Wheel offset & tire size comparison — visual geometry report
Compare two wheel and metric radial tire specifications with shared-scale cross-section and diameter views. Keep wheel bead-seat geometry separate from nominal tire width, record optional static gaps and save the assumptions with a real PDF, SVG, CSV or JSON report.
Wheel Geometry Studio
Choose your inputs, or load the working example to explore the result. Your files stay on this device.
Supported scope: Metric radial notation only, such as 225/45R17: width 125–445 mm, aspect 20–100%, rim diameter 10–30 in. Wheel bead-seat width 3–16 in; offset -100 to +150 mm; spacer 0–100 mm. Numeric bounds are parser limits, not approved equipment ranges. · No vehicle database or mounting approval. Actual tire profile, loaded radius, approved rim widths, load/speed ratings, bolt pattern, center bore, spoke/caliper shape, steering and suspension travel are not evaluated. Spacer input is dimensional arithmetic, not a recommendation. · Measured baseline gaps are optional static tire-envelope measurements in mm. Calculated candidate gaps use nominal dimensions and are not guarantees. No automatic storage; import/export this tool’s JSON up to 20 KB.
Your inputs
Required fields are marked with an asterisk.
Your result
Review your output, then save it to your device.
Make the next step clear.
Your findings, assumptions and next steps will appear here after you run the check.
Wheel Geometry Studio · https://wheels.kitforma.com/ · KitForma
Separate tire and wheel inner/outer changes
Measured-gap arithmetic with unknown values retained
Vector drawing and editable scenario exports
Understand the evidence.
Focused guides explain the rules, the edge cases and the checks worth doing before you act.
Read inner and outer movement without reversing the signs
Separate centerline shift, width change and the reference plane used by each number.
Read the guide ↗Field guide / 02Compare nominal tire diameter and speed ratio
Understand exactly what follows from a size code and what still needs measurement.
Read the guide ↗Field guide / 03Record static gaps and save a reproducible scenario
Use measured inputs carefully and preserve the assumptions with the diagram.
Read the guide ↗Before you start
Does a positive clearance estimate mean the setup fits?
No. It subtracts a nominal dimension change from a supplied static gap. Tire model, measuring rim, pressure, load, steering, suspension movement and obstruction shape can change the actual clearance. The tool does not inspect the vehicle, approved rim ranges or mounting requirements.
Why are tire and wheel movements different?
Wheel width is the nominal bead-seat width, converted from inches. Tire width is the nominal section width in the size code. The program positions both around the offset-adjusted centerline but calculates their edges separately. It does not add an invented rim-lip thickness or infer tire stretch.
What does positive ET or a spacer do in the drawing?
Positive offset moves the wheel center inboard relative to the hub mounting plane. Spacer thickness moves it outboard, so effective offset is ET minus spacer thickness. This is geometry only; entering a spacer does not establish that its hardware or installation is suitable.
Is the predicted speed the actual road speed?
It is a nominal ratio: indicated speed multiplied by candidate diameter divided by baseline diameter. It assumes the baseline speed calibration was exact and that nominal unloaded circumference represents rolling circumference. Neither assumption is measured here, so it is a comparison estimate rather than a calibration result.
Can I reopen or share a comparison?
Yes. Save the editable scenario JSON and import it later. PDF/SVG show the geometry, CSV contains the measurement table and calculation JSON includes unrounded numeric results. After editing offset or spacer in the result, prepare fresh files. No account or automatic storage is used.
Sources & assumptions
Formats, algorithms and supported features are documented below. Check the stated scope and inspect your output before using it.
- Michelin — How to read tire markings ↗
Primary explanation of nominal section width, aspect ratio and rim diameter. These codes do not supply an exact loaded tire envelope.
- Tire Rack — What is wheel offset? ↗
Primary wheel retailer explanation of mounting-face-to-centerline offset and its sign.
- Michelin — Choosing the right tire size ↗
Manufacturer context for consulting vehicle specifications and checking compatibility when dimensions change.
Reviewed 2026-10-19. Read our methodology or report an issue.