You stated that the 305/55r20's were wider than the 305/50r20's but by the calculater I use, that is incorrect. The only variation in dimension should come in the diamter. How did you come about those dimensions? I know that when I had the 305/50r20's on my Lightning wheels, the front tire had less than a half inch of clearance at the UCA. I don't think you can fit any wider of a tire with those wheels. Now that I think about it though, that was at 2" of drp in the front. A wider tire may fit at stock height but I think it would cause problems under compression.

Hello, Do you think 305-55-20 on Ford Racing 20x10 Lightning wheels will not rub on an unlifted 2005 f150 4x4. 305-50-20 are 31.9 OD and 11.9 wide. 305-55-20 is 33.2 OD and 13.2 wide. I think the wide measurement is at the bulge of the tire. I want to leave stock front height and lower the rear 2 inches. Thanks, I like your truck at any evolution it is in