Wheeldelta: Tire Fitment

Wheeldelta compares your current tire and wheel setup with a new one and shows how the change affects overall diameter, your speedometer reading, and where the tire sits in the wheel well.

ENTER BOTH SETUPS
For the current and the new setup, enter tire width (mm), aspect ratio (%), rim diameter (inches) and wheel offset (mm), plus a speedometer reading. The results update as you type.

WHAT IT CALCULATES
- Diameter change: the percentage difference in overall tire diameter, using rim diameter plus twice the sidewall height
- Actual speed: your true speed when the speedometer shows the reading you entered, for a speedometer matched to the current setup
- Inner change: how far the inner edge moves toward the suspension (positive) or away from it (negative), in millimeters, from the change in width and offset
- Outer change: how far the outer edge moves out toward the fender (positive) or in (negative), in millimeters
- Share calculation: sends a text summary with both overall diameters, every result above, and the engine RPM change at the same road speed

EXAMPLE
Going from 225/45R17 at +45 mm offset to 245/40R18 at +38 mm: the overall diameter grows 2.98%, a 65 mph speedometer reading is really about 66.9 mph, the inner edge moves 3 mm closer to the suspension and the outer edge sits 17 mm further out.

GOOD TO KNOW
Wheeldelta uses nominal tire sizes and the tire's section width for the position estimate. Real dimensions vary by brand and rim width, and Wheeldelta does not measure brake, strut or fender clearance. Treat the results as a starting estimate and confirm fitment with your tire shop or vehicle manufacturer.

PRIVACY
All calculations stay on your device. No account, no ads and no analytics.