I have no idea why, but maybe this guy thought it would be bad for his power to weight ratio to bring along spare rims with tires on a drift session. So he only brings along a spare tire and some tire changing tools!
First he starts to separate the tire from the bead on both sides which takes him roughly six minutes to finish. Unfortunately the video stops after they guy explaining the next steps. But I can imagine he would be sitting there changing his tires the rest of the day! :D