Originally Posted by shortride
I swapped my OEM 18's for OEM 20's off of an FX4. There is about .785" difference in diameter between the two tire sizes.
That's because you did not chose your tires properly!!
If you have 265 65 18 for example, a tire size of 275 55 20 will have about the same dimensions (within 2%) thus, the speedo, odometer, and overall heaight will be close to OEM. Rims are only 1 dimension.
Re: sidewalls riding harsher- I'd challenge anyone to blindfold themselves, get in to 2 identicle trucks. 1 with 55 profile, 1 with 65 profile and clearly identify the "harsher" ride. Ain't gonna happen.
Use this site to size tires: