got a flat on sunday,spun the tire on the rim and tore the stem off the tube to boot.when i took it apart the steel cable in the tire bead was broken in one spot, stickin out like a piece of barbed wire,anyone ever had this happen? the tire has only 40 miles of trails(new this season),its a dunlop 756 .i'm not sure why the rim lock didn't hold the tire,any tips on how to ensure a good bite on the bead with it? thanks for any info!