i have 38 x 15.50's now. the pic with the tonneau cover up is 39.5's. i dont get a whole lot of hassle from the cops...but just some. there was a guy in va beach that had a f250 on 49" iroks and the bottom of the truck was like 6" above the tires....he told me he had no trouble with the cops but i found it hard to believe b/c he was clearly about a foot over the limit.