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Triumph TR6 - Painting Brake Drums

I just received advice from my across the street neighbor, who has restored many cars that I should not paint the brake drums because to do so reduces the heat dissipation attributes of the cast iron. Comments from those who know...??? If not painted, then how do you protect from rusting, which they do in a big hurry!@!
Doug Baker

I would bet my left nut (5/16 x 24 NF) that the colour black will disipate heat faster than rusty cast iron.
I'm not an expert, just speaking from my own observations. I've got lots of rusty iron in my garage, maybe this weekend I'll pull out 2 things the same clean and paint one of them, shove them in the oven for a hour and take note which one cools faster.
Should be interesting. I painted my rear brake drums high heat gloss black about four years ago. They still look good and I have never noticed brake fade.
Christopher T.

I also painted mine 4yrs ago...brakes are fine..if there is any problem it would be so slight we would never notice unless you have NASA monitor the heat loss rate.
Charlie B.

I doubt there is much of a difference. The temperature of the drums does not get hot enough to make radiation heat loss a significant contributor to cooling. The thickness of the paint film will add resistance to conduction of heat to the surface where it's convected away, but it's not going to amount to much. Paint those suckers.

Brent B

It would make more difference if we were talking about aluminum parts and anodize finish vs. paint, but for the cast iron boat anchors used as brake drums on these cars the difference would be neglible. Paint 'em

Well done and done. The left one has been POR 15'ed and the right is clean and scheduled!! Thanks to all for the comments. It's refreshing to have great friends lift one out of the weeds occasionally!!
Doug Baker

Doug- No PC??

Hey Don,
After POR'ing the drive shaft, the stuff is so much easier than powder coating and probably just as effective in corrosion protection, plus masking the braking and hub surfaces would have been an challenge even though I have the fiberglass tape, PW for the drums, although Riedel supposedly did PC his!!
Doug Baker

POR 15 is great stuff! My whole frame is now coated with it. The hardest part is cleaning all the old dirt and grease off. Pretty much everything I could conveniently get at to clean underneath is now a nice POR black.

JL Bryan

I'm with Steve - paint the brake drums with high heat paint from Eastwood or VHT. You will never notice any brake fade seat of the pants - these things are like tractors - not exactly a high performance braking system!

John Parfitt
73 5-Speed.
John Parfitt

I'm not so sure that POR 15 is something I would want to use on the brake drums. High temp paint was what I had in mind. There are a couple of reasons why I am not in the POR mindset for this application. First is that the coating thickness will be greater than with the high temp paint. The other is that POR 15 is not UV stable. If you are running wire wheels or something along the lines of Panasports, they will be exposed to UV, meaning a topcoat of a different paint over the POR 15 would be in order.

Steve, thanks. I had already decided to strip the POR (no small task, BTW) and start over with a thinner High Temp paint. I have an order ready for Eastwood, so I'll include some paint. You mentioned Anodized Aluminum. Is the intake manifold iron or aluminum? It's heavy but then the carbs are still attached, but it appears cast aluminum. Regardless, would you recommend the same HT paint for it as the brake drums (different color, of course) and the exhaust manifold as well (it's clearly iron)?
Doug Baker

Intake manifold is cast aluminum, the inserts threaded into it for the water lines should be cad plated steel as are the carb studs and the vacumm port for the servo. If you can find a high temp aluminum loaded paint, that would be the stuff to use if you wanted to paint it. I would advise not paiting it, just give it a good cleaning and then keep it that way to the greatest extent possible.

Eastwood has a finish specifically for cast iron manifolds. It is available in three colors, silver, black and of course, "cast iron." I have used the this before in "cast iron" and it seems to work rather well. Others on the board have mentioned using it as well with good results. Wire brush and blast that manifold, then when you thing you are done, go back and hit it some more. Then do a good solvent clean and follow up with some of the Eastwood stuff. A cheapy foam paint brush is the hot lick for application. Don't worry about the brush marks unless they are really gross, the stuff is largely self leveling.

I guess the other alternative would be to season a freshly prepared manifold like you would a new cast iron skillet. I can hear it now, "I'm going for a drive to season the exhaust manifold." Which at some point on the drive would be followed up with "Honest officer, the smoke is coming off my manifold where I'm trying to season it, I'm not cooking bacon under the hood/bonnet."

Regarding Chris' notion that black cools faster than rust, there is this equation relating how much an object radiates/emits (cools), and how much it reflects: emissivity = 1 - reflectivity. So if an object is black, black, black, black and doesn't reflect much light so 5%, then its emissivity is 95% and should cool better than something that is white, or higly reflective.

Of course, there are other factors like conduction of heat, you don't want to paint things too thick if you want it to cool.

And convection or blowing heat away from an object is probably the biggest factor.

I would be interested in Chris' results? But I think the bottom line is how hard do you drive your car, if you are stomping on your brakes a ton, then you will probably need new brakes drums before they rust apart.
Physics Geek :)


On the intake manifold I had very good luck with a wire wheel (fine) on the grinder and some isopropanol. I was able to get it back to its "natural" state, and then painted it with clear hi-temp paint to prevent oxidation. Looks really good with natural color tone.

Jim Vandenberg

What a wonderful idea. I'll give it some thought, although I think that I'll use the bead blaster to clean it up but a solvent to ensure squeaky clean is certainly a good idea. Thanks.

Now does anyone have any good ideas about how to get the damn water connections out of the intake manifold!! I've not used the BFH yet, but it's next in the tool box. Tried heat, but propane for a few minutes may not be enough to make a difference. Tried penetrant...Aerokroil for a month, no effect. I don't want to crack my manifold, but I think those connectors need to be replaced.
Doug Baker

I am about to take the drums off for painting, and so I am pleased that the black high heat paint I have for the job seems to be the way to go! I was planning to wire brush and paint the outside of the drums, but should I be doing the inside as well? Obviously not the actual friction surfaces, but the flat part?

Thanks in advance for any help and advice

I'm gonna paint everything that stays still long enough and doesn't run away!! The braking surface should be masked of course, or cleaned afterwards. I have little tolerance for rust or oil drippings. Guess I'll have to live with the one, but I can do something about the other:) The insides of my drums were just as rusty as the outside. Years ago, on my forever JEEP, I painted the drums with what today would approach POR. Never had an overheating problem and never had any rust.
Doug Baker

This thread was discussed between 31/10/2005 and 02/11/2005

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