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I don't expect you to get it. That ship has sailed.
Since you've already lost the surface area argument, let me debunk your mass argument as well.
A solid rotor has more mass to absorb heat, very good. That's nothing new. It also means that it takes LONGER to cool down. You want a quick lesson in thermal heat transfer, go look at intercoolers. A large, 4" thick heavy intercooler will make the intake air temperatures rise more slowly than a lighter one that is only 3". But it's the 3" that will cool down the fastest.
Rotors work the same way, except that the increased airflow from drilled over solid coupled with MORE surface area, not less as you've said, contribute to decreased heat.
There was an argument postulated by another clueless poster here... They said that designers design the cars, then the bean counters get involved and cut costs everywhere, and then the engineers get to have their say.
So tell me, which do you think is more expensive to make, a solid disc or a drilled one? Hmm, doesn't seem to make sense that an automaker would spend exponentially more money on drilled discs just for looks, when they're all trying to build cars as cheaply as they can.
IT'S NOT FOR LOOKS. No matter how many times you want to tell yourself it is, you'll still be wrong.
As an engineer myself, I'm flattered you think we solely dictate the design. Wanna know why the Corvette has bigger diameter wheels on the back than it does on the front? Because it will look out of proportion with the taller rear end. An engineer would have made them them the same size.
I hate to burst your bubble, but even high end exotics do things just for looks. More people buy cars based on appearance than actual race performance. Do think a convertible is really required for the racetrack? Corvette's chief engineer was once asked why he made a Z06 in s convertible. His response was that's what people will buy and pay more for. It's hard to argue you need a 21in performance wheel when NASCAR is running 200 mph on 15s.
Since when is a Porsche or Ferrari a low margin, high production car that requires cost cutting? It's not a Camry. Ferrari will gladly put $20k worth of brakes on their car and pass 100% of the cost onto their customer.
I'm up for entertaining a technical debate, but it would help if you didn't come off like an arrogant kid who works at autozone.
I don't expect you to get it. That ship has sailed.
Since you've already lost the surface area argument, let me debunk your mass argument as well.
A solid rotor has more mass to absorb heat, very good. That's nothing new. It also means that it takes LONGER to cool down. You want a quick lesson in thermal heat transfer, go look at intercoolers. A large, 4" thick heavy intercooler will make the intake air temperatures rise more slowly than a lighter one that is only 3". But it's the 3" that will cool down the fastest.
Rotors work the same way, except that the increased airflow from drilled over solid coupled with MORE surface area, not less as you've said
Increased airflow from what? The poor aerodynamics of s brake rotor?
Now turn your intercooler sideways (parallel to airflow) and get back with us.
May I muddy the waters further?.
Dimpled rotors, good or bad?
dimpled rotors are like slotted rotors. they offer a path for gases produced when brake pads out gas to go rather than sit between the rotor and the pad causing brake fade.
as for drilling rotors, and racing, it is very possible, since i have not read a rule book for nascar in some time, that the teams cannot use drilled and slotted rotors by rule. race series where they are legal though, the teams will often use them, especially in high heat situations, short tracks and tight road courses where the brakes are used hard regularly.
But simple math can prove that the surface area of a 1/8th inch hole drilled into a 1/4 inch thick rotor will have nearly 6 times the surface area.
You must have typed this before I had a chance to correct my blunder. Still stands that the drill hole area must be less than sidewall area. I think this is normally the case, but I don't know.
You must have typed this before I had a chance to correct my blunder. Still stands that the drill hole area must be less than sidewall area. I think this is normally the case, but I don't know.
It actually doesn't. Let's say we drill a 1/4" hole in a 1/4" thick rotor. The surface area lost from the brake surface is equal to 3.14 times r^2, or 3.14 x .125 x .125. Surface area is .0491 lost from the rotor face. That is all that is lost from the braking surface. Now, if we're talking total surface area lost to vent heat, we double that to account for the surface lost on the other side of the hole, and we get .0982.
