This may seem to be a dumb question, but I have been unsuccessful with googleing. I see people spraying there street tires before they run. Is it just water or some solution? What advantages does this give you?
It is just water to cool the tires down for more optimal temp for the AX course. Those that are pretty hardcore, will check the temp after each run and compare to what the time was. Over time, one gets a good idea of tire pressure and temp that works the best under a given course condition and types of turns and such.