Vehicle · Wheels
Wheel offset change calculator.
See how far a new wheel (and wider tire) moves toward the fender and toward the suspension.
Current and new wheel
What moves
Enter the details to see the result.
How do you work out how far a new wheel will stick out?
The hub mounting face does not move, so everything is measured from it. The inner lip sits at the backspacing distance inboard of the face and the outer lip sits at the frontspacing distance outboard (overall width minus backspacing). Subtract the current wheel's figures from the new wheel's to get the change at each lip. Lowering the offset by 15 mm (for example +45 to +30 mm) with the same width pushes the whole wheel 15 mm outward, which is the example given for flush fitment on the Wikipedia wheel offset page.
A wider wheel at the same offset grows by half the added width on each side: going from 8 to 9 inches at +35 mm moves each lip out by 12.7 mm. A wider tire adds roughly half its section width increase on each side as well. Track width changes by twice the offset change, because both wheels move. Too little clearance outward risks fender rubbing, and too little inward risks hitting suspension or brake parts (Wikipedia).
Frequently asked questions
How much does 10 mm of offset change the wheel position?
The whole wheel moves 10 mm. Lowering the offset by 10 mm moves the wheel and tire 10 mm outward toward the fender and 10 mm away from the suspension, and widens the track by 20 mm across the axle.
Does a wider wheel change how far it sticks out?
Yes. At the same offset an extra inch of width moves the inner lip 12.7 mm inward and the outer lip 12.7 mm outward, because the width is split about the centreline.
How do I include the tire?
Enter the current and new tire section widths in millimetres. The tool adds half of the width difference to each side. It is an estimate, because the tire profile also depends on the rim width and brand.
Is this enough to know a wheel will fit?
No. It shows the change only. Brake caliper clearance, suspension travel, steering lock and fender rolling all matter, so check with a tire shop or the wheel maker.
Sources
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Scope
This is geometry from the numbers you enter. It does not check clearance on your vehicle. Confirm fitment with the wheel maker or a qualified tire shop.