Are Ceramic brakes worth it?
12-01-2014, 06:53 PM
#31
Racer
The idea that *some* people would pay $8,000 for PCCB where the primary driver (ha!) in that decision is the different color of the caliper (looks cool at Cars & Coffee!!!!) is embarrassing. I know Porsche is smart enough to make the caliper color different so that those "in the know" know that Hey I'm An $8,000 Option. But to get sucked in by that is the ultimate in being a poseur.
Yes, I get that most here buy them for other reasons. I am only referring to those who would pay $8000 primarily to show off the fact that they spent $8,000 on them.
Yes, I get that most here buy them for other reasons. I am only referring to those who would pay $8000 primarily to show off the fact that they spent $8,000 on them.
12-01-2014, 08:00 PM
#32
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I had them on my '06 C2S. I'm definitely getting them again for the dust reason. Stupid, maybe. But I hate cleaning the wheels on my 335 currently.
12-01-2014, 09:39 PM
#33
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The idea that *some* people would pay $8,000 for PCCB where the primary driver (ha!) in that decision is the different color of the caliper (looks cool at Cars & Coffee!!!!) is embarrassing. I know Porsche is smart enough to make the caliper color different so that those "in the know" know that Hey I'm An $8,000 Option. But to get sucked in by that is the ultimate in being a poseur.
Yes, I get that most here buy them for other reasons. I am only referring to those who would pay $8000 primarily to show off the fact that they spent $8,000 on them.
Yes, I get that most here buy them for other reasons. I am only referring to those who would pay $8000 primarily to show off the fact that they spent $8,000 on them.
12-01-2014, 09:58 PM
#34
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12-01-2014, 10:54 PM
#36
Given otherwise identical paint, darker colors will radiate (and absorb radiant) heat faster than lighter colors. So, yes, black calipers will radiate heat faster than red, yellow or white, but none of these colors will not shed heat. However, since brake cooling, for rotors and calipers, is largely a function of airflow (convection, not radiation), the color of the caliper doesn't significantly matter to how fast brakes will cool.
12-02-2014, 03:27 AM
#38
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12-02-2014, 03:50 AM
#39
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Given otherwise identical paint, darker colors will radiate (and absorb radiant) heat faster than lighter colors. So, yes, black calipers will radiate heat faster than red, yellow or white, but none of these colors will not shed heat. However, since brake cooling, for rotors and calipers, is largely a function of airflow (convection, not radiation), the color of the caliper doesn't significantly matter to how fast brakes will cool.
What this means is that, while you can achieve a cooling effect with no airflow (in a vacuum), based solely on the emissivity of the surface, you cannot achieve any convection cooling whatsoever if your surface has no emissivity. Introducing air flow does increase heat removal, as you say, through convection, but convection cannot exist if the surface has no emissivity, as there will be no heat "escaping" to be removed by the airflow. Therefore, optimum brake cooling requires optimum emissivity and airflow. Yes, more air flow will improve the convection cooling of any color, but it will improve the cooling of flat black more than it will improve the cooling of, say, gloss white, precisely because flat black's emissivity is superior. A given amount of air flow will remove more heat from a high-emissivity surface (flat black) than from a lower-emissivity surface (gloss white). So, brake cooling, for rotors and calipers, is a function of both convection and emission. You cannot have convection cooling of these components without heat emission...if the heat remains locked within the components (no emission), no amount of air flow will provide any convection cooling.
As you correctly point out, yellow, or even white calipers will also cool via convection. My point is, that they won't cool as well as they would if they were flat black instead. How much the difference matters on a mainly-road-driven 911 is, admittedly, questionable. Porsche (or anyone else) wouldn't sell red or yellow calipers if they weren't completely safe for road use, but when I read discussions here and on RennTech about people routinely and often replacing their brake fluid with this or that specific brand/type to achieve the highest possible boiling point for track use, I have to wonder why they don't re-coat their calipers in a thin coat of flat black paint (powder coating has low emissivity because it's so thick that it just acts as heat insulation, even in flat black) in addition to using those exotic fluids. They're bound to see some improvement, if only a little.
One everyday example that we cheaply/practically use to purposely achieve heat retention through low emissivity would be the chrome plating on your toaster, which is done more for heat retention than for cosmetic reasons...and the colorful, non-chrome toasters that you see are the equivalent of non-black brake calipers: cosmetic form over physical function.
