Hi everyone, I am new to this forum. I have an 86 F250 4WD Diesel with horrible worn out tires. I like to off road (slowly). What is the biggest tire I can go without lifting or changing rims? Any advice on size or even tire recommendations are appreciated. I am running Nitto Ridge Grapplers on my Ram and really like them.

 

stock for that truck is a 235/85R 16 = 32 X 9.50 X 16 on a 6 inch wide rim.
this is about as wide a tire you can go on the stock rims.
285/75R 16 = 33 X 11.50 X 16 is about the biggest you can go without rubbing
you can go up to a 315/75R 16 = 35 X 12.50 X 16 with minor trimming of the front bumper,
and minor rubbing on the springs on full lock turn.

for either of these tires, i would recommend increasing rim diameter from the stock 16X6 to a 16X10 rim.