the OEM tires where 17, the original selling dealer put on these 20's, so they are about 2 inches taller, plus this has the 2 inch lift kit,
as for the calibration, it will depends on the trucks computer. Odd part with mine being a 2500 the only pinion setting we can see and adjust are for the 17 wheel NO 20 inch setting like the 1500's have. So this may be predetermined by the factory.
added some factory decals and non factory stripes.