My 2010 GMC only has 16,000 Km (10,000 miles). The tires look really good - no cracks - I will not be changing them because they are 6 years old! The tires are General "Grabber"
I bet that if I did buy new tires, the dealer would put my old ones on someone else's truck. They sell used tires all the time.
I will keep an eye on them and if cracks appear, they will be changed.
