3.75" backspacing on 15x8 or 16x8 wheels is the XJ baseline — it keeps tires out of the fender and gives proper track width.
Backspacing measures from the wheel's mounting flange to the rear lip. Less backspacing pushes the tire outward, increasing track width and clearing the fender wells at full stuff, but adds bearing/ball-joint stress. The XJ standard is 3.75" on a 15x8 or 16x8 wheel — this provides enough fender clearance for 31–33" tires without overhanging like a poke build.
4.5" backspacing is too much for anything bigger than 30s — the tire hits the inner control arm and fender liner.
3.5" backspacing is fine for 33s+ but starts to require steel flares for legality (poke laws vary).
Most aftermarket steel and alloy XJ wheels (Cragar Soft 8, Pro Comp 69, Method 105 Beadlock, etc.) ship in this 3.75" range. When in doubt, measure your current wheel and order matched.
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.