Best tire rating for the desert heat?

[the_same_mountainbike]

The key here is keeping the proper tire pressure rather than the speed rating. When tires are underinflated they flex and squirm more, and that generates heat, and combined with high heat can result in failure. Higher speed ratings can help, simply because they typically have stiffer sidewalls and produce less flexing and squirming under a given set of circumstances, but I think the real key is a good pressure gage.