Cross Drilled Rotors
May 20, 2004 | 07:58 PM
#1
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Cross Drilled Rotors
Here is the write-up you all asked for. Our of respect for whoever that supporter was, it is in a seperate thread and furthermore I would like to clearly state that this is not an attack on him personally, his buisness, or anything of that nature. Simply a technical "article" addressing an issue.
Origin of Cross drilled rotors
They used crossed drilled rotors "back in the day" when brake pads out gassed. Pads under extreme heat and pressure (like when all the energy of a 4000lb object at 60mph was turned into heat energy) would produced gasses. These gasses created a "layer" between the rotor and pad which prevented or at least reduced pad to rotor friction. Cross drilling provided a pathway for which these gasses could escape. Pads today do not do this unless you are buying cheap $4.78 napa pads
left right up down, lets clarify
For refereance, lets set up a coordinate system for the rotor. Imagine the rotor is flat on your monitor, rotor hat facing you. (like you removed the wheel on this drawing-http://www.worldisround.com/articles/27745/photo96.html) Now when I say left or up or down or into the page; we are on the same page (pun intended)
Why they do not cool
Some make the arguement that dross driling increases surface area. This may or may not be true depending on the diamter of the holes and the thickness of the plates. However the important thing to keep in mind is that air doe not want to flow into the page or out of the page. It has no momentum in that direction. Some will make it through due to turbulence and such but there is more air going from the left to the right and at a faster rate. the air in there is stagnant compared to that of the air on the braking surface.
so what cools it?
The vents do most of the cooling. There is a **** ton of money dumped into the design of the vents every rear. Bullet style is newest thing out there right there now. These work like a centrifical fan moving air up./down through the middle of the rotor. Again, little to no air going out of the page but there is air moving up/down the page and left/right.
How they actually hurt braking
With a smaller braking surface (significantly reduced) you get less braking. pretty simple. Holes = less surface area.
I did some quick calculations and found that with a 1/4 inch hole; about 100 holes would lose 1.2lbs Ohh boy. a whole freaking 4.8 lbs off a 5000lb truck. Its not as bad as wheels either because its not that far from the center. Take a crap or something. Clean your air filter.
BUT; 100 holes at 1/4 inch on a 3inch braking surface "ring" on a 13 inch rotor (thats a big rotor) means 20% of the surface area is gone. Whoops.
Also, with less weight comes less thermal mass. The same heat has to go into less metal that has a harder time cooling itself to begin with! So now you have a hight heat "density." in the rotor. Brake fade is a bitch. The outboard rotor has much easier time staying cool compared to the inboard/inside one because it is much heavier/more mass (rotor hat).
Also, more heat = more warping and cracking. Holes = great place for metal to start to warp. The metal will being it warp out of the page around the holes like a volcano on the outer braking surface (and into the page on the back braking surface). Insides too. THIS will eat your rotors.
Crappy OEM rotors are made so that the tickness VARIATION between braking surfaces is not more than 0.004 inches. Yes, four Ten-Thousanths of an inch! And this does mean one side has to be +-0.004''
If you are looking sideways at the rotor plates(into the side of your monitor) and "zoom in" you enough you will see that the plates are "wavey" and not flat. you just cant machine things to be perfect. extreme tolerances to the point where you can rub two peices of metal together by hadn and they will stick yes, but still not perfect.
Anyway, these "waves" can not line up to have a greater differences of .004'' at their EXTREMES. It is like having a +-.001'' tolerence on the plates. Now you get this "volcanoing" going on and it will EAT your pads.
Holes are also a great place for cracks to form unless you cast them in there (really effing expensive because there are practically 2 ways to cast iron; sand and ceramic) Rotors are predominantly sand cast so its a bit PITA to sand cast them with holes especially since you would have to line them up perfectly so that the holes dont overlap the vents. there are almost always a prime number of vents inside a rotor and to keep things balanced, you need to blanced with the holes as well. Its a really big PITA for low production units. Its why porsche charges $12,000 for the upgrade. Its mainly because suckers buy their cars though. They would be really upset if they paid $12k and didn't get holes cut in their rotors. Now they look cooler. Its mainly the caliper doing the work in there and maybe the increased leverage of a larger rotor. I hear porsche is casting salt inside their rotors to absorb head in some exotics as well. True? No clue.
