The Locolory toolkit / Automotive Fitment
Wheel Offset & Tire Size Fitment Calculator
Compare existing vs new wheel width and ET offset. Visualize inner strut clearance, fender poke, and speedometer calibration error.
Wheel Offset & Tire Size Fitment Calculator is a free browser-based utility that compare existing vs new wheel width and ET offset; Visualize inner strut clearance, fender poke, and speedometer calibration error.
- Core logic: compare wheel width and ET changes, then calculate inner clearance, outer poke, tire diameter, and speedometer variance.
No software download, login, or server upload required. Computations execute locally on device.
Wheel fitment comparison
● Calculated locally
Reads 65.0 mph · actual 66.9 mph (+3.0%)
Example shared platforms · 5x112
Volkswagen / Audi MQB, many Mercedes-Benz models, BMW G-series (selected models)
Center bore and fastener seat vary widely across platforms. Verify the exact year, trim, bore, hardware, and load rating.
Understanding Positive vs Negative ET Offset and Scrub Radius
ET offset measures the hub face relative to the rim centerline. Increasing positive ET pulls the wheel inward and increases backspacing; reducing ET pushes the outer lip toward the fender.
Offset also changes the tire contact patch relative to the steering axis, affecting scrub radius, steering effort, kickback, and bearing leverage. Similar inner and outer clearance does not guarantee acceptable steering geometry.
Fitment checks this calculator cannot see
Confirm hub center bore, bolt-seat type, thread pitch, brake-caliper barrel and spoke clearance, tire section width, load rating, and full-lock/full-bump clearance.
Published tire dimensions vary by manufacturer and approved rim width. Measure the actual assembly or use the tire maker's specification for a final decision.
Hardware reference
Common PCD Bolt Pattern Fitment Table
Example ranges only. Manufacturer compatibility varies by model, year, trim, bore, seat, and hardware.
| PCD | Typical thread examples | Common center bore (mm) | Manufacturer examples |
|---|---|---|---|
| 4×100 | M12×1.5 / varies | 54.1–57.1 | Honda, Mazda, Toyota, BMW examples |
| 5×100 | M12×1.25/1.5 | 54.1–57.1 | Subaru, Toyota, VW examples |
| 5×112 | M12/M14 · varies | 57.1–66.6 | VW/Audi, Mercedes, BMW examples |
| 5×114.3 | M12×1.25/1.5 | 56.1–67.1 | Honda, Toyota, Mazda, Hyundai examples |
| 5×120 | M12/M14 · varies | 64.1–72.6 | BMW, GM, Honda examples |
Your input shapes the next update
Spotted something? Tell us.
A short note opens in your email app, ready to send to hello@locolory.store.
Good questions. Clear answers.
What does ET offset mean on a wheel?
ET is the distance in millimeters from the wheel centerline to its hub-mounting face. Positive ET moves the wheel inward toward the suspension; lower or negative ET moves it outward toward the fender.
Will changing tire and wheel diameter make my speedometer inaccurate?
Yes. A larger rolling diameter travels farther per revolution, so actual road speed is higher than the indicated speed. A smaller diameter does the opposite. Tire wear, pressure, and real loaded radius also affect the final reading.
What happens if wheel offset is too high or too low?
Too much positive offset can reduce strut, control-arm, or brake clearance. Too little offset can cause fender contact and may change steering leverage, bearing load, and scrub radius. Check the full steering and suspension travel, not just static clearance.
Can I fit a 5x112 wheel on a 5x114.3 hub using wobble bolts?
Do not assume so. Wobble hardware is application-specific and cannot correct center-bore, seat profile, load rating, stud size, brake clearance, or offset problems. Use only hardware and adapters explicitly approved for the vehicle and wheel, and confirm legality and torque requirements with a qualified installer.