WAS PULLING A TRAILOR WITH TRACTOR AND BUSHHOG ON IT. 3 CARS WERE STOPPED IN FRONT OF ME. THE FIRST ONE TURNING LEFT. I WENT TO STOP. BRAKE PEDAL WENT TO FLOOR. HITTING THE VEHICLE IN FRONT ME, PUSHING THAT ONE INTO THE ONE IN FRONT OF THAT ONE. UPON INSPECTION BRAKE LINE UNDER DRIVERS FLOOR HAD BURST OPEN DUE TO RUST. TRACTOR ALSO CAME FORWARD EVEN BEING STRAPPED DOWN BREAKING THE HEAD GATE ON TRAILOR. GM NEEDS TO STEP UP TO THE PLATE AND FIX THIS ISSUE WITH THESE TRUCKS. VERY LUCKY NO ONE WAS KILLED OR INJURED. *TR