Just a little tip. I have rebuilt hundreds of brake cyls with good results,but in working on firetrucks I had poor results in rebuilding them.My thoughts are when you over bore the cyl and it sets for long periods the pressure drops off and allows the cup to relax thus it leaks. To verify this I would go by the fire house every week or so and pump the brakes. As long as I did this they would not leak.Just more stuff based on real world expierence.
