Wheels for a duster offset and backspace

QMopar said
When I bought my Dart Sport, it already had 18s: 225/40-18 in the front and 245/35-18 out back. I have no idea what backspacing is on these wheels (is there an easy way to tell?). I'm thinking I'd like to run all four of the same size wheels/tires so I can rotate tires and only carry 1 size spare. Ideally I'd probably like 17's but I read that 18's give you more clearance for front suspension items. Could anyone share their experience with one size for all 4 wheels/tires? ThanksView attachment 1715288300

I still don't understand why a person would worry about offset, the back space is what really matters for wheel fitment ,if the back space aint right , it wont work if ur pushing the limit on wheel/tire size.
I have to have a 3 1/2" back space with my rear end length, and tire / wheel combination, I could care less about the offset in mm measurements.???????