Familiar look, unique build. The Tire Rider Tuff tire cart is equipped with a clamp closing mechanism; a strong and solid steel spring with a lifetime warranty. No more gas shock. The Tire Rider Tuff tire cart has been thoroughly tested; its strong structure and mechanisms have been pushed to the limit to make it your go-to cart in the shop.Testing of the mechanisms (breaking points):756 000 opening cycles on clamps, representing 31½ years of use (100 strokes/day X 240 business days)432 000 activating cycles for the spring, representing 18 years of use (100 strokes/day X 240 business days)Weight testing:201 600 back & forth cycles with a load of 550 lb/250 kg