Track Tire and Caliper Data
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Hmmmm,
Tim,
Here is my $0.02.........
There are three basic components that make up your brakes. The rotors, the calipers and the pads. Let's ignore the trivial secondary components for a moment.
That said, lets look at each of these components individually with respect to cooling.
Rotors
The rotors are typically croiss drilled and internally vented with curved vanes. The rotor spins. Yes, it is shielded by the wheel barrel as well as the wheel well, but at least it spins and has venting.
Pads
You are running Pagid blacks so you have done what you can to create a "good" heat dissipating situation.
Calipers
The calipers just sit there. Other than the pads, they are the closest object to the heat generating interface (rotor surface/pad contact). If I was going to build an object to retain heat, I would build a big ol' caliper. I wouldn't put any cooling fins on it like an audio amplifier and I wouldn't supply air to it. Of course I am being facetious. LOL
My philosophy.........
The heat generated by the friction of the pads on the rotors is huge. A cooling airflow will do little to change the temperature by more than a few percent. Since the critical component is the brake fluid and the effects associated with boiling. Since each incremental area of the rotor only passes the pads with each revolution, it has "some" opportunity to cool as it spins with each wheel revolution. I would concentrate any cooling air on the caliper and not the rotor. It is the same philosopy as any heat sink that you see in electronics. Supply the cool air to the block that collects the heat.
That said, you already have the hoses in place. Change the delivery "register" to focus on cooling the caliper. I am going to look into this as well.
Of course, this is simply my opinion.
Tim,
Here is my $0.02.........
There are three basic components that make up your brakes. The rotors, the calipers and the pads. Let's ignore the trivial secondary components for a moment.
That said, lets look at each of these components individually with respect to cooling.
Rotors
The rotors are typically croiss drilled and internally vented with curved vanes. The rotor spins. Yes, it is shielded by the wheel barrel as well as the wheel well, but at least it spins and has venting.
Pads
You are running Pagid blacks so you have done what you can to create a "good" heat dissipating situation.
Calipers
The calipers just sit there. Other than the pads, they are the closest object to the heat generating interface (rotor surface/pad contact). If I was going to build an object to retain heat, I would build a big ol' caliper. I wouldn't put any cooling fins on it like an audio amplifier and I wouldn't supply air to it. Of course I am being facetious. LOL
My philosophy.........
The heat generated by the friction of the pads on the rotors is huge. A cooling airflow will do little to change the temperature by more than a few percent. Since the critical component is the brake fluid and the effects associated with boiling. Since each incremental area of the rotor only passes the pads with each revolution, it has "some" opportunity to cool as it spins with each wheel revolution. I would concentrate any cooling air on the caliper and not the rotor. It is the same philosopy as any heat sink that you see in electronics. Supply the cool air to the block that collects the heat.
That said, you already have the hoses in place. Change the delivery "register" to focus on cooling the caliper. I am going to look into this as well.
Of course, this is simply my opinion.
Last edited by KPV; May 11, 2005 at 08:03 AM.
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Rockitman, I think that is the weakest thing you've ever said on this forum. Shame on you! What you have just suggested is SLOW!, and typical PCA B.S. mantra. The fastest driver does two things, maximize g's along the ideal line. Braking early and gently is SLOW! and absolutely not what I will be doing. Dang, maybe you’re hung over or something.
Ken, I disagree with you as well, but not so strongly. I think we can all agree we are converting energy into heat. We need to dissipate the heat. This can be done in three ways, in order of importance, convection, conduction, and radiation.
Convection is best accomplished through moving more air. Since the rotor gets the hottest, the temperature difference is the greatest, and cooling the rotor with cool air is the highest priority. By going after the rotor, you have the highest surface area and the largest temperature difference and this dwarfs the cooling effect of blowing on one side of the caliper. Heat tranfser rate = -k A delta T. K is the heat transfer constant (the rotor’s is very high, the pad's is very low). A is the surface area, where the area inside the rotor is much larger than the back of the caliper. Delta T is the temperature difference and the T dif is much grater between the rotor and the cool air (maybe 800 degrees) than the caliper back and cool air (maybe 200 degrees). So, the heat transfer rate is superior by going into the curved vane rotor with cool, preferably ram air.
