Sorry folks for another tire question but I've been reading all the post here and other sites but I'm not finding an answer. My pup spec's are UVW 1,430 lbs GVWR 2,359 lbs The tires that are on it now are 145R12C ST type radial tires. The side walls call for 65psi but every where I look I see that C rated tires are suppose to be 50psi such as shown in this link. http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=55 And if I go onto the Calisle site the only 145 tire they show is the ST145/R12 but is listed as a LRD tire ply. http://www.carlisletirestore.com/rad_trl.htm So.... I give up trying to understand what I have and just ask what would be the recommended tire for my pup. I understand the ST is a must and radials are recommended so I guess my question boils down to brand and size. I really don't want to go out and buy 3 new tires and rims right now as I "think" the tires are ok right now but when I do need to replace them should I or could I go up to 13"?