The rear calipers on this 246GTS I have at the shop had a set of seized calipers. Instead of simply replacing the seals, I decided to replace the pistons with new stainless steel pistons readily available from the Dino aftermarket. The replacements looked great and identical to the original pistons except for one crucial measurement, the outer diameter!! I took my micrometer out and found the stainless steel pistons were just about 1000th to a half a thousandths too thick so when inserted into the stock bore of the caliper, they didn’t slide as nicely as the original ones.

Taking such a little bit of material is not so easy as it’s not enough for a tool on a lathe to cut, so polishing if off with some Emory Cloth was the solution. The stainless steel didn’t turn down very fast, but with patience, I got it to fit and slide easily. As I was working on these pistons, I wondered what every other shop working on Dinos were doing? Were they checking the fit of these pistons or were they just jamming them into the bores?

After I got the piston diameters sorted, I pressed in the parking brake self adjusters into place. The rest of the rear calipers when back together without issues, but I had my fair share of challenges with these Dino rear calipers!