* Just as an interesting aside, for those people who slam huge rotors right that barely clear the wheel, there is no where for the air to flow out of the rotor and this really hurts brake cooling performance. You want an inch or more so that the air has room to exit from the rotor.
Conduction is the heat transferred from the rotor - into the pad - into the caliper – into the hat – into the hub – into the wheel – into the tire – etc. While a bigger caliper creates a bigger heat sink, it does not improve brake performance directly; it merely delays when the problem will occur. It also adds unsprung mass which is highly unfavorable.
Radiation is heat transferred from really hot stuff (sorry to be so technical). This is a fairly low important focus, and one we can’t do much with without hurting the much more important convection i.e. putting in a heat shield will dramatically hurt convection.
So COOLING AIR IS OF UTMOST IMPORTANCE and that is why every race car concentrates on getting air into the rotor.
Ken, I disagree with you as well, but not so strongly
. I think we can all agree we are converting energy into heat. We need to dissipate the heat. This can be done in three ways, in order of importance, convection, conduction, and radiation. Convection is best accomplished through moving more air. Since the rotor gets the hottest, the temperature difference is the greatest, and cooling the rotor with cool air is the highest priority. By going after the rotor, you have the highest surface area and the largest temperature difference and this dwarfs the cooling effect of blowing on one side of the caliper. Heat tranfser rate = -k A delta T. K is the heat transfer constant (the rotor’s is very high, the pad's is very low). A is the surface area, where the area inside the rotor is much larger than the back of the caliper. Delta T is the temperature difference and the T dif is much grater between the rotor and the cool air (maybe 800 degrees) than the caliper back and cool air (maybe 200 degrees). So, the heat transfer rate is superior by going into the curved vane rotor with cool, preferably ram air.
* Just as an interesting aside, for those people who slam huge rotors right that barely clear the wheel, there is no where for the air to flow out of the rotor and this really hurts brake cooling performance. You want an inch or more so that the air has room to exit from the rotor.
Conduction is the heat transferred from the rotor - into the pad - into the caliper – into the hat – into the hub – into the wheel – into the tire – etc. While a bigger caliper creates a bigger heat sink, it does not improve brake performance directly; it merely delays when the problem will occur. It also adds unsprung mass which is highly unfavorable.
Radiation is heat transferred from really hot stuff (sorry to be so technical). This is a fairly low important focus, and one we can’t do much with without hurting the much more important convection i.e. putting in a heat shield will dramatically hurt convection.
So COOLING AIR IS OF UTMOST IMPORTANCE and that is why every race car concentrates on getting air into the rotor.
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Originally posted by ColorChange
Rockitman, I think that is the weakest thing you've ever said on this forum. Shame on you! What you have just suggested is SLOW!, and typical PCA B.S. mantra. The fastest driver does two things, maximize g's along the ideal line. Braking early and gently is SLOW! and absolutely not what I will be doing. Dang, maybe you’re hung over or something.
Rockitman, I think that is the weakest thing you've ever said on this forum. Shame on you! What you have just suggested is SLOW!, and typical PCA B.S. mantra. The fastest driver does two things, maximize g's along the ideal line. Braking early and gently is SLOW! and absolutely not what I will be doing. Dang, maybe you’re hung over or something.
I had very little to drink last night...
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Originally posted by ColorChange
Rockitman, I think that is the weakest thing you've ever said on this forum. Shame on you! What you have just suggested is SLOW!, and typical PCA B.S. mantra. The fastest driver does two things, maximize g's along the ideal line. Braking early and gently is SLOW! and absolutely not what I will be doing. Dang, maybe you’re hung over or something.
Ken, I disagree with you as well, but not so strongly. I think we can all agree we are converting energy into heat. We need to dissipate the heat. This can be done in three ways, in order of importance, convection, conduction, and radiation.
Convection is best accomplished through moving more air. Since the rotor gets the hottest, the temperature difference is the greatest, and cooling the rotor with cool air is the highest priority. By going after the rotor, you have the highest surface area and the largest temperature difference and this dwarfs the cooling effect of blowing on one side of the caliper. Heat tranfser rate = -k A delta T. K is the heat transfer constant (the rotor’s is very high, the pad's is very low). A is the surface area, where the area inside the rotor is much larger than the back of the caliper. Delta T is the temperature difference and the T dif is much grater between the rotor and the cool air (maybe 800 degrees) than the caliper back and cool air (maybe 200 degrees). So, the heat transfer rate is superior by going into the curved vane rotor with cool, preferably ram air.
