I am running 20" Nitto NT05R Rears and NT555R Fronts, the diameter of the fronts are 91" and on the rears 91 5/8" on OEM rims. Is the 5/8" variation acceptable? How picky should I get? This is the closest match I can get on 20"s for the Nittos. Is it acceptable to play with lower tire pressure in the rear vs front to get the diameters in line? Sorry for the newbie question!