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in the everlasting "re-production" of my 2.4S, it's now time to see what can be done about the brake calipers. The use of hard-chromed or stainless steel pistons is a discussion in itself, but my question is regarding the caliper; Does anybody have experience with "gold-zinc"-ing the M-calipers? (the front S-calipers are o.k.). Should the calipers be split to do this? (so changing the O-rings)?
thanks
Tom
Hello
Yes they need to get splitet but I know people who diped them complete and they look nice and it is much cheaper. Only problem is that they corrode fast after several months and i would never trust them.
Front calipers rebuild is very simple as there is only one company able to do it and meet ATE/Porsche standards.
Also Manfred Rugen was developing a titanium piston to replace the aluminium unit but I don´t know how this project worked out and the price will be to high for street use.
Grüsse
Hi Roland,
what do you mean with "I would never trust them"..; You mean the zinc coat lets loose? Or do you mean the replacement of the O-rings which make the calipers less "trustworthy"?
Hi Tom,
Sounds like the restoration is continuing. White Post Restoration claims to rebuild calipers by resleeving. They have ads in Autoweek and some Vintage Racing mags.
To properly yellow-zinc plate the M calipers, you may need to split the calipers. Another alternative is using a paint that looks like yellow-zinc plating. It's sold by Eastwood Products.
Sherwood
Hello
The prozess needs to bath the parts into different solvents who are not to friendly to rubber.
Yet the capilar effect sucks in those solvents and they can´t be washed out full. They wil start corrosion on the surfaces and also the seals beteen the parts will get eaten up.
The best way is you put a rubber part into battery acid and have a rapid look on the process.
Yet at galvanizing it is a 5% solvent.
A other problem is that it will only coat the outside from the caliper and only if the operator knows his stuff he will place it correct to the electrodes.
Mostly you can see they didn´t cared about it and just diped it in and let the processtime go to the max to have some galvinization into the bad corners too.
This is also starting a to weaking the part and "burn" the surface by hydrogenisation.
A good working company will try to work as fast as possible and use to bath the parts in hot oil to have the good looks in the corners and on the surface as weel ( depending on the condition and the craftsman it can look like polished )
The best is always to ask your local galvanizer.
Maybe he has a other view and I got always riped off from my local galvanizer but I had seen enough fast jobs and the caused problems to avoid that.
Grüsse
Were they originally Zinc and Gold pass or were they blue Zinc
prior to years of grime accumulation. Can anyone tell me as I wish to do the same but to original specs whatever that was.
Clyde Boyer
Hi Tom. I restored 2 sets of M calipers without splitting them (yellow zinc) and never had any problems. What I did was remove the pistons and seals and closed the holes with press fit rubber plugs and plugged the fluid line hole with a steel plug. Then I silica blasted the outside surface and finally completed the outside finish using a vibratory finishing machine with carbide media.
The end result after plating was excellent concours quality. Then I removed all plugs, cleaned all passages and reinstalled new seals and pistons.. Complete.. Never had a problem since. Maybe I'm just lucky, but like Roland say's, you have to be carefull with the acids and solvents in unwanted areas.
Goodluck, Robert.
P.S. Hey Tom. If your planning that early S meet in Europe next year, my place is open. Theres lots of space for parking, the view is beautiful overlooking the Main River and the Spessart forest, it's in central Germany and we could have one hell of a BBQ. (not to mention the twisty little Bavarian roads for a little tour around the country side) Sure would like to see this turn into a Eropean Cambria.
Just food for thought.
Robert
Hey Robert e.a.,
thanks for the info.
Well, the remark of the "European Chapter" was more like a joke... But, since more and more people are taking this serious, let me think about it. I had a discussion the other day with the (co)founder of the Dutch Classic 911/912 club, on a parts market (we went to Veterama, Europe's largest classic bike and car parts market, with no/hardly any Porsche parts)... Maybe it's better to post a separate topic in the general forum on a European event. Please add your comments there.
Thanks again
Tom