28plymouthman Posted May 10, 2018 Share Posted May 10, 2018 I sent my brake drums out to be powder coated. 1928 Plymouth with hydraulic brakes. They powder coated the back sides also. Is this car going to stop or should I grind the powder coating off the braking surface of the drum. The car doesn't go very fast. About 40 average. Are the shoes going to cake up or is the car not going to stop because the drums are slick. Any replies are appreciated. Thanks Link to comment Share on other sites More sharing options...
PONTIAC1953 Posted May 10, 2018 Share Posted May 10, 2018 if they powder coated the drums where the brake shoes ride the drum, you're not going to be able to stop. Link to comment Share on other sites More sharing options...
keiser31 Posted May 10, 2018 Share Posted May 10, 2018 (edited) 41 minutes ago, pontiac1953 said: if they powder coated the drums where the brake shoes ride the drum, you're not going to be able to stop. My honey says to grind or replace. I agree with her. Edited May 10, 2018 by keiser31 (see edit history) Link to comment Share on other sites More sharing options...
Rusty_OToole Posted May 10, 2018 Share Posted May 10, 2018 See if you can find an old time brake shop that can turn the drums. Have them take off the minimum to clean up the drums even if it leaves a few scratches. New drums are getting hard to find, you want to get as much wear out of them as you can. 1 Link to comment Share on other sites More sharing options...
c49er Posted May 10, 2018 Share Posted May 10, 2018 The shoes need to rub against raw metal! Link to comment Share on other sites More sharing options...
1937hd45 Posted May 10, 2018 Share Posted May 10, 2018 There is a first time for everything both good and bad. Bob Link to comment Share on other sites More sharing options...
Real Steel Posted May 10, 2018 Share Posted May 10, 2018 (edited) Your brake shoes will now be sliding smoothly on plastic. Even if you manage to get the plastic off the inner friction surfaces, the rest of the plastic coating will probably turn into a gooey mess. Your powder coat guy should be held criminally responsible for doing something so...'unusual'. Edited May 10, 2018 by Real Steel (see edit history) 1 1 Link to comment Share on other sites More sharing options...
Spinneyhill Posted May 10, 2018 Share Posted May 10, 2018 (edited) 2 hours ago, Real Steel said: the rest of the plastic coating will probably turn into a gooey mess. eh? I thought powder coating was basically paint solids applied with static electricity and baked on? Edited May 10, 2018 by Spinneyhill (see edit history) Link to comment Share on other sites More sharing options...
28plymouthman Posted May 10, 2018 Author Share Posted May 10, 2018 Thanks for all the replies. Will have them turned to get back to raw metal. 1 Link to comment Share on other sites More sharing options...
R Walling Posted May 10, 2018 Share Posted May 10, 2018 52 minutes ago, Spinneyhill said: eh? I thought powder coating was basically paint solids applied with static electricity and baked on? The "paint solids" are plastic dust that fuse together with heat. They will also smear with heat. Think slippery! Link to comment Share on other sites More sharing options...
Friartuck Posted May 10, 2018 Share Posted May 10, 2018 Powder coat is polyester powder that is melted on at 425 degrees. As the shoes make contact, the heat produced will melt the poly and get into the shoe and render it useless. Sand the contact area to get back to raw metal. Turning them also works. Link to comment Share on other sites More sharing options...
1937hd45 Posted May 10, 2018 Share Posted May 10, 2018 1 hour ago, 28plymouthman said: Thanks for all the replies. Will have them turned to get back to raw metal. Asking someone to ruin a brake machine doing something it isn't designed to do takes a set of stones. Bob Link to comment Share on other sites More sharing options...
Matt Harwood Posted May 10, 2018 Share Posted May 10, 2018 I doubt the thin layer of powdercoat scraped off the brake drum by a brake lathe will do any damage to the lathe. It's made to grind iron, for Pete's sake. The powdercoating will come off in little crumbs that can be vacuumed up. It won't gum up the works unless you get it hot enough to melt, which won't happen here. 6 Link to comment Share on other sites More sharing options...
Bloo Posted May 10, 2018 Share Posted May 10, 2018 Are these drums cast iron? If so, the brake lathe will probably do fine. Stamped sheetmetal drums, on the other hand, need to be ground. Link to comment Share on other sites More sharing options...
