Another slang term for the Canadian hardware store "Canadian Tire", also known by most people as "Crappy Tire". "Shitty Tire" is used as a replacement noun in cases where the term "Crappy Tire" doesn't quite cut it anymore
Steve: "Hey, man, is your car still at Shitty Tire?"
Bill: "Yeah, they ripped all four of my tires and need to wait 2 weeks for new ones to come in, so I can't drive it until then"
Steve: "I wouldn't take my wheelbarrow to Shitty Tire"