCW rotors should work just fine, right?One thing that's surprised me, you've mentioned that you did not feel any different from JCW brake upgrade on R53, since the rotor is slightly larger and brake pads are supposed to be better.
