245/65R18 vs 295/45R20

295/45R20 is 0.09 in (2.2 mm) shorter than 245/65R18, a −0.28% diameter difference. With the speedometer set for 245/65R18, an indicated 60 mph is 59.8 mph on 295/45R20.

Is this a safe swap?

Diameter difference −0.28%: under 1%

By overall diameter alone, 295/45R20 is a near match for 245/65R18; 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.

245/65R18 vs 295/45R20 differences
Measurement	245/65R18	295/45R20	Difference	% diff
Overall diameter	30.54 in (775.7 mm)	30.45 in (773.5 mm)	−0.09 in (−2.2 mm)	−0.28%
Sidewall height	6.27 in (159.3 mm)	5.23 in (132.8 mm)	−1.04 in (−26.5 mm)	−16.64%
Section width	9.65 in (245.0 mm)	11.61 in (295.0 mm)	+1.97 in (+50.0 mm)	+20.41%
Circumference	95.94 in (2,436.9 mm)	95.67 in (2,430.0 mm)	−0.27 in (−6.9 mm)	−0.28%
Revolutions per mile	660	662	+2	+0.28%

True speed with the speedometer calibrated for 245/65R18
Indicated	Actual on 245/65R18	Actual on 295/45R20	Difference
30 mph	30.0 mph	29.9 mph	−0.1 mph
60 mph	60.0 mph	59.8 mph	−0.2 mph
75 mph	75.0 mph	74.8 mph	−0.2 mph

Ride-height change: 295/45R20 lowers the vehicle by 0.04 in (1.1 mm) at the axle (half the −2.2 mm diameter difference).

295/45R20 is 0.09 in shorter than 245/65R18 and 50 mm wider, a 0.28% difference in overall diameter.

With the speedometer calibrated for 245/65R18, an indicated 60 mph is actually 59.8 mph on 295/45R20, and revolutions per mile change from 660 to 662.

295/45R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 245/65R18.

Size pages

Other comparisons with 245/65R18

Other comparisons with 295/45R20

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