[mkiv808]

What's going to give you more tread contact, 275's on 9" wide wheels or 255's on 9.5" wheels?

 

[Mark Conte]

find the rim width that specific tire is meant for (depends on the aspect ratio) then if you are going bigger (like its meant for a 9 inch but you put on a 9.5) instead of X contact patch, it will have approximately X + .2 inch contact patch, same way if you go down a half inch, it should lose about .2 of contact patch