I have 33" tires on my 2014. The dealer can change tire size for the vehicle, but they can only select the size from a few choices. They selected the biggest tire from the list for mine. Right now at 60 MPH on the speedo I am reading 63 on GPS. At 40 MPH I am reading 41.5 on GPS.
I have not been able to come up with an aftermarket device to truly correct the speedo to date.