Tires: tire upgrade on stock rim, stock wheels, exact sizing

Question
I have a 1991 Ford F150 4WD with stock wheels and tires(LT 235 75 15) I would like to put 285's on the stock 15" rim somehow. What is the exact sizing I need? If I cant go as big as 285's what is the absolute biggest size I can get without getting new rims?

Answer
Cameron,

 You are experiencing a dilemma that many of my customers and me faced.   There are few choices for the 15" x 8" or 8.5" rim.  If your truck has the clearances a 31x10.50x15 is going to be the largest tire you can safely mount on the stock rim.


Hope this helps,

Brett