Offset and new wheels

[Drewmcg]

I'm purchasing new wheels for my 2010 Explorer XLT--nice looking, darker grey ones to go with my dark grey late-build model.

I have P235/70R16 tires, and plan to stick with them. New winter tires are going on the old rims (actually, old rims from a 2002 explorer, which raises a separate TPMS issue...). The seller offers 5-bolt, 114.3 mm (4.5") bolt diameter 16" rims in two offsets: 48mm and 38 mm.

The original Ford aluminum rims are 44mm offset. So I have to err on one side or the other.

Question: I'm not worried about the tires extending out a couple of millimeters (no way I can see that they will touch the fenders); but I most definitely do NOT want to experience rub between the brake calipers, on the inside of the rims, and the new rims.

My understanding is that the 38mm positive offset will be the better choice to address this concern. In other words, the larger the (positive) offset, the closer the rim rides to truck (effectively, a narrower track). That might eliminate the required spacing between the inside of the rim and outer surface of the caliper.offset.

Is this correct? TIA.

 

[dacaur2]

Yes and no. Yes the 38mm offset will be less likely to cause problems, but not because of the brake caliper. Offset will not in any way affect caliper spacing. The inside of the wheel is a flat surface, and no matter where that surface is in relation to the center of the wheel (which is what offset is, the distance of the mounting surface to the center of the wheel), the calipers have the same amount of room.
What it will affect is where the inside surface of the rim, and therefore, the inside of the tire, sits in relation to your suspension and inner fenders. Move that too far in and you will rub the tires on suspension components or your inner fenders when you turn.

A more important number in this case is wheel width. If your new wheels are the same width as your old wheels, then the 4mm or 6mm difference in offset (just over 1/8" or just under 1/4") wont make much difference and probably wont cause any rubbing no matter which one you choose.

(If your new wheels are the same width, you can skip this next part, as it can be confusing)
But if your new wheels are wider, it can make a HUGE difference, because then you have to take that 4/6mm and add half the difference in wheel width. So for example if your stock wheels are 7" wide with a 44mm offset, and the new ones are 8" wide with a 48mm offset, thats a 1" difference in width and a bit over 1/8" difference in offset, so you take half of that extra inch, and add the extra 1/8" offset, and that gives you a bit over 5/8" farther in that the inside of the wheel (and therefore the tire) will sit toward your vehicle, which will very likely cause rubbing when you turn. (on suspension components and inner fenders, not brake calipers)
Go with the 38mm offset,and that 5/8" turns into only about 1/4" farther in, which will almost certainly be just fine and not cause rubbing. (the difference moves to the outside, allowing the tire to stick out further, which if you go to far can also cause rubbing, but it shouldn't be an issue since you are not going up in tire size.

Confusing I know. Thats why most aftermarket tires make backspacing the most prominent measurement, because wheel width doesn't affect backspacing like it does offset..... if a 16x7 with 4.5" backspacing wheel clears all your suspension components, a 16x8 with the same backspacing will as well..... But.... offset is still important, because large changes in offset can seriously affect handling....

TL : DR, get the 38mm offset.....

 

[Drewmcg]

Very helpful. Thanks a ton.