The 275/55-20s calculate to be 31.9" tall, and I have a set of Nitto '421s that size on my '13 Limited with QL. They don't rub anywhere, any time. I drive my GC around town in Sport mode which lowers it about a half-inch.If you have a way to measure actual speed, I would be interested in what your speedo reads at 60mph.
bd