Luv2Wrench Posted May 10, 2018 Share Posted May 10, 2018 Is it OK to paint the outside of the drum with an epoxy primer? I'm using SPI two-part epoxy primer that is good to at least 500 degrees. Link to comment Share on other sites More sharing options...
poci1957 Posted May 10, 2018 Share Posted May 10, 2018 27 minutes ago, Luv2Wrench said: Is it OK to paint the outside of the drum with an epoxy primer? I'm using SPI two-part epoxy primer that is good to at least 500 degrees. That is how I did my Pontiac. I had a set power coated and was later informed that the power coating restricted heat dissipation and paint is better. 1 Link to comment Share on other sites More sharing options...
Rusty_OToole Posted May 10, 2018 Share Posted May 10, 2018 I painted mine with 2 coats of gloss black rust paint and never had a problem. They don't get that hot under normal circumstances. If you want something that is very durable, heat proof and dissipates heat well try black barbecue paint. 1 1 Link to comment Share on other sites More sharing options...
Bloo Posted May 10, 2018 Share Posted May 10, 2018 To dissipate heat, thinner and blacker is better. I like Rusty's barbecue paint idea. Link to comment Share on other sites More sharing options...
C Carl Posted May 10, 2018 Share Posted May 10, 2018 At the speeds you will be gently driving, you do not have to worry about heat dissipation at all. - CC 3 Link to comment Share on other sites More sharing options...
60FlatTop Posted May 10, 2018 Share Posted May 10, 2018 My Uncle Sam was a boss in the machine shop when they started building those '28 Plymouths. That new Hotchkiss rearend was a big deal. He had some trade magazine pictures of him standing by an axle on a table. He told me the first of the cars were built in circus tents. Chrysler only had enough money for production equipment and had to wait for a building. The machines were set and the tents were rented to protect them. That story was told about 30 years after it happened. #0 years seemed like a lot longer back then. Bernie Link to comment Share on other sites More sharing options...
Frank DuVal Posted May 11, 2018 Share Posted May 11, 2018 So, poci, did you remove the power coating or continue to use them with no issues? This paint vs powder coating is interesting, as they are both methods to get solids onto a surface, in order to protect or decorate a surface. One does it by dissolving the solids in a solvent and the other by getting the solids onto the surface (static electricity makes it stick while still a powder) and then baking it to make it flow. [Hmm, almost like the OEM reflow paint systems]. There is paint with polyester solids, and there are solids of polyester in powder coating. So why do people make such a big "it is different!" deal out of this? Link to comment Share on other sites More sharing options...
Rusty_OToole Posted May 11, 2018 Share Posted May 11, 2018 The guy who did the powder coating could have wiped the braking surface with a rag in a few seconds. I guess he didn't know it mattered. Something to keep in mind if you are having brake drums powder coated. Link to comment Share on other sites More sharing options...
Akstraw Posted May 11, 2018 Share Posted May 11, 2018 I don't think that you will have any problems with the powder coating on the outside of the drums, but agree that you should have a bare metal inner friction surface. I don't think it would be safe to drive with the inner surface coated. Link to comment Share on other sites More sharing options...
poci1957 Posted May 11, 2018 Share Posted May 11, 2018 13 hours ago, Frank DuVal said: So, poci, did you remove the power coating or continue to use them with no issues? I used them as is until the brakes were chattering badly and needed work (NOTE these were the famous 8 lug aluminum drums as seen in the photo. I am smiling since I had an extra set to replace the originals). The drums were slightly warped with hot spots and the linings overheated even though I had not driven the car hard or fast. This could be partially from the powder coat and partially from the finicky nature of these drums but either way a noted 8 lug rebuilder told me the powder coat restricts heat dissipation and my car seems to have had a problem in that area, Todd C. 1 Link to comment Share on other sites More sharing options...
