Tire Size Calculator
Thinking about a wheel or tire change? Enter your current and new tire sizes to instantly see the diameter difference, sidewall change and how much your speedometer will be off.
Current tire
Width / Aspect R Diameter
New tire
Width / Aspect R Diameter
New diameter
653.2 mm
+18.9 mm
Difference
+2.98%
Within safe range
Ground clearance
+9.5 mm
ride height change
New sidewall
98.0 mm
45→40
Real speed @100
103.0
+3.0 km/h
✓ Under 3% diameter change — speedometer error is minimal and generally safe.
How tire size affects your car
A larger overall diameter raises your car and makes the speedometer read lower than your real speed; a smaller one does the opposite. Staying within about 3% of the original diameter keeps everything accurate. Width and aspect ratio also change the look and grip.
Want to see wheel styles on a real car before buying? Try the free demo →
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