The ideal brake system should have great airflow to the rotor, particuallary the inside/backside one since it does not have a rotor hat to absorb heat. It should have strong calipers with large braking surface, floating calipers are nice but $$$ and higher maintinance. Steel braided lines will increase pedal feel and reduce the expanding of the rubber lines that cause this. Good fluid is a plus. An aluminum hat does a great job of disipating heat but i wonder about the strength A larger rotor has more surface area and more leverage to stop. Brake calipers are "upside down" on the very bottom of the wheel to lower center of gravity on the vehicle. Pads should be chosen for the correct heat range the vehicle will see. However road debris, packaging, a need to be interchangable, wheel size, cost, ect play a role in all of this.
Nit picks (other than spelling?)
Origin of Cross drilled rotors
They used crossed drilled rotors "back in the day" when brake pads out gassed. Pads under extreme heat and pressure (like when all the energy of a 4000lb object at 60mph was turned into heat energy) would produced gasses. These gasses created a "layer" between the rotor and pad which prevented or at least reduced pad to rotor friction. Cross drilling provided a pathway for which these gasses could escape. Pads today do not do this unless you are buying cheap $4.78 napa pads
left right up down, lets clarify
For refereance, lets set up a coordinate system for the rotor. Imagine the rotor is flat on your monitor, rotor hat facing you. (like you removed the wheel on this drawing-http://www.worldisround.com/articles/27745/photo96.html) Now when I say left or up or down or into the page; we are on the same page (pun intended)
Why they do not cool
Some make the arguement that dross driling increases surface area. This may or may not be true depending on the diamter of the holes and the thickness of the plates. However the important thing to keep in mind is that air doe not want to flow into the page or out of the page. It has no momentum in that direction. Some will make it through due to turbulence and such but there is more air going from the left to the right and at a faster rate. the air in there is stagnant compared to that of the air on the braking surface.
so what cools it?
The vents do most of the cooling. There is a **** ton of money dumped into the design of the vents every rear. Bullet style is newest thing out there right there now. These work like a centrifical fan moving air up./down through the middle of the rotor. Again, little to no air going out of the page but there is air moving up/down the page and left/right.
How they actually hurt braking
With a smaller braking surface (significantly reduced) you get less braking. pretty simple. Holes = less surface area.
I did some quick calculations and found that with a 1/4 inch hole; about 100 holes would lose 1.2lbs Ohh boy. a whole freaking 4.8 lbs off a 5000lb truck. Its not as bad as wheels either because its not that far from the center. Take a crap or something. Clean your air filter.
BUT; 100 holes at 1/4 inch on a 3inch braking surface "ring" on a 13 inch rotor (thats a big rotor) means 20% of the surface area is gone. Whoops.
Also, with less weight comes less thermal mass. The same heat has to go into less metal that has a harder time cooling itself to begin with! So now you have a hight heat "density." in the rotor. Brake fade is a bitch. The outboard rotor has much easier time staying cool compared to the inboard/inside one because it is much heavier/more mass (rotor hat).
Also, more heat = more warping and cracking. Holes = great place for metal to start to warp. The metal will being it warp out of the page around the holes like a volcano on the outer braking surface (and into the page on the back braking surface). Insides too. THIS will eat your rotors.
Crappy OEM rotors are made so that the tickness VARIATION between braking surfaces is not more than 0.004 inches. Yes, four Ten-Thousanths of an inch! And this does mean one side has to be +-0.004''
If you are looking sideways at the rotor plates(into the side of your monitor) and "zoom in" you enough you will see that the plates are "wavey" and not flat. you just cant machine things to be perfect. extreme tolerances to the point where you can rub two peices of metal together by hadn and they will stick yes, but still not perfect.
Anyway, these "waves" can not line up to have a greater differences of .004'' at their EXTREMES. It is like having a +-.001'' tolerence on the plates. Now you get this "volcanoing" going on and it will EAT your pads.
