TireSizesFinder

235/55R20 vs 245/55R20

245/55R20 is 0.43 in (11.0 mm) taller than 235/55R20, a +1.44% diameter difference. With the speedometer set for 235/55R20, an indicated 60 mph is 60.9 mph on 245/55R20.

Is this a safe swap?

Diameter difference +1.44%: within the ±3% guideline

By overall diameter alone, 245/55R20 falls inside the ±3% range commonly used as a guideline when replacing 235/55R20. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 235/55R20 (30.18 in) vs 245/55R20 (30.61 in)235/55R2030.18 in × 9.25 in245/55R2030.61 in × 9.65 in
Side profile and tread width, drawn to the same scale.
235/55R20 vs 245/55R20 differences
Measurement235/55R20245/55R20Difference% diff
Overall diameter30.18 in (766.5 mm)30.61 in (777.5 mm)+0.43 in (+11.0 mm)+1.44%
Sidewall height5.09 in (129.3 mm)5.31 in (134.8 mm)+0.22 in (+5.5 mm)+4.26%
Section width9.25 in (235.0 mm)9.65 in (245.0 mm)+0.39 in (+10.0 mm)+4.26%
Circumference94.80 in (2,408.0 mm)96.16 in (2,442.6 mm)+1.36 in (+34.6 mm)+1.44%
Revolutions per mile668659−9−1.41%
True speed with the speedometer calibrated for 235/55R20
IndicatedActual on 235/55R20Actual on 245/55R20Difference
30 mph30.0 mph30.4 mph+0.4 mph
60 mph60.0 mph60.9 mph+0.9 mph
75 mph75.0 mph76.1 mph+1.1 mph

Ride-height change: 245/55R20 raises the vehicle by 0.22 in (5.5 mm) at the axle (half the +11.0 mm diameter difference).

245/55R20 is 0.43 in taller than 235/55R20 and 10 mm wider, a 1.44% difference in overall diameter.

With the speedometer calibrated for 235/55R20, an indicated 60 mph is actually 60.9 mph on 245/55R20, and revolutions per mile change from 668 to 659.

Both sizes mount on 20-inch wheels.

Size pages

Other comparisons with 235/55R20

Other comparisons with 245/55R20

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