Hey guys, the tires on one of my riding mowers are a little dry rotted. They still have good tread, and they all hold air, but they are "dried" out. There is a tiny bit of cracks in them, but they are really small. The sidewalls feel kind of like sandpaper, and they are grey in color. I know getting new tires is the best option, but I can't afford that. So, what is my options to repair or "clean" them to look newer? Thanks!