they fail OPEN. Correct me if im wrong guys but I believe you still have SOME braking power even if you lose air pressure? but if the hydraulic system has a leak you have no braking power.Another question I forgot to ask. When the brakes do fail on a M35 do they fail open or closed (locked)? I know on a lot of military trailers with airbrakes the air supplied keeps the brakes open so you can tow it and they fail in the closed (brakes on) position, so no air and you're just dragging the trailer and smoking the wheels.