Understanding offset and backspacing
Why ET decides whether the wheel rubs.
Offset, written ET, is the distance in millimetres between the mounting face and the centreline of the wheel. Positive offset pulls the wheel inward, negative pushes it outward.
Dropping from ET+30 to ET+0 moves the wheel 30 mm further out. That changes clearance at the strut, the fender and the control arm all at once.
Backspacing measures the same thing from the inner lip instead. Either is fine, as long as you tell us which one you are quoting.
More guides
Forged vs cast vs flow-formed
Which process actually matters, and what you are paying for.
How to measure a bolt pattern
Getting this wrong is the most common ordering mistake.
Choosing skid plates: aluminium or steel
Weight, cost and what actually protects.
Choosing a winch: capacity, rope and mounting
The 1.5x rule, and why rope choice matters more than most people think.
Roof tents: how to work out if your roof takes one
Dynamic vs static load, and why the number on the rack is not the number that matters.
Do differential covers actually do anything?
Separating the real benefits from the marketing.
Load rating: the number to actually check
The spec that decides whether a wheel is safe on your vehicle.