THE SPARE TIRE BROKE LOOSE FROM UNDER THE TRUCK WHILE TRAVELING DOWN THE HIGHWAY, BEING THAT WE WERE PULLING A 24'ENCLOSED RACE CAR TRAILER AT THE TIME THE SPARE TIRE BROKE OFF. WHEN HIT BY THE TRAILER IT THREW THE TRAILER IN THE AIR BRAKING THE AXELS ON IMPACT. LUCKILY NO ONE WAS IN THE ONCOMMING LANE AT THE TIME OR FOLLOWING TO CLOSE BEHIND. DAMAGE WAS CAUSE HEAVILY TO THE TRAILER, THE TRUCK SEEMS TO BE OK. I AM GLAD WE WEREN'T TRAVELING DOWN A MAJOR HIGHWAY AT THE TIME OF THE INCIDENT.