Restoring a set of Turbo Calipers

I was given a set to restore a few months ago but they were in such bad shape, we ended up Cerakoting them vs restoring to original anodized condition. Those turned out beautifully but when I received another inquiry on restoring a set, I was eager to see how they would turn out.

Calipers as received. Notice how the piston housings are darker than the bridges. Turns out they are different aluminum alloys so they anodize differently and take up color differently. Did a fair amount of testing with various processes to even out the color but they will never match 100%. My anodizer does a lot of military work and we ended up using some special chemistry for a certain black helicopter. I, and more importantly the customer, are happy with the results.

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After disassembling, the seals and scraper rings had to be removed before stripping the old anodizing off. Seals pull out easily. Factory technique for removing the rings is to dent them with a small chisel or punch. I made one and it worked ok. Better process was to grab the lip of the ring with a small pair of wire cutters and twist. Doing that a few times shrinks the ring and they pop right out.

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Caliper pieces stripped of anodizing. As with window frames you want to be as gentle as possible with the stripping solution as it will start to attack the bare aluminum while other areas still have anodizing. Better to chemically strip as best as possible with minimum attack and then physically remove any remaining anodizing. The goal for these was when the piston bores were clean, they came out of the stripper.

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Remaining anodizing was removed in the media cabinet and then the whole top side of each piston housing was evened out. From there they went into the tumbler for a while to create a good clean surface for anodizing.

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Even though there is practically no chance any media could be left in the passages after being tumbled, I spent a good 10 minutes on each caliper making sure they were perfectly clean.

First use Cerakote hanging wire and then with welding wire and then water pressure and a final check with light in both light and dark room settings. There is a greater chance of debris being in the calipers passageways when they were made than now.

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I thought I had taken pics right after anodizing but apparently not. Next step is to remove the anodizing over the PORSCHE lettering. These are sand cast and machined so even though this was done at the factory when first made, this proved more challenging than I anticipated.

Tools used. The pneumatic pen spins at 56,000 RPM. An amazing little tool.

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Taped up and started filing away. Very uneven surface on this particular half.

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After a little work and then cleaned up with the wire brush on the pen.

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Finally time to get the seals and scraper rings in. Tumbled/polished the pistons and then lubricated the seals with Sil-Glyde, worked perfectly, I used a bearing press disc with some duct tape to press them in place. The pistons are stepped to reduce contact with the pads which reduces temperature transfer from the pads to the fluid. Front calipers, the step is on the lower side, rear calipers the step is on the top side.

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All done.

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All hardware was stripped of plating, tumbled and then replated in yellow zinc. Got the pistons in and the pad plates with retaining springs. Sil-Glyde worked nicely on getting the springs in. New screws for the plates.

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Hardware ready to go. The brass banjo fittings polished up nicely.

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Built back up and ready to go.

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Thanks for the kind words. These are $900 per pair. A little more than PMB but I think worth it.