What kinds of vehicles are rolling on 245/40R18 tires? Think Ford Mustang Shelby GT500, Mercedes-Benz CL-Class, Maserati Quattroporte, and other vehicles that are engineered to go fast. If you’re lucky enough to drive one of these, chances are you’re looking for ultra-high-performance tires that up the performance game. Just remember that for ultra-high-performance tires, the tread compound is softer and “stickier” for enhanced grip, meaning they will stiffen in colder weather and shouldn’t be used when temps are below about 45 degrees Fahrenheit.