lump Posted May 11, 2018 Share Posted May 11, 2018 I grew up in the AACA, Southern Ohio Chapter, but fell in love with muscle cars while I was in high school. I became a serious street racer in the early 1970's (I know...shame on me!) Anyway, I recall LOTS of us street punks painting our brake drums different colors, so they would look "cool" where you could see them between spokes of our mag wheels. I also recall lots of different brake specialists telling me that this was a bad idea, because the drums would not dissipate heat as well with paint on them. True, we did ruin a lot of brake drums, but I suspect this had a lot more to do with the constant abuse we put our cars through back then (power-braking, burnouts, panic stops when we spied a cop, etc, etc.) I would never suggest powder coating brake drums, or any other car part which is subject to a great deal of heat. Just my opinion. Link to comment Share on other sites More sharing options...
mike6024 Posted May 11, 2018 Share Posted May 11, 2018 There are 3 methods of heat transfer: conduction, convection and radiation Supposedly : Dark, matt surfaces are good absorbers and emitters of infrared radiation. Light, shiny surfaces are poor absorbers and emitters of infrared radiation. An example of this is the silvering inside a vacuum flask. You may have noticed that some roof sheathing comes with foil on it. This has an insulating effect, but it does not impede heat conduction like fiberglass insulation, but rather impedes radiation,. Would powder coating impede heat transfer? I doubt it. That is compared to paint, why would black powder coat be worse than black paint? It could affect either conduction or radiation, but how or why it would be significantly different than paint is not clear. Link to comment Share on other sites More sharing options...
Spinneyhill Posted May 12, 2018 Share Posted May 12, 2018 (edited) Brake drums are probably cooled by convection mainly, as they move along the road. I am not sure paint makes any difference to that. It is about conductance to the surface then convection off it into the moving fluid (air). The Stefan-Boltzmann Law is the one about dark and light coloured surfaces absorbing and emitting heat at different rates. Edited May 12, 2018 by Spinneyhill (see edit history) Link to comment Share on other sites More sharing options...
FJD Posted May 12, 2018 Share Posted May 12, 2018 One item overlooked is that when the drums are minus the powder coating, and turned down, all of the drums can be turned to the same safe diameter. which in reality they should be any way. Some powder coating also provides a great primer coat for painting, which can be touched up which difficult to touch up powder coating. good luck Link to comment Share on other sites More sharing options...
ArticiferTom Posted May 12, 2018 Share Posted May 12, 2018 May want to simply sand blast surface then can be ground true with out damaging stones . My drums are factory painted yellow and heat never bothered them . 1 Link to comment Share on other sites More sharing options...
FJD Posted May 12, 2018 Share Posted May 12, 2018 When they are off and at the machine shot being brought to the correct or matching diameter is an excellent time to replace bearings and races. That is how I had mine done for a 1940-120. Good luck Link to comment Share on other sites More sharing options...
Mark Shaw Posted May 13, 2018 Share Posted May 13, 2018 On 5/10/2018 at 12:35 PM, C Carl said: At the speeds you will be gently driving, you do not have to worry about heat dissipation at all. - CC Carl, I would agree....; until some numb nuts tour leader sends everyone down a steep hill with a stop sign at the bottom! Link to comment Share on other sites More sharing options...
Ben Bruce aka First Born Posted May 13, 2018 Share Posted May 13, 2018 1 hour ago, Mark Shaw said: Carl, I would agree....; until some numb nuts tour leader sends everyone down a steep hill with a stop sign at the bottom! Mark, that is what first gear is for!? Ben 1 Link to comment Share on other sites More sharing options...
Real Steel Posted May 13, 2018 Share Posted May 13, 2018 To remove power coat, apply an oven cleaner, like Easy-Off or something similar. Let it sit, then rub with a coarse pad. Link to comment Share on other sites More sharing options...
sligermachine Posted May 16, 2018 Share Posted May 16, 2018 I would be afraid of the plastic egg shell - covering . Catching on fire after I came down a long grade and starting a firer under my car . I weld on all kinds of stuff at my machine shop and the powder coating burns good once good and hot.--kyle 1 Link to comment Share on other sites More sharing options...
JWLawrence Posted May 16, 2018 Share Posted May 16, 2018 On 5/10/2018 at 12:40 PM, Bloo said: To dissipate heat, thinner and blacker is better. I like Rusty's barbecue paint idea. Agree, thinner is better. Color does not matter where the sun does not shine. JWL Link to comment Share on other sites More sharing options...
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