Does caliper color affect heat dissipation?

[chrisp]

I am refreshing my SC calipers and am trying to decide between silver and black. I recall reading somewhere that black dissipates heat better than lighter colors. Also, reading the 1200 degree rattle can it says it has ceramic in it. By refinishing with this paint am I just insulating them from the outside world...and thus keeping the heat inside? FYI, this is a G-class race car and thus has less than ideal brake sizing...so I don't want to do anything that will make them less effective.

[NY65912]

From what I have been told, do not put any type of paint/coating on your calipers. I was thinking or painting my set of 930 calipers that are going on to the SC and experts said not to, for heat dissapation.

But then again, I've seen 100's on cars with painted calipers on the street, no problem there. I would not do it.

Just MHO

[Nine9six]

Are you racing in such a competitive class. that the infinitesimal difference between painted and non-painted calipers would make a difference?

[randywebb]

No - don't worry about it. Duct air, get bigger rotors, etc.

[Brother]

The rotor is the main heat sink.

All the sweet Big Reds and new Porsche Yellows are painted.

[chrisp]

Thanks for the replies. The point is that in G-class the brakes stay stock and there's no option to upgrade rotors, calipers, etc. SC brakes get pretty hot and, for example, there's little chance you'll have effective braking under race conditions without ducting. So, anything I can do to help them cool is the point here. I know big reds are red and modern performance cars have colored calipers. Those are designed with that in mind and I would say that modern brakes have a much bigger margin built in than brakes in 1983. I'll search for some supporting info that's based in science.

[Bill Verburg]

There is a small difference in emissivity between white paint(worst) and black paint(best), unpainted would be slightly better than white. The difference is so small as to be not worth worrying about. You need lots of convective cooling and large thermal mass to keep them meaningfully cool.

[randywebb]

try Kreith or Kalekar and Desmond's texts on heat transfer.

Trust me - the color is not going to matter -- I used to give people PhDs in this.

The math is too complicated for a text based communication.

[chrisp]

Thanks.

[island911]

Originally posted by Bill Verburg
There is a small difference in emissivity between white paint(worst) and black paint(best), unpainted would be slightly better than white. The difference is so small as to be not worth worrying about. You need lots of convective cooling and large thermal mass to keep them meaningfully cool.

FWIW, most white paints are actually not the worst. (one of those counter-intuitive things . .. IIRC titainium dioxide is "black" for much of the spectrum, making many whites close to many blacks. An example of this would be white road stripes that get frosted faster than the black asphalt. -- please correct me if I'm wrong on this.

[aigel]

Plain aluminum and paint emissivities may be similar, but that does not cover the entire situation here. You have to take into account how the heat gets from the Al caliper to the TOP of the painted surface. I doubt that thermal conductivity of paint is anywhere close to that of aluminum, unless the paint is designed for it.

There is no value added by painting SC calipers. Even for the street it is silly. There is better things to do with your time and hard earned.

George

[austin552]

To a degree

[randywebb]

Metallic paints will have lower emissivity. The texts listed above give some data. Many think that metal will have very low emissivity - but that only holds true while it stays polished... once the sruface oxidizes, e will again tend towards 1.

And remember, the abs. temperatures are going to be raised to the 4th power...

But this is all far distant from his question.

Someday, however, I will paint my calipers red, just for the bling effect.