Painted Brake Calipers = More Heat Retention?
 

I've been thinking of painting or powder-coating my brake calipers, but after further thought, I realized I would essentially be insulating the aluminum calipers and causing them to retain more heat that might otherwise be dissipated into the atmosphere. Am I correct in thinking this? Or would the affect be so small that it wouldn't matter?

I mean really if it would increase the heat retained in the calipers by any amount, I think I'd rather just clean and polish them a bit and not use paint.

PS. Are the rear calipers made of steel? I noticed mine had a little bit of rust on them, so I guess they aren't aluminum? Maybe I'll just paint the rear calipers to prevent corrosion...

Good question, get one of those craftsman temp probes and paint one but not the other and see, maybe we should start putting heat sinks or watercooling on our calipers?

Yep, your right about heat retention and paint. In fact the smoother the surface the more it retains heat so polishing will do about the same thing. Now, on the street, does it matter? Probably not. Racing is another issue, you WILL get them hot and every little bit of heat dissapation helps. If you are worried about it, get some ceramic heat backing plates from HRP World and keep the heat from getting into the caliper in the first place.






WoooHooo!!! 1000th post!

Heat
 

Flat black paint will give off heat. Bright colors like white retain heat and reflect it. Example: Paint the motor flat black / Paint the firewall white. Any school boy / girl should know this.

I think thats flipped, dark colors absorb light (heat)

what everyone says is pretty much on target, I think. I have painted mine red, easy to clean and see leaks or problems. I run hawk blues, regular break fluid and NO ducts, and have not even a hit of brake heat problems and I typically hammer the brakes harder than the next guy, only advantage my underpowered ride has. So, I highly doubt you will have any adverse effects.

And I second Patman07...light colors dissipate heat, dark absorb. Based on the heat of a car interior, black vrs white. Just my thought, correct me if I am wrong. Good luck!!!!

Light colors do not dissipate heat, they may reflect it, but they do not dissipate/radiate it.

Likewise, dark colors may absorb heat energy better, but this also has nothing to do with dissipation. Look at the number of heatsinks on electrical gear that are black.

The original poster did bring up a good question about painting or powdercoating calipers - it most likely does not improve heat dissipation and could certainly hurt it. A good clean surface is your best bet. A rough surface will most likely give better thermal transfer (to the surrounding air) than a polished one.

-bill

Alright well I think I will just clean them well when I rebuild them and that's it. Makes sense and saves some money anyway.

The second poster mentioned attaching heat sinks the caliper... seems like an interesting idea, only problem is there is generally not much room for that (at least not with my wheels) and it's probably more efficient to just use ceramic or titanium backing plates.

Thanks for the input guys.

If you are that concerned about heat retention you need to be looking at recirculating the brake fluid rather than the miniscule effects of the caliper coating.

I'm not THAT concerned with brake cooling at all. My thought is simply that since coating a brake caliper offers NO performance advantage at all, and coating it could potentially decrease performance (though I'm sure it's probably a negligible amount), then why coat it? The pros of coating don't really outweigh the potential cons.

I said heat sinks were an "interesting" idea, not a good idea. That's why I said using backing plates is a better idea.

BTW, what do you mean by "recirculating" the brake bluid? I've heard of water cooling the brakes but I haven't heard of recirculating the fluid (though there are a lot of things I haven't heard of!)

Exactly. Prolly explains why Mazda chose to paint the oil pan black..............

Paint your calipers and buy some titanium backing plates from gooroo and damian.
Aftermarket calipers are painted, so I going to guess that the performance loss is not much of an issue?

I must be a Girl.
 

There are a few paints that increase surface area to remove heat. If you use standard paints it will not help but hurt.

If I remember my physic class in high school it is dark colors that retain heat and bright reflex heat. Remember walking bear foot on a black ash fault road and jumping from one cool white line to the next as a kid. That sort of proves my point. Oh if you haven’t try it on a hot summer day then try it then you will understand.

