Pagoda SL Group
W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: DB280SL on November 11, 2010, 17:02:01
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I am in the process of rebuilding all four calipers on my 1967 250SL. I read on another forum that ATE calipers were finished in gold cad, seen some pictures that look like silver cad, and been told by a well known restoration shop that rebuilds calipers that they apply the "correct factory finish"..... baked cast colored epoxy. I'm confused! Does anyone know the correct original finish on ATE calipers? I've done the "unthinkable" and split the calipers so can go with cad if it is the correct way to go.
Thanks
Darrell
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Darrell,
I don't believe there was any finish on the calipers at all. I believe they were raw cast iron.
You can keep them reasonable nice looking by use of Calyx Manifold Dressing, or have them painted or coated in a color to match raw cast iron. I've never seen anything but that on them.
But, I could be very wrong. Maybe others will check in here.
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Hi michael
Pretty sure they were cad plated, at least on my '68. Took mine apart 20 years ago and they were not rusty. Polished up nicely with a wire brush and did seem to have some yellow zinc residues on them, so i got them replated.....
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Here is a photo of Bob Possel's 280SL. I believe he had started a discussion whether to CAD plate or not.
Perhaps Bob can chime in.
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the bolts securing the caliper halves together were DEFINITELY NOT zinc plated, but phosphatized. Nor are the mounting bolts.
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Correct me if i am wrong but the torque link bolt is fitted the wrong way,the bolt head should be on the top.
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As not to veer too far from Darrell's thread; why can't you separate the ATE calipers? I seem to have read this in the BBB but can't find a thread as to why.
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You can separate the halves, it's just not recommended for safety reasons.
I've had to separate many (on other Mercs) in order that they can be removed when the retainer nut in the brake back plate detaches. I've never had any problems once they were reassembled.
Cad (yellow passivate) plating looks nice but doesn't last very long on anything but a show car.
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this has been discussed in other threads...they CAN be split, and easily so, but, for safety reasons noone endorses this. I split mine 20 years ago. and since i am just now putting my car back together I decided I would find ut what i could to use mine since they were in great shape. The internal o-rings are special o-rings, but they are available, just not from the normal sources...think UNIMOG.
I spoke with representatives at ATE when I first investigated, and while they can't officially help, they did indicate that they "probably" have a stash of bolts that would be available. Didn't have to go that route tho
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I continued to search the internet and came across a Porsche site, pmbperformance.com, that gave pretty detailed instructions on how to rebuild Porsche ATE calipers. According to this site the calipers were finished with yellow zinc. I've had the bolts re plated with black phosphate and have the calipers at the platers for yellow zinc. I'll post pictures of the finished product.
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... Cad (yellow passivate) plating looks nice but doesn't last very long on anything but a show car.
Next time when you fly an airplane and use the stick I am sure you'll be happy to know that the fasteners that hold the rudder are cadmium plated. :) ;D
There is a reason why the aerospace industry still requires cadmium plating. Zinc is not a good substitute for cadmium in many cases because among other things it is incompatible with aluminum, is less corrosion resistant, less heat resistant and has surface sticking problems.
The yellow color, whether zinc or cadmium plating was used, always comes from a second treatment with dichromate. Here are a few good pictures of the various surfaces: http://429mustangcougarinfo.50megs.com/new_page_26.htm
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Well, I have claimed to be several things in my life, but an expert on the chemical plating process is not one of them!
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FWIW in a Ferrari forum some are stating that zinc was/is the factory finish on ATE calipers.
Note that both zinc and cad, with are sacrificial coating designed to "wear away" so to speak. So if there is nothing left of the zinc or cad on your old calipers after a few decades, the plating did its job. :)
Zinc and cad are relatively easy processes to find.
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Here is a picture from a 1967 Mercedes 250SL sales brochure of the brake caliper. As I recall, my 280 SL's caliper's were black as well. nothing fancy.
John
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Zinc and cad are relatively easy processes to find.
Hello Michael,
Please, is it really that easy to get parts cad plated in the US - given its toxicity? :o
It's impossible in Deutschland - sadly. :'(
Achim
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Yes, Achim, it is easy. This has been discussed in previous posts. I've had it done as well.
Some years ago, when I began a search (after a judge told me my plating was zinc, not cad, thus incorrect...) I was told by a bunch of "experts" that you can't get cadmium plating done anymore in the USA, blah blah blah. (note: blah blah blah is American vernacular for useless talk)
Some went even as far as saying that because of EPA rules, etc. you can't get it done in California. Well, as they say, seek and ye shall find. I found two platers:
http://www.burbankplating.com/ and http://www.prime-plating.com/ In an ironic kick to the "experts" you will notice that BOTH of these folks are IN California.
Prime did some Cadmium plating for me, for Tom Rose, and I believe for Bob Possel. As I recall Bob was not 100% satisfied because of the color; remember, the gold coloring is a phosphate wash done after the plating and many factors affect the resulting color. It is hard to maintain a consistent color from batch to batch. Most people are doing this for protection not color and thus the platers are not always in tune to your needs. I was quite happy with both the gold and silver cad done for me.
If you poke around other restoration sites for other cars, you will find other platers.
Impossible in Germany? A 2-minute google search for "Cadmium plating in Germany" came up with these guys: http://www.franzplating.de/Produkte/Cadmieren.html I don't speak German but it looks they they are metal finishing in Germany, and looks to me like "Cadmieren" is cadmium plating, and that's what the photo shows on that page...just because they do it in production does not mean that they'll do restoration parts. But, they probably know their competitors and can probably discuss your needs. They can't be the only ones, can they?
I'm sure if you make some calls you can find what you need closer than California. If that Franz plating is for real, sounds like experts told you the same stuff they told me... ;)
I should add that all plating processes include nasty toxic chemicals and "heavy metals". Cadmium plating simply adds the toxicity of the plating material as well. There are a lot of tin zinc, zinc, and other kinds of "home plating" processes available for you to do this at home. I would not do it; and hope none of my neighbors are either. I would not want to live next door to a meth lab and don't want to live next door to someone doing home plating either. An industrial facility has the ability to comply with national and local rules about the handling of toxic chemicals, materials and the waste. Home users faced with disposal issues simply throw the waste down the drain, in the woods, on the street...back in the days when I was in the printing business, I paid significantly as a "hazardous waste generator" (the waste was de-silvered photographic fixer) as a tax to the state, and also paid a firm to haul it all away. Ditto in the car wash business for sludge. There are proper ways to deal with toxic waste, and they just cost money.
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Eastwood company has a paint system that duplicates yellow cad. I'm not sure if it would be compatible with calipers due to the heat that may be generated by braking systems. My guess is that if properly applied, you could get a coating that would last longer than the real deal. It looks pretty good too. I painted my warm running device housing with the stuff and it is hard to differentiate from the real plating unless you stick your face close to the part and scrutinize.
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I would NOT do regular paint on calipers to the heat as you correctly pointed out. It is not expensive to do the yellow zinc which will look better than doing nothing, or plain paint for that matter. Clear coat powder coating over the zinc will make it durable but will affect the iridescent sheen of yellow/chromated zinc.
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Do a search (outside of this forum) on rebuilding/repairing and or refinishing brake calipers and you will find a wealth of information--and opinions.
As far as paint goes, heat is one issue. Brake cleaner is another. Will take most canned, spray-on paint off quite quickly...unless you maintain your own brakes most professional shops use a lot of brake cleaner in and around the brakes when changing pads, replacing lines, repairs, bleeding, etc. Gets pretty dirty down there with that nefarious brake dust.