I'm busy ordering black xd monsters(wish i could get it in bronze). What is the correct offset the 18mm with 5.71 backspacing or 35mm with 6.38 backspacing? Its on 18 x 9.
I'm putting 33 toyo mt's on it. Allready installed a 3" OME levelling.
You could get away with either since youre only putting 33's on them. However if you ever get the notion to go 35s youll want the +35.
Well, put it this way, the higher the + number the more the wheel is tucked in under the fender, so a +35 will be tucked in more than the +18. However there are a couple areas of "rubbing". The first has to do with the UCA (Upper Control Arm). That has to do with both the width of tire and how close the wheel is to the interior of the truck. You can measure how close it is to your current tire and use that space to calculate how wide a tire you can take and how much offset you'll need to accommodate it. For example, if you have a 275 tire on the stock +60 rims and you find that you have a 1" space between the side of your tire and the UCA, you can add up to almost two inches of tire before rubbing on the UCA (since they would be evenly split with 1" on both sides) with a rim that has the same +60 offset. So, for example, a 325 tire is 50mm more than the 275. Technically two inches = 50.8mm so you would barely have any space between the UCA and the tire all things being equal. But, you should also know that a tire is based on a standard rim width. Every .5" of extra or less rim width = approx. .2" extra/less of tire width (tire meaning the bulge of the sidewall obviously and not the tread as that doesn't change). Now say you put this 325 tire on a rim that has a +35 offset. you will now have moved that tire the equivalent of an extra +25mm outward. If your rim is an extra .5" wider than the tested width for this tire, than you're only looking at around 20.4mm space between the tire and the UCA because the extra .4mm from the original space plus the extra 25mm from the offset would be partially negated by the extra .2" (= ~5mm).
The second area of rubbing is in the fender well. The greatest areas for this is where the outside edge of the front of your tire reaches the mid-point of the turn and where the inside edge of the rear of your tire reaches the mid point of the turn. These equate to the area that needs the most length in the fender-well. The wider the tire tread (and the larger the diameter of the tire), the greater the protrusion or total length of the turned tire. If the max area of this midpoint turn falls too close to the outside of the fender where the curve of the fender dissipates, you'll have rubbing in the fender-well. This can be exasperated by having an offset that pushes the wheel outwards.
Another potential area of rubbing that is much more common, but also much easier to deal with is the rubbing that comes from the turned tire hitting the corner of the skid plate. That can be resolved simply by bending part of the skid plate away from the tire... about 1/2" is all that is needed for that and it is quick and easy to do.
Anyhow, this isn't an exact science, but you can see that there are a lot of things to take into consideration. I just mentioned a few of the more expected issues to look for and the more common calculations you can make to get a good idea or make a decent determination of the possible outcome with your desired wheel/tire combination. Good luck and feel free to ask questions!