Surface area of a cylinder is calculated by (2 x Pi x r x h), plus 2(pi x r^2). However, the second part would be the top and bottom circle, which are now gone from drilling, so we're left with just the first part of the calculation. 2 x 3.14 x .125 x .25 where .125 is again our radius and our rotor height is .25.
That equals a surface area on the inside of the drilled hole of .1963.
Divide that by .0982, and total surface area from drilling a 1/4" hole in a 1/4" thick rotor DOUBLES the surface area.
Now, this is an extreme example, that's much too large a hole for a 1/4" thick rotor, but as you can see, cross drilling leads to an increase in surface area. Using my previous example of a 1/8" hole in a 1/4" rotor, it comes out to being 4 times the surface area.
May I muddy the waters further?.
Dimpled rotors, good or bad?
They're the worst rotors you can buy. The dimples decrease the braking surface, and would only marginally increase surface area. You don't get the benefits of increase airflow since it's still a solid rotor basically. So no real additional cooling benefit, and less braking surface.
dimpled rotors are like slotted rotors. they offer a path for gases produced when brake pads out gas to go rather than sit between the rotor and the pad causing brake fade.
No. Unless you're using old compound asbestos pads, brake pads do not outgas anymore and haven't for a few decades. Read the braking tech links I posted.
Quote:
as for drilling rotors, and racing, it is very possible, since i have not read a rule book for nascar in some time, that the teams cannot use drilled and slotted rotors by rule. race series where they are legal though, the teams will often use them, especially in high heat situations, short tracks and tight road courses where the brakes are used hard regularly.
No. High heat situations are worse on drilled rotors due to the heat stress risers at the holes and they crack faster and can fail more spectacularly.
The only racers that still use drilled rotors are in classes where every ounce of unspring mass matters, like in motorcycle road racing and ultra light formula cars, and in those cases, they swap out the rotors after every event to prevent such failure. Note, Formula1, Indy, and NASCAR don't ban crossdrilling. They simply don't use it due to the points of failure. Trust me, if it worked better, F1 would have it.
It actually doesn't. Let's say we drill a 1/4" hole in a 1/4" thick rotor. The surface area lost from the brake surface is equal to 3.14 times r^2, or 3.14 x .125 x .125. Surface area is .0491 lost from the rotor face. That is all that is lost from the braking surface. Now, if we're talking total surface area lost to vent heat, we double that to account for the surface lost on the other side of the hole, and we get .0982.
Surface area of a cylinder is calculated by (2 x Pi x r x h), plus 2(pi x r^2). However, the second part would be the top and bottom circle, which are now gone from drilling, so we're left with just the first part of the calculation. 2 x 3.14 x .125 x .25 where .125 is again our radius and our rotor height is .25.
That equals a surface area on the inside of the drilled hole of .1963.
Divide that by .0982, and total surface area from drilling a 1/4" hole in a 1/4" thick rotor DOUBLES the surface area.
Now, this is an extreme example, that's much too large a hole for a 1/4" thick rotor, but as you can see, cross drilling leads to an increase in surface area. Using my previous example of a 1/8" hole in a 1/4" rotor, it comes out to being 4 times the surface area.
I think you misunderstood my statement because you are restating it: Area of the drill hole (pi*r^2) (*2 for both ends) must be less than the sidewall (cylinder wall) area (pi*d*h) in order for that to be true. As I said, i think normally it is the case that drilled rotors have more surface area than non drilled of the same type but I don't know enough about the multitude of aftermarket drilled rotor specs to say for certain.
They're the worst rotors you can buy. The dimples decrease the braking surface, and would only marginally increase surface area. You don't get the benefits of increase airflow since it's still a solid rotor basically. So no real additional cooling benefit, and less braking surface.
So returning to the slotted variety, the only difference between a dimpled rotor and a slotted is length of the depression.
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