First off, let me start by welcoming you to the forum. I hate to say it, but if your dealer "thinks" it's your tires???? I'd be looking for a new dealer with more knowledge. OFCOURSE the tires are the issue!! Just like changing the tire size on a pickup, adding to the circumference of the tires WILL CHANGE the gearing as well as speedo/ odo.... Im not sure of the changes yet, but plan on swapping over soon. At that point i will cross referece my onboard GPS with the speedo. A couple on here have put 32's on theirs already, im sure they will chime in and let you know what they have encountered. And again, WELCOME TO THE FORUM!!