Holes are also a great place for cracks to form unless you cast them in there (really effing expensive because there are practically 2 ways to cast iron; sand and ceramic) Rotors are predominantly sand cast so its a bit PITA to sand cast them with holes especially since you would have to line them up perfectly so that the holes dont overlap the vents. there are almost always a prime number of vents inside a rotor and to keep things balanced, you need to blanced with the holes as well. Its a really big PITA for low production units. Its why porsche charges $12,000 for the upgrade. Its mainly because suckers buy their cars though. They would be really upset if they paid $12k and didn't get holes cut in their rotors. Now they look cooler. Its mainly the caliper doing the work in there and maybe the increased leverage of a larger rotor. I hear porsche is casting salt inside their rotors to absorb head in some exotics as well. True? No clue.
The ideal brake system should have great airflow to the rotor, particuallary the inside/backside one since it does not have a rotor hat to absorb heat. It should have strong calipers with large braking surface, floating calipers are nice but $$$ and higher maintinance. Steel braided lines will increase pedal feel and reduce the expanding of the rubber lines that cause this. Good fluid is a plus. An aluminum hat does a great job of disipating heat but i wonder about the strength A larger rotor has more surface area and more leverage to stop. Brake calipers are "upside down" on the very bottom of the wheel to lower center of gravity on the vehicle. Pads should be chosen for the correct heat range the vehicle will see. However road debris, packaging, a need to be interchangable, wheel size, cost, ect play a role in all of this.
Nit picks (other than spelling?)
May 20, 2004 | 08:10 PM
#3
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copy, paste, double space, big font, 12.5, take a bit off each margin and I kept a lot of stuff out that wasn't really needed. No diagrams either. Engineering reports are full of them
May 20, 2004 | 08:11 PM
#4
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Meh, mine work at least as good as stock, even though i'm sure a good portion of that is pads. If nothing else, they look prettier than stock.
May 20, 2004 | 08:12 PM
#5
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From: Dallas, North Mexico
want to simulate a few more miles? Put 1500# in the bed and stap on a trailor and stop on a downhill. Promise my rotors will be in better shape than yours.
May 20, 2004 | 08:15 PM
#6
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BTW, here is a counterpoint to your discussion. YMMV
http://www.precisionbrakescompany.com/why.asp
http://www.precisionbrakescompany.com/faq.asp
http://www.precisionbrakescompany.com/why.asp
http://www.precisionbrakescompany.com/faq.asp
May 20, 2004 | 08:26 PM
#7
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From: Dallas, North Mexico
Originally Posted by LOW2000
BTW, here is a counterpoint to your discussion. YMMV
http://www.precisionbrakescompany.com/why.asp
http://www.precisionbrakescompany.com/faq.asp
http://www.precisionbrakescompany.com/why.asp
http://www.precisionbrakescompany.com/faq.asp
Hey, they took the word gullible out of the dictionary. Id tell your girlfriend my **** was the fountain of youth if it would convince her to suck it.
http://www.baer.com/Support/FAQ.aspx
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 began to break down at extreme temperatures. This condition is often referred to as “green pad fade” or “outgassing”. When it does occur, the driver still has a good firm brake pedal, but simply little or no friction. Since this normally happens only at temperatures witnessed in racing, this can be very exciting!
However, with today’s race pad technology, ‘outgassing’ is no longer much of a concern. When shopping for races pads, or even ultra-high performance road pads, look for the phrases, “dynamic surface treatment”, “race ready”, and/or, “pre-burnished”. When these or similar statements are made by the pad manufacturer, the pad in question will likely have little or no problem with ‘outgassing’. Ironically more pedestrian pads used on most streetcars will still exhibit ‘outgassing’, but only when used at temperatures normally only encountered on the racetrack.
Although crossdrilling and/or slotting will provide a welcome path to expend any gasses when and if they develop, it is primarily a visual enhancement behind today’s often wide-open wheel designs.
Crossdrilling offers the greatest gas relief pathway, but creates potential “stress risers” from which cracks can occur. Baer’s rotors are cast with crossdrilling in mind, from the material specified, to curved vanes, behind which the holes are placed to minimize potential crack migration. Slotted surfaces are what Baer recommends for track only use. Slotted only rotors are offered as an option for any of Baer’s offerings.
However, with today’s race pad technology, ‘outgassing’ is no longer much of a concern. When shopping for races pads, or even ultra-high performance road pads, look for the phrases, “dynamic surface treatment”, “race ready”, and/or, “pre-burnished”. When these or similar statements are made by the pad manufacturer, the pad in question will likely have little or no problem with ‘outgassing’. Ironically more pedestrian pads used on most streetcars will still exhibit ‘outgassing’, but only when used at temperatures normally only encountered on the racetrack.
