TireSizesFinder

225/50R18 vs 245/35R20

245/35R20 is 0.11 in (2.7 mm) shorter than 225/50R18, a −0.40% diameter difference. With the speedometer set for 225/50R18, an indicated 60 mph is 59.8 mph on 245/35R20.

Is this a safe swap?

Diameter difference −0.40%: under 1%

By overall diameter alone, 245/35R20 is a near match for 225/50R18; the speedometer changes by less than 1%. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 225/50R18 (26.86 in) vs 245/35R20 (26.75 in)225/50R1826.86 in × 8.86 in245/35R2026.75 in × 9.65 in
Side profile and tread width, drawn to the same scale.
225/50R18 vs 245/35R20 differences
Measurement225/50R18245/35R20Difference% diff
Overall diameter26.86 in (682.2 mm)26.75 in (679.5 mm)−0.11 in (−2.7 mm)−0.40%
Sidewall height4.43 in (112.5 mm)3.38 in (85.8 mm)−1.05 in (−26.7 mm)−23.78%
Section width8.86 in (225.0 mm)9.65 in (245.0 mm)+0.79 in (+20.0 mm)+8.89%
Circumference84.38 in (2,143.2 mm)84.04 in (2,134.7 mm)−0.33 in (−8.5 mm)−0.40%
Revolutions per mile751754+3+0.40%
True speed with the speedometer calibrated for 225/50R18
IndicatedActual on 225/50R18Actual on 245/35R20Difference
30 mph30.0 mph29.9 mph−0.1 mph
60 mph60.0 mph59.8 mph−0.2 mph
75 mph75.0 mph74.7 mph−0.3 mph

Ride-height change: 245/35R20 lowers the vehicle by 0.05 in (1.4 mm) at the axle (half the −2.7 mm diameter difference).

245/35R20 is 0.11 in shorter than 225/50R18 and 20 mm wider, a 0.40% difference in overall diameter.

With the speedometer calibrated for 225/50R18, an indicated 60 mph is actually 59.8 mph on 245/35R20, and revolutions per mile change from 751 to 754.

245/35R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 225/50R18.

Size pages

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Source: Calculated from standard tire geometry formulas. Verified . How these numbers are calculated.