I changed front and rear tires on my 400 Wednesday night before riding Thursday. Everything was difficult. Actually, I let my son do the front tire, for some experience. Took about an hour. Then I did the rear, pinched the tube, and had to re-do it. Took about an hour, too. It was a real stiff Dunlop 739 AT, the 7-ply desert tire that weighs twice as much as most rear tires, and it was a bugger. It was all worth it, though, because my new D773 up front and Pirelli MT32 in back worked fantastic in the mud, and contined to stick like glue through out the day as it dried up.