Although crossdrilling and/or slotting will provide a welcome path to expend any gasses when and if they develop, it is primarily a visual enhancement behind today’s often wide-open wheel designs.
Crossdrilling offers the greatest gas relief pathway, but creates potential “stress risers” from which cracks can occur. Baer’s rotors are cast with crossdrilling in mind, from the material specified, to curved vanes, behind which the holes are placed to minimize potential crack migration. Slotted surfaces are what Baer recommends for track only use. Slotted only rotors are offered as an option for any of Baer’s offerings.
http://www.wilwood.com/faq.asp#question7
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.
Slots or grooves in rotor faces are partly a carryover from the days of asbestos pads. Asbestos and other organic pads were prone to "glazing" and the slots tended to help "scrape or de-glaze" them. Drilling and slotting rotors has become popular in street applications for their pure aesthetic value. Wilwood has a large selection of drilled and slotted rotors for a wide range of applications
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.
Slots or grooves in rotor faces are partly a carryover from the days of asbestos pads. Asbestos and other organic pads were prone to "glazing" and the slots tended to help "scrape or de-glaze" them. Drilling and slotting rotors has become popular in street applications for their pure aesthetic value. Wilwood has a large selection of drilled and slotted rotors for a wide range of applications
http://web.camaross.com/forums/showt...ghlight=brakes
Trending Topics
May 20, 2004 | 08:29 PM
#8
Why should you upgrade to cross drilled rotors?
Simply stated, the function of any vehicles brake system is to stop the vehicle. This is accomplished by absorbing the kinetic energy stored in the moving vehicle, and converting it into heat. The friction caused by the brake pad rubbing on the rotor is the source of this heat. The more quickly and efficiently that heat can be absorbed and dissipated, the more quickly and efficiently the car will stop.
There are several contributing factors to this heat reduction. One of the most common sources of heat is from the gases produced by the bonding agents of the brake pad burning off. Under severe braking, this can actually produce a boundary layer of gas that pushes the pad away from the rotor, which can lead to excessive brake fade. The cross-drilled holes or slots in a rotor provide an escape path for these gasses (de-gassing or out-gassing are common terms), and allow the pad to stay in contact with the rotor. As well as de-gassing, cross drilling or slotting will provide better wet weather braking as water is swept through the holes, or down the slots.
A vented rotor can be viewed as an air fan. When in motion, the vents draw air from the center of the rotor outward. This air flow, over an increased internal surface area, effectively dissipates rotor heat. Cross drilling adds to this air flow, as well as providing additional rotor surface cooling.
I would like you to explain how the following car/motorcycle manufactures are putting inferior brake systems on the road:
Mercedes Benz
Chevrolet
Ferrari
Porsche
Harley Davidson
FORD
Saleen
Kawasaki
Yamaha
Buell
Honda
Rolls Royce
Aston Martin
BMW
Bugatti
Lamborghini
Lotus
Vector
I could go on, but I am sure you see my point. BTW drilling and slotting are not for cooling, it is for pulling the gasses created by braking away from the surface where it will cause brake fade.
Simply stated, the function of any vehicles brake system is to stop the vehicle. This is accomplished by absorbing the kinetic energy stored in the moving vehicle, and converting it into heat. The friction caused by the brake pad rubbing on the rotor is the source of this heat. The more quickly and efficiently that heat can be absorbed and dissipated, the more quickly and efficiently the car will stop.
There are several contributing factors to this heat reduction. One of the most common sources of heat is from the gases produced by the bonding agents of the brake pad burning off. Under severe braking, this can actually produce a boundary layer of gas that pushes the pad away from the rotor, which can lead to excessive brake fade. The cross-drilled holes or slots in a rotor provide an escape path for these gasses (de-gassing or out-gassing are common terms), and allow the pad to stay in contact with the rotor. As well as de-gassing, cross drilling or slotting will provide better wet weather braking as water is swept through the holes, or down the slots.
