US Dollars
Wheel Backspace Offset Calculator & Visualizer
Use our wheel backspace offset calculator to compare your current wheels and tires with a new setup. See inner clearance (suspension side), outer position (fender side), and how offset and backspacing change—before you buy.
Key Features
- Side-by-side comparison of current vs. desired wheel/tire setups (metric or imperial).
- Automatic offset and backspacing calculations.
- Visualize inner clearance and fender poke changes.
- See front and rear configurations independently.
- Generate alternative rim and tire sizes.
- Adjust for fender, strut, and wheel-well clearances.
Enter your wheels and tires configuration in one panel, and your desired configuration in the other.
How to Use the Calculator
- Measure wheel width correctly. Most rims have the diameter, the width, and the offset stamped on the back of the wheel. The drawback is that you have to remove the rim from the vehicle to read it. The alternative is to measure the rim width yourself.
Labeled wheel width is measured bead seat to bead seat (between inner flanges), not lip-to-lip. - Enter current and desired specs. Input wheel width, diameter, and offset for both setups; add tire sizes if you want overall diameter changes.
- Review results. Check inner clearance vs. suspension and outer position vs. fender. Confirm there’s no rubbing throughout suspension travel and steering lock.
Tip: Overall wheel width is typically ~1.0 in greater than the labeled (bead) width because of the rim flanges. Some designs vary—measure if in doubt.
Wheel Offset Explained
Offset is the distance (mm) between the hub mounting surface and the wheel’s centerline.
- Positive offset (ET +): Hub pad is toward the outside face. Common on OEM wheels, the wheel sits further inboard and may limit tire width if excessive.
- Negative offset (ET –): Hub pad is toward the inner lip. Pushes wheels outward for a wider stance—useful for some trucks/off-road builds—but may increase bearing loads and require fender coverage.
- Zero offset: Hub pad lies on the centerline.
Offset vs. Backspacing
Backspacing is the distance (in inches) from the hub mounting surface to the inner rim edge of the wheel. It’s commonly measured with a straightedge and a ruler.
Using the common 1.0" overall-width convention:
Offset (mm) = [Backspacing (in) − ((Wheel Width (in) + 1) ÷ 2)] × 25.4
Backspacing (in) = ((Wheel Width (in) + 1) ÷ 2) + [Offset (mm) ÷ 25.4]
Examples:
- 8.0" wheel, zero offset → Backspacing ≈ ((8.0 + 1)/2) = 4.5".
- 8.0" wheel, 5.0" backspacing → Offset = (5.0 − 4.5) × 25.4 = +12.7 mm.
- 8.0" wheel, 4.0" backspacing → Offset = (4.0 − 4.5) × 25.4 = −12.7 mm.
Choosing the Right Offset
- Too much positive offset: The wheel is inset, and it may rub; it can also reduce inner clearance and contact struts or brakes.
- Too much negative offset: The wheel is poking out, not flush to the vehicle's body. Greta for wide stances, but may increase fender poke and can raise loads on bearings and ball joints.
- Balanced offset: Preserves handling, tire wear, and component life while achieving the stance you want.
Always check both sides—fender and suspension—and consider suspension travel and steering lock. Local regulations may require tire tread to be covered by fenders/flares.
Practical Example
Stock: 17 × 7.5J, ET +45
New: 18 × 8.5J, ET +35
- Outer position change (poke): +22.7 mm (≈ 0.89") outward.
- Inner position change (clearance): inner edge moves +2.7 mm (≈ 0.11") toward the suspension (i.e., reduces inner clearance by 2.7 mm).
Use the calculator above to confirm changes for your exact specs and tires.
Wheel Backspace Offset Calculator – Try It
Enter your current and desired wheel/tire sizes to visualize inner clearance and fender poke.
Related Resources
Here are a few tech articles you may want to read for further research
What is the Infiniti Q50 bolt pattern and offset?
The Infiniti Q50 uses a 5x114.3 bolt pattern across all model years. Offset ranges from +45mm to +50mm depending on wheel size. Stock 19-inch wheels typically run +50mm offset for optimal handling and clearance. Here is a guide with the Infiniti wheel specs:
| Wheel Size | Bolt Pattern | Offset | OEM Tire |
|---|---|---|---|
| 17x7.5" | 5x114.3 (4.5") | +45 | 225/55ZR17 97W |
| 18x7.5" | 5x114.3 (4.5") | +45 | 225/50ZR18 95W |
| 19x8.5" | 5x114.3 (4.5") | +50 | 245/40ZR19 94W |
| 19x9" Front | 5x114.3 (4.5") | +47 | 245/40ZR19 94W |
| 19x9.5" Rear | 5x114.3 (4.5") | +50 | 265/35ZR19 94W |
How can I tell if an Infiniti rim is OEM vs replica?
Genuine OEM wheels have the Infiniti logo and a part number cast on the back of the wheel. Weight and finish quality may also differ.
Do 20-inch wheels fit the Infiniti QX50 without rubbing?
20-inch wheels can fit QX50 models with proper offset and tire sizing. Lower tire profile (e.g., 245/35R20 or 275/30R20) helps avoid fender work. The QX50 ships with 19-inch wheels from the factory.
Are PVD black chrome finishes durable on Infiniti OEM wheels?
PVD finishes resist corrosion and keep their shine with proper care. Curb rash usually needs refinishing or replacement. High-gloss black (powder coat) is a lower-cost alternative that’s easier to repair.