Recent 19+ 40 Inch Tires. Going over how much $$$ it takes to drive on 40's, mpgon 40's in town, on the highway, & the interstate. Find all 40 inch diameter tires for every wheel size, including the metric and inch equivalent tire sizes available for each tire. Lastly the most important question most people have. I was looking into running 40 inch tires on my jk and was wondering what i would need to do to successfully run them on my jk.