Black will absorb and radiate heat better than other colours, but any time you have an interface of two materials, even if it's just 2 pieces of the same material (two halfs of the caliper for instance) it creates a resistance to conduction. If the heat can't conduct to the surface of the paint very easily it won't get dissipated as quickly. I'd leave them, just give them a good cleaning.

This thread is so nit picky, I love bullshitting about the most negligible(spelling?) things on forums.

Speaking of recirculating brake fluid, anybody done this for reduced fade/etc? Sounds like it could have some awesome potential, Brake fluid cooler?

I believe the colors dont really matter since the heat is being generated by friction not LIGHT. If you happen to have brakes that harness light energy please let me know. . . A white pot in an oven at 350 degrees is just as hot as the black one. If you rub to pieces of sandpaper together one set white the other black I bet the temperatures on both will be similar. Heat in braking systems is from friction not the sun. If you are worried about heat do what others say and just run some ducts and or those backing plates. I have no experience with the backing plates but the ducts seem to work well for most Racecars.

Colors
 

We're both right! It does both. Thats why the rad is flat black.

Just to clear this up... I think color does make a difference. Black is actually the absence of color - it looks black because it absorbs light instead of reflecting it. White and reflective surfaces reflect the most light. The colors behave the same way for radiated heat (same thing as light just in different wavelengths, mostly infrared, not in the visible spectrum).

Think of it this way: black allows heat radiation to pass through it. White reflects it, so the radiation does not pass through it as easily.

The caliper is heated mechanically through contact with the hot fluid and pistons. Here color doesn't really matter. But for the caliper to cool efficiently, it needs to transfer this heat to the surface of the caliper and radiate the heat into the air as infrared radiation. I think a bright or reflective coating on the surface of the caliper would prevent this heat from radiating to the air as well. Black would allow heat to pass through easier.

Of course choice of coating material matters much, much more. Coating a caliper with ceramic would probably not be a good idea. I was actually more concerned with the insulating properties of the material used in the paint rather than the color. Don't the high-temp caliper paints have ceramic in them?

If I were going to paint them, I'd paint them black, but I think I will just leave them as is. I'll probably powder coat the rear calipers for corrosion resistance, but they don't get anywhere near as hot as the fronts anyway.

I believe most of the engine/hi-temp paints to have ceramic in them. I painted an extra set of calipers a while go using some black hi-temp engine paint. Honestly, the stuff is so thin I can't imagine it making that much difference. IMO if you are running that close to the edge of your brakes, it might be time to look at ways to reduce the heat transfer (like different backing plates mentioned earlier).

http://www.2dperformance.com/shims.asp

However, if it's a true competition race car, you'll have to deal with what the specs allow.

So, by all this reasoning, you should paint your radiator black to improve it's heat transfer????

AARRRGGGGHHHH!!!!!

<*sigh*>
So much bad high-school physics, so little time...

-bill

RaceDriver7, black is actually ALL colors combined, white is the absence of color. I'll go along with everything else you said though. :)

Heat is transfered three ways, conduction, convection and radiation. Brakes are cooled all three ways. Conduction through contact with the rim, then the rim is cooled by convection(as is the brake rotor) and they radiate heat and get hot enough to glow red so there is probably some infrared radiation going on there.

The rougher the surface, the easier it will disipate heat. Paint fills in all the roughness.

With the ceramic brake pad backers you can cook the crap out of your pads and not worry about heat in the caliper and fluid.

Noooooo... A third grader might think this because you may get "black" if you mix a bunch of different colored paint together, but technically black is the absense of color and white is all colors together. It all comes down to light. White light has every color in the visible spectrum in it. Black is obviously the absense of light. Surfaces appear black because they disperse or absorb light. If you look this up you will see that it is correct. Surfaces appear white because they reflect all light. That's why if you shine a blue light on a white surface, it appears blue. It just reflects whatever light hits it.

Yes and no... of course it's better to not paint it at all! That's why I'm not going to paint my calipers. But the point is that if you ARE going to paint it, black would be the best color because it would radiate heat the best. This is somewhat relative because it depends on the material the paint is made of too - ie. ceramic black paint is probably much worse than white paint made from some other material that conducts heat well.

