I do wish offset was mentioned more. I remember seeing every forum growing up say that back spacing only matters and 3.75in was the way to go and that’s all I needed to know. Well I got 10in wide wheels with 3.625in back spacing thinking that was close to the perfect 3.75in.
Now I just moved to New Hampshire with annual inspections with fender laws and I need to get the tire as close to the body as I can with minimal rubbing as possible to run a genright 4in flare and be close enough to have someone pass it since I don’t believe they’re super strict and need sidewall covered as well. I’ve had to go down this path of knowing offset and backspacing to get the idea that a jk “Moab” wheel with a 7.5in width and 2in adapter will put it at 4.25in backspacing but because of the width of the wheel my tires will be almost 3inches closer in than my current 3.6in back spacing wheels.
My old set up with the 10in wide rims vs jk wheels with spacers are less than an inch difference of backspacing but where the tire actually sits is very different.
Now my question is why is backspacing the only thing talked about when it’s the tire that rubs on things, and placement of the tire is affected by wheel width and offset too? How far the tire sits in or out is affected by all of these measurements yet we only focus on one. Because of the focus on one we fail to actually achieve the closest tire to the tub without rubbing which I assume is the intended goal and some things can change that such as outboards or swayloc making it harder without rubbing.
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I think what ends up happening is that most people don’t care about keeping the wheel/tire under the fenders/flares. They are primarily focused on making sure they don’t rub control arms/leaf springs/shock towers etc, all the stuff that is behind the tire on the inside.
I personally hate tire stick out, and so I find offset useful for comparing different wheels that are the same width to evaluate where one may land vs the other, especially with the intent of keeping them under the flares.
Jeeps are also different than say trucks, because trucks will have a more limited wheel well where if you go with too little BS or too much negative Dorsey, the tire’s scrub radius will increase too much and then just simply turning will jam the tire into the front or rear of wheel well. On a Jeep that could potentially happen, but a Jeep can be lifted above the tire and bump stops reworked to make it work. On a truck with IFS, you can’t solve it with lift unless you go with a super tall 6” or so lift that uses a drop bracket to lower all the front end components back to stock height. Lifting on the stock IFS suspension design basically just puts you towards the bottom of the suspension travel at ride height, and so you’ll still get the tire up towards the fender on bumps or offroad. So trucks are more picky and need offset to be minded to keep the tire clear on both sides.
Offset is still a relevant measurement for Jeeps though. The back of the stock wheels have the offset cast in, not BS…