If you want to use a 8” wheel up front you need more than 4.5” of backspace if you want to actually use the rim width to run more tire. Realistically you need at least 5” of backspace on an 8” rim in the front to make running the 8” worthwhile vs a 7” wide rim. That Demon is only running a 225/45/17 front, so that’s only a 25” tall wheel and the specs are taken from a 7.5” wide measuring rim, so on a 7” rim the section will be a bit narrower than the spec.
In the back with stock spring locations the 5.25” backspace is a good set up for an 18x9.5”. You can’t run much more backspace than that without a spring offset of some kind.
I went back and looked at that summit wheel selection again, I’m not sure why the Summit page shows the 18x9.5” wheel with a backspace of 5.54” as an offset of +20mm. That backspace on a 9.5” wide wheel is a +7mm offset.