A vented rotor can be viewed as an air fan. When in motion, the vents draw air from the center of the rotor outward. This air flow, over an increased internal surface area, effectively dissipates rotor heat. Cross drilling adds to this air flow, as well as providing additional rotor surface cooling.
I would like you to explain how the following car/motorcycle manufactures are putting inferior brake systems on the road:
Mercedes Benz
Chevrolet
Ferrari
Porsche
Harley Davidson
FORD
Saleen
Kawasaki
Yamaha
Buell
Honda
Rolls Royce
Aston Martin
BMW
Bugatti
Lamborghini
Lotus
Vector
I could go on, but I am sure you see my point. BTW drilling and slotting are not for cooling, it is for pulling the gasses created by braking away from the surface where it will cause brake fade.
May 20, 2004 | 08:34 PM
#9
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right after you explain to me why people that do this for a living are wrong. And right after you tell my why wilwood and baer would lie.
<---worked for TRW for a year and ALL we did was make brakes and calipers.
They do it because it looks cool. the same reason they have spoilers, all those air inlets, cool looking wheels when they could be lighter ect. I said that above.
"OMG IT MUST BE THE BEST THING! FERRARI DOES IT!"
Go ask autocrossers and road racers why they dont use cross drilled rotors.
Pads today dont outgas. If you are racing, or street driving, choose the right pad and you wont have outgassing.
Id go on, but you wouldn't get the point. Its like pointing and screaming "look at that" to a blind man.
The problem is that I cant argue with you. I have a fundamental handicap that requires me to think logically and explain things reasonably. Someone selling it does not consititute a logical or persuasive argument.
<---worked for TRW for a year and ALL we did was make brakes and calipers.
They do it because it looks cool. the same reason they have spoilers, all those air inlets, cool looking wheels when they could be lighter ect. I said that above.
"OMG IT MUST BE THE BEST THING! FERRARI DOES IT!"
Go ask autocrossers and road racers why they dont use cross drilled rotors.
Pads today dont outgas. If you are racing, or street driving, choose the right pad and you wont have outgassing.
Id go on, but you wouldn't get the point. Its like pointing and screaming "look at that" to a blind man.
The problem is that I cant argue with you. I have a fundamental handicap that requires me to think logically and explain things reasonably. Someone selling it does not consititute a logical or persuasive argument.
May 20, 2004 | 08:41 PM
#10
"right after you explain to me why people that do this for a living are wrong. And right after you tell my why wilwood and baer would lie"
Not calling them liers, sounds like an opinion to me.
"<---worked for TRW for a year and ALL we did was make brakes and calipers"
Worked in the performance industry 20 years
"OMG IT MUST BE THE BEST THING! FERRARI DOES IT!"
dont really care about what they are doing, just making a point that they would not do it if it did not provide something. That process cost money.
"Go ask autocrossers and road racers why they dont use cross drilled rotors"
Would be more than happy to do so, I know plenty that use them.
"Pads today dont outgas. If you are racing, or street driving, choose the right pad and you wont have outgassing"
BS you are mis-informed
"Id go on, but you wouldn't get the point. Its like pointing and screaming "look at that" to a blind man."
Not blind, just informed.
"The problem is that I cant argue with you. I have a fundamental handicap that requires me to think logically and explain things reasonably. Someone selling it does not consititute a logical or persuasive argument"
I could go on, but I feel I am wasting my time with your fundamental handicap.
Not calling them liers, sounds like an opinion to me.
"<---worked for TRW for a year and ALL we did was make brakes and calipers"
Worked in the performance industry 20 years
"OMG IT MUST BE THE BEST THING! FERRARI DOES IT!"
dont really care about what they are doing, just making a point that they would not do it if it did not provide something. That process cost money.
"Go ask autocrossers and road racers why they dont use cross drilled rotors"
Would be more than happy to do so, I know plenty that use them.
"Pads today dont outgas. If you are racing, or street driving, choose the right pad and you wont have outgassing"
BS you are mis-informed
"Id go on, but you wouldn't get the point. Its like pointing and screaming "look at that" to a blind man."
Not blind, just informed.
"The problem is that I cant argue with you. I have a fundamental handicap that requires me to think logically and explain things reasonably. Someone selling it does not consititute a logical or persuasive argument"
I could go on, but I feel I am wasting my time with your fundamental handicap.