I’ve been working on Mike’s Ferrari 365GTC/4, and on the first drive the front brakes started to seize up. From what I can see, Mike didn’t get a chance to drive this car a lot the last year or two, so I wasn’t surprised they were having problems.

I ordered a front brakes seal kit, pulled the front calipers off, and blew out the pistons to take a closer look.

The original pistons were chromed steel, but upgraded replacements were made from stainless steel. Luckily, these pistons were the stainless replacements, so I simply had to polish them up and they would be good to go. They siezed because of the small ridge of rust that formed on the cast iron caliper body and the piston past the seal behind the dust boot. (You can see the rust ring that stained the stainless steel piston before I cleaned it up with some fine sand paper.) I think disuse, and damp storage formed this ridge, and built up enough to jam the pistons so they wouldn’t retract. I put a new seal kit on the front calipers, and disassembled the rear calipers to clean up the rust ridge that was forming and about the seize the rears as well!