Tire size conversions
 

I have a 1998 Ford Ranger 3"lift 32x11.5x15 mud tires. I bought this truck about a month ago but the tires are too noisy for me, although they are brand new from the previous owner. What kind of calculator/conversions can I use to get standard tire size (285/75/15) for example to get a radial or less rough riding tire? Thanks