i have a 2wd 03 f150 and have 285/75/16 on 16x10 inch wheels...looks pretty sweet. i will put a leveling kit on there too in the future. but i was wondering with a V6 engine can i put a 33x12.5 or 33x13.5 tire on there without regearing and all. how bad will that hurt my gas??? thanks guys

 

Anytime you increase tire size without adjusting tire size/gear ratio, you are going to affect gas mileage. Especially with a V6

 

Your 285/75-16's are 33 inches tall. You will just be going to a wider tire. You will increase rolling resistance slightly, so milage may decrease.

 

yea i figured id lose a little bit...would it be better if i put new gears in???how much mileage would that help?? 13.5 be too much? or 12.5 would be the best probably

 

Your tires now are 32.9 tallx10.3 wide. So, as wandell said you will only be going wider.....A wider tire will weigh a little more so you will lose a little gas mileage due to increased rotating mass.

Now, if your intention is to do a leveling kit eventually, you may be better off holding off on the 33's. With a leveling kit you can go with a taller tire.

Basically this should get you pretty close as far as gearing:

present gear size / present tire height = y

y x new tire height = new gear size needed to keep same tire to gear ratio

For example:
My truck had a 29" tall tire with 3.73 gears so,
3.73 / 29= 0.1286

0.1286 x 35(my new tire size)=4.50

So, to keep the same ratio I would need something like 4.50 gears, 4.56 are the closest so a 35" tire with 4.56 gears would keep my tire to gear ratio close to the same....

 

285-75-16 are 11.3 or so not 10.3 wide!