12-02-2014, 03:16 PM
#40
Rennlist Member
I got PCCB (on my GT3s) because of two reasons:
1) significant reduction in unsprung weight (4x PCCB rotors vs steel)
2) better thermal performance characteristics
1) significant reduction in unsprung weight (4x PCCB rotors vs steel)
2) better thermal performance characteristics
12-02-2014, 03:54 PM
#41
Rennlist Member
Since "darker colors will radiate (and absorb radiant) heat faster than lighter colors", and since black is the darkest color, and since flat black has more surface area to emit heat than gloss black has...then flat black will emit more heat than any other color, whether there's air blowing on it or not. This property holds true whether in an atmosphere or in a complete vacuum. Just ask NASA. They regularly utilize the effect (black vs white) to evenly cool spacecraft. What this means is that, while you can achieve a cooling effect with no airflow (in a vacuum), based solely on the emissivity of the surface, you cannot achieve any convection cooling whatsoever if your surface has no emissivity. Introducing air flow does increase heat removal, as you say, through convection, but convection cannot exist if the surface has no emissivity, as there will be no heat "escaping" to be removed by the airflow. Therefore, optimum brake cooling requires optimum emissivity and airflow. Yes, more air flow will improve the convection cooling of any color, but it will improve the cooling of flat black more than it will improve the cooling of, say, gloss white, precisely because flat black's emissivity is superior. A given amount of air flow will remove more heat from a high-emissivity surface (flat black) than from a lower-emissivity surface (gloss white). So, brake cooling, for rotors and calipers, is a function of both convection and emission. You cannot have convection cooling of these components without heat emission...if the heat remains locked within the components (no emission), no amount of air flow will provide any convection cooling. As you correctly point out, yellow, or even white calipers will also cool via convection. My point is, that they won't cool as well as they would if they were flat black instead. How much the difference matters on a mainly-road-driven 911 is, admittedly, questionable. Porsche (or anyone else) wouldn't sell red or yellow calipers if they weren't completely safe for road use, but when I read discussions here and on RennTech about people routinely and often replacing their brake fluid with this or that specific brand/type to achieve the highest possible boiling point for track use, I have to wonder why they don't re-coat their calipers in a thin coat of flat black paint (powder coating has low emissivity because it's so thick that it just acts as heat insulation, even in flat black) in addition to using those exotic fluids. They're bound to see some improvement, if only a little. One everyday example that we cheaply/practically use to purposely achieve heat retention through low emissivity would be the chrome plating on your toaster, which is done more for heat retention than for cosmetic reasons...and the colorful, non-chrome toasters that you see are the equivalent of non-black brake calipers: cosmetic form over physical function.
Let's take another example... household radiators.... Yes they would be marginally more efficient if they were matt black... But so marginal that the vast majority are still sold and retained as gloss white... Go figure!
12-02-2014, 04:00 PM
#42
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12-02-2014, 04:57 PM
#43
While not necessarily relevant to the 991, some data points in the November 2014 Panorama Magazine:
https://www.pca.org/panorama/edition...-november-2014
https://www.pca.org/panorama/edition...-november-2014
They make a lot of sense on a road car. PCCB's are perfectly suited to the guy who will be doing almost all street driving, will not be pushing the car all that hard or all that often on the track, can change pads on schedule, and enjoys all the other benefits of PCCB. Autocross? Doesn't matter. Autox doesn't heat things up enough to matter either way. Cross em all you want. For this guy PCCB's will be the bomb, and this group covers a LOT of people, which is why so many who have them are happy.
PCCB's also make a lot of sense for the guy who has to win, has spent so much money on everything else it now makes sense to throw money at PCCB too- and still has money left to throw at PCCB's! In other words multi-millionaires and well-funded racing teams. Which is why so many hard core track guys complain (they can't afford to play with the big boys) and why so many professional teams run them.
I've been reading PCCB news and comments for years. When you hear someone complaining, almost always they are in the no-mans land between these two groups. If you're in there too, don't get them. Otherwise, odds are you'll love 'em.
PCCB's also make a lot of sense for the guy who has to win, has spent so much money on everything else it now makes sense to throw money at PCCB too- and still has money left to throw at PCCB's! In other words multi-millionaires and well-funded racing teams. Which is why so many hard core track guys complain (they can't afford to play with the big boys) and why so many professional teams run them.
I've been reading PCCB news and comments for years. When you hear someone complaining, almost always they are in the no-mans land between these two groups. If you're in there too, don't get them. Otherwise, odds are you'll love 'em.
12-02-2014, 05:02 PM
#44
The idea that *some* people would pay $8,000 for PCCB where the primary driver (ha!) in that decision is the different color of the caliper (looks cool at Cars & Coffee!!!!) is embarrassing. I know Porsche is smart enough to make the caliper color different so that those "in the know" know that Hey I'm An $8,000 Option. But to get sucked in by that is the ultimate in being a poseur.
Yes, I get that most here buy them for other reasons. I am only referring to those who would pay $8000 primarily to show off the fact that they spent $8,000 on them.
Yes, I get that most here buy them for other reasons. I am only referring to those who would pay $8000 primarily to show off the fact that they spent $8,000 on them.
