ive been told you cant put different tire sizes on 4x4s because it will ruin your differentials. i currently have 285/75R16's which are 32.83 overal diameter and i want to go to 305/70R16 which are 32.81 overal diameter, just a little wider, but i cant afford 4 at a time i was wondering if that would be okay because they are almost identical in diameter, or if the width would still mess up the diffs, hell of if that piece of advice was even true. thanks.

 

diameter is important. width is not.
check the diameter/circumference of the actual tires you plan to buy. i think there is some variation in different manufactures.

edit - ^ those sizes are close enough.
if you don't use 4wd on hard or dry surfaces, then it doesn't matter - you could use any sizes.

the reason they need to be the same diameter, is because there is no center differential. its just a straight t-case. if the diameters are different, then the larger set has to slip to keep up with the smaller set. no big deal in the mud and dirt, but very stressful on dry dirt or pavement.

 

You are better off staying at 285/75 and if you want go bigger than you need to regear.

 

regear for 305s? the guy at the tire shop said theyd i wouldnt notice much more than the 285s. but i was going to regear eventually anyway. i just need 2 new tires they have about 10k left on them, and i dont want to waste money on 285's if im going to go bigger anyway

 

i got 33's and about to put 35's on it and so far nothing bad has happened

 

no need to regear, basically the same height as the others

 

you dont need to regear...its preference....im lifted and i started with 265's then went to 285's and then i jumped to 315's....which is a 35 pretty much.....and i havent regeared...

 

i wouldnt go putting 2 different size tires on yout truck though....possibly you could get away with it if they are on the same axle....but i still wouldnt do it

 

why do people just shout out widths like its the height?

 

On paper, the diameter difference between a 285/75 and a 305/70 seems miniscule. But, consider that your 285's are probably pretty warn down, and the 305's are brand new. Plus they could actually be larger then what the average 305/70 is. I would recommend you take an accurate measurement of your current tire diameter on your 285's, and then do the same with one of the 305's. Make sure it is mounted on a rim and fully inflated when you get the measurement on the 305.