245/50R20 vs 275/45R20

275/45R20 is 0.10 in (2.5 mm) taller than 245/50R20, a +0.33% diameter difference. With the speedometer set for 245/50R20, an indicated 60 mph is 60.2 mph on 275/45R20.

Is this a safe swap?

Diameter difference +0.33%: under 1%

By overall diameter alone, 275/45R20 is a near match for 245/50R20; the speedometer changes by less than 1%. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

Side profile and tread width, drawn to the same scale.

245/50R20 vs 275/45R20 differences
Measurement	245/50R20	275/45R20	Difference	% diff
Overall diameter	29.65 in (753.0 mm)	29.74 in (755.5 mm)	+0.10 in (+2.5 mm)	+0.33%
Sidewall height	4.82 in (122.5 mm)	4.87 in (123.8 mm)	+0.05 in (+1.3 mm)	+1.02%
Section width	9.65 in (245.0 mm)	10.83 in (275.0 mm)	+1.18 in (+30.0 mm)	+12.24%
Circumference	93.13 in (2,365.6 mm)	93.44 in (2,373.5 mm)	+0.31 in (+7.9 mm)	+0.33%
Revolutions per mile	680	678	−2	−0.33%

True speed with the speedometer calibrated for 245/50R20
Indicated	Actual on 245/50R20	Actual on 275/45R20	Difference
30 mph	30.0 mph	30.1 mph	+0.1 mph
60 mph	60.0 mph	60.2 mph	+0.2 mph
75 mph	75.0 mph	75.2 mph	+0.2 mph

Ride-height change: 275/45R20 raises the vehicle by 0.05 in (1.3 mm) at the axle (half the +2.5 mm diameter difference).

275/45R20 is 0.10 in taller than 245/50R20 and 30 mm wider, a 0.33% difference in overall diameter.

With the speedometer calibrated for 245/50R20, an indicated 60 mph is actually 60.2 mph on 275/45R20, and revolutions per mile change from 680 to 678.

Both sizes mount on 20-inch wheels.

Size pages

Other comparisons with 245/50R20

Other comparisons with 275/45R20

Source: Calculated from standard tire geometry formulas. Verified 2026-09-27. How these numbers are calculated.