* Just as an interesting aside, for those people who slam huge rotors right that barely clear the wheel, there is no where for the air to flow out of the rotor and this really hurts brake cooling performance. You want an inch or more so that the air has room to exit from the rotor.
Conduction is the heat transferred from the rotor - into the pad - into the caliper – into the hat – into the hub – into the wheel – into the tire – etc. While a bigger caliper creates a bigger heat sink, it does not improve brake performance directly; it merely delays when the problem will occur. It also adds unsprung mass which is highly unfavorable.
Radiation is heat transferred from really hot stuff (sorry to be so technical). This is a fairly low important focus, and one we can’t do much with without hurting the much more important convection i.e. putting in a heat shield will dramatically hurt convection.
So COOLING AIR IS OF UTMOST IMPORTANCE and that is why every race car concentrates on getting air into the rotor.
Rockitman, I think that is the weakest thing you've ever said on this forum. Shame on you! What you have just suggested is SLOW!, and typical PCA B.S. mantra. The fastest driver does two things, maximize g's along the ideal line. Braking early and gently is SLOW! and absolutely not what I will be doing. Dang, maybe you’re hung over or something.
Ken, I disagree with you as well, but not so strongly
. I think we can all agree we are converting energy into heat. We need to dissipate the heat. This can be done in three ways, in order of importance, convection, conduction, and radiation. Convection is best accomplished through moving more air. Since the rotor gets the hottest, the temperature difference is the greatest, and cooling the rotor with cool air is the highest priority. By going after the rotor, you have the highest surface area and the largest temperature difference and this dwarfs the cooling effect of blowing on one side of the caliper. Heat tranfser rate = -k A delta T. K is the heat transfer constant (the rotor’s is very high, the pad's is very low). A is the surface area, where the area inside the rotor is much larger than the back of the caliper. Delta T is the temperature difference and the T dif is much grater between the rotor and the cool air (maybe 800 degrees) than the caliper back and cool air (maybe 200 degrees). So, the heat transfer rate is superior by going into the curved vane rotor with cool, preferably ram air.
* Just as an interesting aside, for those people who slam huge rotors right that barely clear the wheel, there is no where for the air to flow out of the rotor and this really hurts brake cooling performance. You want an inch or more so that the air has room to exit from the rotor.
Conduction is the heat transferred from the rotor - into the pad - into the caliper – into the hat – into the hub – into the wheel – into the tire – etc. While a bigger caliper creates a bigger heat sink, it does not improve brake performance directly; it merely delays when the problem will occur. It also adds unsprung mass which is highly unfavorable.
Radiation is heat transferred from really hot stuff (sorry to be so technical). This is a fairly low important focus, and one we can’t do much with without hurting the much more important convection i.e. putting in a heat shield will dramatically hurt convection.
So COOLING AIR IS OF UTMOST IMPORTANCE and that is why every race car concentrates on getting air into the rotor.
maybe you just need a CGT so you can experience "staggering" braking all day long
ps. i did that search for the brake expert i recommended yesterday. but, it's gonna be hard for you to PM yourself
Last edited by ben, lj; May 11, 2005 at 10:38 AM.
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Tim, just talked to a friend who runs Cup cars in IMSA, GA, etc. Told him about your problem. He immediately asked about your ride height. He said some people run Cup cars too low and that can cause brake overheating. He also said they're not boiling SRF. Granted, your car is overweight and a different animal, but given your setup my friend said "something's not right". Duh. Talk to a top race shop and get some input. Unless you just like to experiment and challenge yourself.
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Originally posted by ben, lj
maybe you just need a CGT so you can experience "staggering" braking all day long
maybe you just need a CGT so you can experience "staggering" braking all day long
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Rockit: The reason I dinged you so hard is that you’re normally so good. I do believe the fastest cup racers (pro’s) almost always DO use full ABS braking. And Yes, I have the data to prove it.
Secondly, I don’t believe typical cup cars would have a problem. At 1,000 less weight and almost 50% of the horsepower, their braking job is Way Less demanding than mine. Let’s look at some numbers and you’ll see what I mean.
