Plus Sizing Calculator
Going from 17s to 20s? The trick is a lower-profile tire so the overall diameter stays the same — otherwise your speedometer, gearing and ABS are off. Enter your current tire and the new wheel size.
Diameter is only one constraint. A plus-sized tire is usually
wider and always on a bigger wheel — check clearance
and rim width too. Stay within ±3% unless
you're recalibrating the speedometer.
Rules of thumb
- +1 inch of wheel ≈ −10 aspect points at similar width (265/70R17 → 265/60R18 → 265/50R19). The tool does the exact math.
- Positive deviation means a taller tire: speedometer reads low, effective gearing gets taller. Negative is the reverse.
- Going wider adds sidewall height for the same aspect, so a wider plus-size often wants a slightly lower aspect ratio.