Cooper Discoverer A/T3 & S/T Maxx Tire Review. Posted in How To: Wheels Tires on July 1, 2011. Share this. Ken Brubaker Editor, Four Wheeler. Recently, we were invited to the Cooper Tire & Vehicle Test Center (CTVTC) in Pearsall, Texas, to see the all-new Discoverer A/T3 and S/T MAXX tires.