This is true. The Nitto 555R is 1/10th of an inch narrower overall than the 555 (10.9" vs. 11") but it is the same width (overall) as a Goodyear F1 GS-C or a BFG G-Force KD. Nitto does not provide tread width information but the tread does wrap around the shoulder of the tire quite a bit.
468LC - You make a very good point and maybe I shouldn't generalize based on my own experience. I was able to feel a noticeable difference when I put 245's on my 7" rims. After doing my homework, I have realized that all the well handling cars in the world have conservative rim/tire combos. A 275/8" combo is more aggressive than a 245/7" combo. With all due respect, I know that rim/tire combo is used all the time but some people can feel the difference. I guess if 245's on 7" rims feels good, then you shouldn't have a problem with 275's on an 8" rim.