My 1987 samurai hasP275/60 R15 when I first got it. The rim don't look like it came with Samurai. I dislike the size. What next smaller size that will fit on 15" rim? Most of the time I use it on the farm and few time on Farm market road within 15 miles radius from my home. Is P185/80 R15 the original manufacture tires for my samurai?