I second the 303 protectant recommendation, Dave. Just keep it off the brake disks. I used to run Goodyear 4-ply Flight Custom II’s on my first homebuilt. They were 5.00-5’s & on an airplane that landed at least 25 mph faster than my Kitfox, so they had a lot more average contact time with the ground at higher speeds. The Thorp also weighed a little more than the Kitfox. I would get over 600 hrs. on a set, never swapped them left for right, and never saw any cracks like you’ve described. Just FWIW.