Damn, if you can believe wikipedia black is the absence of color. Thats what I get for listening to my art history major/artist wife! I guess the confusion is from how you mix to get black and what it ends up to be, "The perfect absorber of light". :bowdown:

No.

It will not.

Get it right.

-bill

Well thermodymamicists call the theoretical perfect ratiator a "black body" anything less than perfect (real) is a "grey body".

Don't make me go dig my old thermodynamics text out and explain why that phrase has nothing to do with paint color. Your should first consider your earlier statement:

and consider why is it wrong.

-b

Anyway, I really don't think the colour has much impact on cooling anyway, since radiation probably won't be the most prevelant method of heat transfer, and adding the paint will decrease the rate of conduction of heat to the surface through the extra thickness and thermal resistance of the paint, and through the contact resistance at the interface between the metal and the paint.

Think of this. What color was the oil pan on you rotary engine, when it left the plant? Black. Why did they paint it black? They painted it, to prevent rust. They painted it black, to help draw heat out the oil. Air flow under the car then cooled the surface of the pan, so the process could continue.

As long as the paint is in fact black in the infrared spectrum (it may be possible for it to be black in the visible spectrum and white in the infrared spectrum) it will absorb and emitt most infrared light whereas white will simply reflect most of it. I don't see why this is incorrect. I is consistent with everything I have ever read or learned on the subject. I never studied thermodynamics though, so perhaps you can enlighten us by explaining why it's wrong and back it up with data or facts.

Or maybe I should just say no, actually you're wrong, and that can be sufficient just like your post :rolleyes:

I agree though that most of the heat is being dissipated through convection and not radiation so it probably would hardly make any difference anyway. In that sense the material selection (how well it conducts heat) is probably much more important. How did we even get on the subject of color?

If only you had stopped there, but nooooo.
Black paint (or any other color for that matter) on the outside of the oil pan does not help (nor hinder, nor affect in any way) the temp of the oil within.
In fact, the oil pan is not considered a part of the oil cooling system at all...if it were it would be finned (to increase surface area) and more care would have been taken to duct fresh air around it.
This is true of calipers as well.
*From the Wilwood website...*
"A durable black anodized finish is standard on most models, with some available in a polished finish for show car applications."
Note that no claim as to temp reduction/optimization is made, only that the finish is "durable". This follows several paragraphs detailing the steps taken to deal with heat issues- special seals/isolator pads/internal pathway optimization/ect....you'd think that the exterior finish would be listed as well if they could support the claim, but they can't so the finish is advertised as "durable" only.
Go ahead and paint your calipers any color you like, or leave them bare...ultimately it won't make a damn bit of difference.

It's interesting to note however that they anodize the caliper, not powder coat it or cover it with a layer of ceramic paint. Anyone know if any of the other aftermarket brake companies actually paint or coat their calipers in some way other than anodization?

Many aftermarket calipers are powder coated. As has been stated, the trick is to keep the heat out of the caliper in the first place. The heat that does get to the caliper will be sinked out to the spindle much faster then to the air.

Paul

this is rather amusing... i dont think it really makes a difference what color they are or if they are even painted

I dont think its really worth worrying about on a street car =P

color has no bearing on heat caused by friction. Brembo,endless, Wilwood, Project Mu all paint their calipers.

Here are my rz calipers with a fresh coat of epoxy paint for all the engineers here! :D

We're not arguing about colour affecting heat caused by friction, we're arguing about the rates of heat dissipation through radiation being affected by the colour.

and you actually think the color of an object, where light is not invloved, is really going to effect its ability to dissipate heat? :rlaugh:

also... I've never seen a 'high temp paint' that was rated at over 500 degrees... if you're going to be using your brakes to the point where you might be worried about heat dissipation this seriously, the temp of your brakes is going to be much higher than 500 degrees.... at which the paint will burn off, completely killing its 'ability to improve the heat disipation' of the object it is on.
so maybe with some sort of powder coating or anodizing or something... ? I don't know anything about those.... but even so, if color made even the slightest bit of difference, don't you think aftermarket brake companies would all paint their calipers the same color in order to improve their heat dissipation abilities?

how did this thread seriously last 3 pages on topic? :molepoke:

If all performance companies cared about was performance, then why do you get cross drilled rotors on countless performance cars (just one example)?

