I have a MAX IV that I need to replace 2 tires on. They are Goodyear Rawhide 22 x 11 x 8..Does anyone know of a source in SE Michigan or a store that sells them on-line ? I keep losing air pressure and can't find any leaks in them even using soapy water. Also, where are the drain plugs located in the tub ? Thanks for any help from another old new guy