In order to keep the truck as low as possible for my 5th wheel, I want to order the LT275/65R 18E tire instead of the LT275/70R 18E tire - this is an option. This lowers the bed by about .5 to .75 inches (every little bit helps). Does anyone know if they recalibrate the speedometer or do they install diifferent gears in the speedometer when you order a tire different from the one that normally comes with the truck? Can this be done by a dealer if you change tire size later during the life of the truck?
Thanks for any info.

 

The dealer changes a setting in the PCM and the speedometer will then read correctly. I had this done when i went from the original 18's to the optional 20's.