The phrase "tire sidewall" refers to the side part of a tire. It is the area between the tire tread (the part that touches the road) and the bead (the inner edge of the tire that attaches to the wheel). Full definition
The taller tire sidewalls of the LT ate up more undulations than the thinner rubber on the Premier, but all that tire led to plenty of road noise making its way into the cabin below highway speeds. (cnet.com)
The result is a dynamic driving experience on - road that can take you anywhere within the limits of tire sidewall and body damage off - road. (fourwheeler.com)