I don't think it makes that much difference, but there may be some. It'll probably matter more on what kind of coating you use, I'd immagine annodizing would be best, as it's just a layer of oxidized aluminum, not a seperate coating.

The point I was making is that he totally missed what was going on and called us morons for doing something that we weren't doing.

Actually, radiant heat is just electromagnetic radiation (i.e. light) at a slightly lower wavelength. So light is involved (or more accurately, em radiation is involved and therefore has exactly the same properties as light). Colour does have an impact on absorption and radiation of heat (and light), but the effect on a brake caliper is miniscule in proportion to convective cooling and is insignificant. Otherwise, Porsche wouldn't paint its race calipers red.

thread is confusing because people are getting mixed up between the two:

1)are we talking about the calipers radiating (SP) off its heat
or
2)the caliper absorbing heat

first off, if anyone's post here mentions they want to make the caliper absorb less heat, this really isnt possible, I dont know how hot the temerpatures get, but im sure its hot enough to reach the point where it will allow itself through whatever coating you have on your calipers. Heat is energy, it cannot just dissapear, it doesnt have many places to go, and it will choose the more eaiser conductor of whatever your calipers are made of over the air.

secondly, putting a coating on your calipers will increase the complete area of it, in result, the heat should dissapate at a lower concentration throughout the caliper,

this isnt the only variable:

also, putting a coat as I said increases total area, in result the heat will have to travel more distance to completely get off the caliper, in result, caliper retains heat longer

another variable

if caliper is larger once again the whole heatsink theory does apply, heat will be on the caliper longer, but, will not be as hot near the pads because the heat is no longer concentrated...

I can sit here and think of a hundred more variables, its all about plyaing a balancing game, which requires extensive experiments and data. We will NOT be able to find that unless we have thousands of dollars of equipment and shitloads of spare time, so if anyone wants to test this, with every single possibility, please do so, lol.

If it were as simple as painting a caliper a color to get more performance everyone would be doing it, and trust me, someone has thought of it before, with the population massively expading every year, its harder and harder to make new performance aiding discoveries, or more commonly, like in this case, just too damn time consuming and COSTLY.

was reading through and waiting for someone to bring this up. Simply put:

Color only effects thermal energy transfers from light (ie: sun), not thermal energy transfers via friction (ie: calipers and pads).

didnt have the time to read through the rest of the thread...

Heck, even AutoZone carries High Temp Paint rated to 1200F (look up the Dupi-Color brand).

It's okay to disagree and argue, but please no trash talking eachother. Thanks.

maybe me meant celcius? did a conversion, works out to 932F, pretty close...

Paint the calipers black as they will radiate more heat so to speak. The difference will be negligible. Ducting fresh air to the brakes will provide a greater benefit than painting the calipers but every little bit helps.

You guys are forgetting thet the paint will also act as an insulator, both by it's own thermal resistance and by the thermal contact resistance. I strongly feel that any possible small gains from better radiation will be more than offset by the increased resistance slowing conduction to the surface, slowing convection.

http://en.wikipedia.org/wiki/Thermal...ct_conductance

I can't imagine it makes much defference either way. If you went and powdercoated or painted your downpipe, regardless of color, would it significantly affect underhood temps? I doubt it unless it was a thermal coating of some kind.

god this is stupid... how can you still be seriously discussing this?

next its going to be, "what color and how many coats of paint should I put on my engine block to get the best cooling?"

its fucking paint, on things that get well over 1k degrees (brakes)... its not going to make the 'slightest' be of difference, whether you're talking about color, or insulation.