Nankang makes a tire 21X12-8 NK N800 SLICK TREAD 2 PLY. No trimming required. I personally have no experience with them but other kitfoxers have good reviews I'm still running the original 21" kitfox baldies. Here's a link to some I found online. http://www.atvtires.net/productdetail.asp?gn=N800
Nick