265/55R19 vs 305/45R20

305/45R20 is 0.33 in (8.4 mm) taller than 265/55R19, a +1.09% diameter difference. With the speedometer set for 265/55R19, an indicated 60 mph is 60.7 mph on 305/45R20.

Is this a safe swap?

Diameter difference +1.09%: within the ±3% guideline

By overall diameter alone, 305/45R20 falls inside the ±3% range commonly used as a guideline when replacing 265/55R19. 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.

265/55R19 vs 305/45R20 differences
Measurement	265/55R19	305/45R20	Difference	% diff
Overall diameter	30.48 in (774.1 mm)	30.81 in (782.5 mm)	+0.33 in (+8.4 mm)	+1.09%
Sidewall height	5.74 in (145.8 mm)	5.40 in (137.3 mm)	−0.33 in (−8.5 mm)	−5.83%
Section width	10.43 in (265.0 mm)	12.01 in (305.0 mm)	+1.57 in (+40.0 mm)	+15.09%
Circumference	95.74 in (2,431.9 mm)	96.78 in (2,458.3 mm)	+1.04 in (+26.4 mm)	+1.09%
Revolutions per mile	662	655	−7	−1.07%

True speed with the speedometer calibrated for 265/55R19
Indicated	Actual on 265/55R19	Actual on 305/45R20	Difference
30 mph	30.0 mph	30.3 mph	+0.3 mph
60 mph	60.0 mph	60.7 mph	+0.7 mph
75 mph	75.0 mph	75.8 mph	+0.8 mph

Ride-height change: 305/45R20 raises the vehicle by 0.17 in (4.2 mm) at the axle (half the +8.4 mm diameter difference).

305/45R20 is 0.33 in taller than 265/55R19 and 40 mm wider, a 1.09% difference in overall diameter.

With the speedometer calibrated for 265/55R19, an indicated 60 mph is actually 60.7 mph on 305/45R20, and revolutions per mile change from 662 to 655.

305/45R20 mounts on a 20-inch wheel, a plus-1 fitment from the 19-inch wheel of 265/55R19.

Size pages

Other comparisons with 265/55R19

Other comparisons with 305/45R20

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