STINK described the proper procedure for making sure the parking brake does not engage. Caging the parking brake spring canister
(utube video) (written procedure)
is what must be done prior to towing/moving any vehicle with failed air brakes. NOTE! The very first thing to do is solidly chock the vehicle from moving!
High humidity may be causing the brake drums/rotors to rust. Rust holds the brake lining to the drum/rotor.
If that is not your situation, it can be the air brake linkage at the wheels- if that hasn't been greased on schedule, which would allow the linkage to rust in-place.
2000 Winnebago Ultimate Freedom USQ40JD
, ISC 8.3 Cummins 350, Spartan MM Chassis. USA 1SG, retired;PPA,Good Sam Life member."We the people are the rightful masters of both the Congress and the Courts - not to overthrow the Constitution but to overthrow men who pervert theConstitution. "Abraham Lincoln"