Kinetic energy = ½ m v^2
So, for a typical hypothetical turn (50 mph), the Cup (2,500#) car approaches at 110 mph. My car (3,500#) approaches at 125 mph due to my 200 hp advantage.
Cup car = 4.50MM
My car = 9.84MM
My car requires more than 2x the braking than a typical cup car. As the speeds get higher, the difference becomes even greater.
Oak: Still keeping it as my daily driver.
Ben: Actually Ben, the weight is critical but the speed is squared so it is even more important. Now I can agree with you, that throughout a full day, your brakes offer staggering braking performance.
Super: I am at GT2 ride height specs and with my TA splitter up front, I am about 2.5” off the ground up front. As I just showed, there is nothing wrong with my car, just that it is too heavy, going too fast, with not enough brake cooling (right now). The cup cars have superior brake cooling as I previously pointed out. In fact, I may be using their brake air distributor (don’t know what the hell to call it).
I do believe the fastest cup racers (pro’s) almost always DO use full ABS braking. And Yes, I have the data to prove it. Secondly, I don’t believe typical cup cars would have a problem. At 1,000 less weight and almost 50% of the horsepower, their braking job is Way Less demanding than mine. Let’s look at some numbers and you’ll see what I mean.Kinetic energy = ½ m v^2
So, for a typical hypothetical turn (50 mph), the Cup (2,500#) car approaches at 110 mph. My car (3,500#) approaches at 125 mph due to my 200 hp advantage.
Cup car = 4.50MM
My car = 9.84MM
My car requires more than 2x the braking than a typical cup car. As the speeds get higher, the difference becomes even greater.
Oak: Still keeping it as my daily driver.
Ben: Actually Ben, the weight is critical but the speed is squared so it is even more important. Now I can agree with you, that throughout a full day, your brakes offer staggering braking performance.
Super: I am at GT2 ride height specs and with my TA splitter up front, I am about 2.5” off the ground up front. As I just showed, there is nothing wrong with my car, just that it is too heavy, going too fast, with not enough brake cooling (right now). The cup cars have superior brake cooling as I previously pointed out. In fact, I may be using their brake air distributor (don’t know what the hell to call it).
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Originally posted by ColorChange
Super: I am at GT2 ride height specs and with my TA splitter up front, I am about 2.5” off the ground up front. As I just showed, there is nothing wrong with my car, just that it is too heavy, going too fast, with not enough brake cooling (right now). The cup cars have superior brake cooling as I previously pointed out. In fact, I may be using their brake air distributor (don’t know what the hell to call it).
Super: I am at GT2 ride height specs and with my TA splitter up front, I am about 2.5” off the ground up front. As I just showed, there is nothing wrong with my car, just that it is too heavy, going too fast, with not enough brake cooling (right now). The cup cars have superior brake cooling as I previously pointed out. In fact, I may be using their brake air distributor (don’t know what the hell to call it).
What about running a wheel well venting test? Get a fender and liner off of one side of a salvaged TT (color unimportant), vent the liner and fender allowing evacuation of the hot air, and place sensors at both front corners to analyze temp variants with no other variables introduced. You're creating a hotter oven due to increased braking forces required as you've already demonstrated, so rather than just feed in more focused cooling air, vent the oven more effectively perhaps. Just thinking aloud. Dangerous to do so at times, I know.
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Tim,
That's a pretty good explanation for why the rotors should be cooled before any other part. FWIW, that's precisely what aftermarket kits aim at doing on my car (c5 z06) - getting the air directed into the middle of the rotor so it flows out through the vanes.
I'll be interested in seeing how much difference it would make for you. I have a similar problem with brake heat in my car especially at Road America and was hoping that some ducting will solve it/improve the situation.
Drew
That's a pretty good explanation for why the rotors should be cooled before any other part. FWIW, that's precisely what aftermarket kits aim at doing on my car (c5 z06) - getting the air directed into the middle of the rotor so it flows out through the vanes.
I'll be interested in seeing how much difference it would make for you. I have a similar problem with brake heat in my car especially at Road America and was hoping that some ducting will solve it/improve the situation.
Drew
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Ben, yes, you could be right. The better solution, and a fairly simple one, is to pull the lights. you then have high volume (4" line probably) super high pressure air. If what I have now doesn't work, that is what i will do next. I will have pics tomorrow.
Drew, yep!
Drew, yep!