Try another brand 275 like BFG and you'll see it's a lot more than 1 or 2mm. The Nitto 555R also have more rounded shoulders so the flat contact area is less. I've had both on my car and the difference is substantial. The NT05R will be a better tire for the OP drag racing if he sticks with Nitto. Being an auto he probably won't have spinning problems like the M6s
i tell you right now, i went to a used tire shop, and a michellin 275, think it was power something, put it agianst my nitto 285 555R and it was the same width, right. the only difference was that the nitto was mounted on the rim and the michelin was not. ok so i am thinking that svede guy was right, the nitto runs smaller. anyway, i put a 285 pirelli p zero aginst my nitto 285, and what do you know, the pirelli is wider by about half an inch to a 75% of an inch. the only difference was, once again, the nitto was mounted on the rim and the pirelli was not mounted on the rim. so i think to myself, that svede guy was right, the regular 285 does run wider then nitto 285. Now get a load of this;
i mount the 285 pirelli to the rim and compare the tires now, with both being mounted to the rims, and what do you know, the size is the fricking same, no difference. due to nitto not having steel sidewall as other brands they are 1-3mm narrower, but the traction pad is the same.
so i am assuming that when you compared your BFG tires to nitto, both brands were not mounted. am i right? there is a lot of variance between brands, but it helps to norrow down as many factors as possible to get it to the same level in order to be compared.
from what i learned, it seems that the tire streches outward, being round, so it shrinks in width once mounted to the rim.