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Wheel Offset & Fitment Calculator

Visualize the difference between a current wheel setup and a new setup. Calculates exactly how much further the wheel will poke out or retract towards the suspension strut.

Math Engine Online
Wheel Specifications
Enter the width (inches) and offset / ET (mm).
Old / OEM Wheel
New Wheel Target
Fitment Results
Inner Clearance (Strut Side)
-5.7 mm

Closer to the suspension strut

Outer Poke (Fender Side)
+19.7 mm

Extends further towards the fender

Wheel Fitment Verification

Offset calculations are geometric only. Always verify:

  • Wheels clear brake calipers and suspension components
  • Fender clearance with your suspension setup
  • Tire sidewall remains clear of body/frame
  • Load rating meets vehicle weight requirements

Methodology

Backspace: Distance from wheel mounting face to outer edge

Offset: Distance from center of wheel to mounting face

Frequently Asked Questions

What happens if wheel offset is wrong?

Wrong offset = wheels too far inboard or outboard, causing rubbing on suspension/body or change in track width. Always physically verify fitment before driving; don't trust calculator alone.

Does offset affect handling or turn-in response?

Yes. More positive offset (wheels inboard) affects steering feel and bump steer. Track cars sometimes run negative offset (wheels outboard) for wider stance, but requires wider fenders.

Do I need an alignment after changing wheels?

Not always, but offset changes can shift camber/toe slightly. If you swap wheels (change offset significantly), get a 4-wheel alignment to be safe.

Disclaimer & Legal Notice

All tools and calculators provided by Lapsite are for informational and educational purposes only. While we strive for mathematical precision, these results are approximations and should not be used as the sole basis for critical engineering, financial, or safety decisions. Lapsite Ltd and its creators provide no warranty, express or implied, regarding the accuracy or fitness of these calculations for any specific use.Always double-check calculations independently, especially for safety-critical components such as brakes, suspension, or structural changes. By using these tools, you agree that Lapsite Ltd is not liable for any mechanical failure, financial loss, or injury resulting from the use of this data.

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