You'd be amazed at the crust and "ick" that grows inside calipers. Last set I did ('92 or '94 K1500) the square-cut seals had a film of rust on them that I had to peel off with my fingernail. Once that was done, and the "guts" got cleaned-up, the rubber actually seemed to be in good condition--so I put 'em right back together.
Filthy
Visible crust on rubber seal--peeled right off.
Caliper hardware cleaned up. Threads get anti-seize, sleeves get caliper grease.
Cleaned-up and going back together. Just need to slap the piston to the bottom of it's bore.
