Wheel Offset Explained
Offset is the distance, in millimetres, from the centerline of the wheel to the face that bolts against the hub. It decides whether the wheel sits tucked under the fender or pokes past it — and it is the number most people get backwards.
Positive, negative, zero
- Positive offset (ET35, +35): the mounting face is toward the street side of the centerline. The wheel sits further in. Almost every modern car and crossover, and most trucks as delivered, are positive.
- Zero offset (ET0): the mounting face is exactly on the centerline.
- Negative offset (−12, −24, −44): the mounting face is toward the inboard side. The wheel sits further out — the "deep dish" look on lifted trucks and Jeeps.
The number is cast or stamped on the back of the wheel, usually as ET35
(ET is German Einpresstiefe, insertion depth), +35, or just
35. It is always millimetres.
The one rule that matters: lower offset moves the wheel out, 1 mm per mm
Offset shifts the entire wheel sideways. Drop from +44 to +18 and the whole wheel — outer lip and inner lip together — moves 26 mm toward the fender. That is 26 mm more poke on the outside and 26 mm more clearance from the strut, control arm and frame on the inside. Raise the offset and it is the reverse: more tuck, less inner clearance.
In formulas, with positions measured from the hub face and W the wheel width in mm:
- outer lip sits at ET − W ÷ 2
- inner lip sits at ET + W ÷ 2
Width changes both sides at once
A wider wheel at the same offset grows equally in both directions: half the extra width goes outboard, half inboard. Going from 7.5" to 9" wide adds 1.5" = 38.1 mm, so each lip moves 19.05 mm further from center. This is why "will it poke?" needs both numbers, not just the offset.
Worked example: 17x7.5 ET44 → 17x9 ET18
A common truck upgrade — stock 7.5" wheel at +44, aftermarket 9" wheel at +18.
| Change | Effect |
|---|---|
| Offset 44 → 18 | Whole wheel moves out 26 mm |
| Width 7.5" → 9" | Each lip moves 19.05 mm further from center |
| Outer lip (poke) | +45.05 mm further toward the fender (26 + 19.05) |
| Inner lip | 6.95 mm more inner clearance (19.05 in, 26 out — net out) |
| Backspacing | 5.98" → 5.71" |
Notice the inner lip: the wider wheel wanted to come 19 mm closer to the suspension, but the lower offset pushed it 26 mm the other way, so inner clearance actually improved by about 7 mm. Whether 45 mm of extra poke clears the fender lip is a question only your measured clearance can answer — that is what the will-these-wheels-fit tool takes as input.
Poke rubs the fender; tuck rubs the suspension
- Too much poke (offset too low): the tire hits the fender lip or liner at full lock and over bumps, throws stones and spray past the body, and on some vehicles is illegal without flares.
- Too much tuck (offset too high): the inner lip or tire sidewall hits the strut, upper control arm, brake caliper or frame rail.
Staying within about 10 mm of the factory offset is a widely used rule of thumb for unmodified suspensions. It is only a rule of thumb: the authority is a measured clearance on your vehicle, and lifted or lowered trucks routinely run far outside it. Factory offsets for the vehicles we cover are on each vehicle page.
Spacers: offset you bolt on afterwards
A wheel spacer of t millimetres lowers the effective offset by exactly t. A +44 wheel on a 25 mm spacer behaves like a +19 wheel. What the spacer cannot change is stud engagement — a slip-on spacer eats thread — so the spacer calculator checks that too.
The tire can stick out further than the wheel
Everything above is the wheel. A tire wider than the rim bulges past the lip, and then the tire, not the wheel, is what rubs. The fitment tools compare whichever sticks out further on each side.
Tools that use this
Wheel offset calculator (old vs new) →
Offset comparison — three wheels side by side →
Will these wheels fit? →
Backspacing vs offset (the inch convention) →
Frequently asked
What does +40 offset mean?
The wheel's mounting face sits 40 mm toward the street side of its centerline, so the wheel tucks 40 mm further in than a zero-offset wheel of the same width. +40 to +45 is typical of factory car and crossover wheels.
What does 35 offset mean on rims?
A bare "35" means +35 mm (ET35): the mounting face is 35 mm outboard of the centerline. Compared with a +45 wheel of the same width it sits 10 mm further out — 10 mm more poke, 10 mm more inner clearance.
What does +20 offset mean?
Mounting face 20 mm outboard of center — a low positive offset. On a truck that came with +44, a +20 wheel of the same width moves out 24 mm; combined with a wider rim it is what produces the "poke" look, and whether it clears the fender is a measured-clearance question, not an offset question.
Do I want a positive or negative offset?
Match the factory offset unless you have measured room to move. Lower (or negative) offset pushes the wheel out toward the fender and adds inner clearance; higher offset tucks it in and brings the inner lip toward the strut and control arm. Within about 10 mm of stock is a common rule of thumb for unmodified suspension; lifted trucks routinely run negative offsets, but they check fender and steering-lock clearance to do it.