Wheel & Tire Clearance Estimator
Plan your fitment — estimate inner clearance and outer poke before you buy.
REAL-WORLD EXAMPLE
You’re planning to install 18x9.5" wheels with +35mm offset and 255/40R18 tires on a car that currently runs 18x8.5" +45mm wheels with 235/45R18 tires. Compared with your current setup, the new wheels and tires will sit noticeably further out toward the fender and the inner barrel will move closer to the strut and control arms. Use the calculator below to estimate roughly how many millimetres or inches of outer “poke” you gain and how much inner clearance you lose so you can judge whether rubbing or contact is likely.
Original Setup
Diameter: 24.97" · Sidewall: 101.3mm
New Setup
Diameter: 25.33" · Sidewall: 105.8mm
Diameter Change
+9.0mm
+0.35"
Width Change
+10mm
Wider
Offset Delta
+3mm
More positive
Sidewall Change
+4.5mm
height delta
Inner Clearance (suspension side)
Reduced by 2.0mm (0.08") — less space to suspension
Outer Position (fender side)
8.0mm (0.31") more poke — wheel moves outward
These are geometric estimates based on straight-line math. Actual clearance depends on suspension geometry, steering lock angle, and body tolerances. Always physically verify fitment after installation, especially under full suspension droop/compression and full steering lock.
AI Insight
Powered by AIGet a plain-English explanation of your results — what they mean for your vehicle and driving experience.
Common Fitment Clearance Changes
| Change | Effect on Outer Position | Effect on Inner Clearance |
|---|---|---|
| Wheel width +1" (same offset) | Outer lip moves ~0.5" outward | Inner barrel moves ~0.5" closer to suspension |
| Offset −10mm (same width) | Wheel and tire move ~0.39" outward | Inner clearance reduced by ~0.39" |
| Offset +10mm (same width) | Wheel and tire move ~0.39" inward | Inner clearance increased by ~0.39", less poke |
| Tire width +20mm (same wheel) | Sidewall extends ≈10mm further outward (and ~10mm inward) | Small inner clearance loss; shape depends on tire model |
Values above are approximate static changes relative to your current setup, assuming the same tire model and alignment. Real-world clearance also depends on camber, ride height, suspension travel, and tire shape.
How to Use This Estimator
- Measure or look up your current wheel and tire specs (width, offset, and tire size).
- Enter your current wheel width and offset, then enter the proposed new wheel width and offset, plus tire sizes if available.
- Click 'Estimate Clearance'.
- Review the calculated change in inner clearance (toward the suspension) and outer position (poke relative to the fender).
- Use the results and visual diagram as a starting point, then test clearance on the actual vehicle at full lock and with the suspension compressed before finalizing your setup.
Clearance Calculation Explained
About Wheel & Tire Clearance
Inner vs Outer Clearance: What You’re Balancing
Inner clearance is the gap between your wheel/tire and suspension parts like struts, shocks, control arms, and brake components. Outer clearance (or poke) describes how far the wheel and tire sit relative to the fender and bumper. Moving a wheel outward usually improves inner clearance but increases poke and rubbing risk on the body; moving it inward does the opposite, protecting the fender while reducing space near the suspension.
Key Factors That Affect Clearance
- Wheel width: Wider wheels add width on both the inner and outer sides relative to the hub.
- Offset (ET): Lower or more negative offset pushes the wheel out; higher positive offset pulls it inward.
- Tire size and profile: Wider and/or taller tires fill more of the wheel well and can hit liners or fenders under compression.
- Alignment and ride height: Camber, toe, lowering springs, coilovers, and spacers all change where the tire sits as the suspension moves.
Pro Tips for Planning Fitment
Use this estimator to compare your current setup to a proposed one before you buy, then test-fit one wheel on the car and check clearance with the steering at full lock and the suspension compressed (or as close as you can safely simulate). If you are pushing into aggressive fitment or stance territory, plan on supporting mods such as camber adjustment, fender rolling, trimming plastics, or adding flares, and always keep safety and local regulations in mind when choosing how much poke is acceptable.