255/45R19 vs 295/30R21

295/30R21 is 0.07 in (1.7 mm) shorter than 255/45R19, a −0.24% diameter difference. With the speedometer set for 255/45R19, an indicated 60 mph is 59.9 mph on 295/30R21.

Is this a safe swap?

Diameter difference −0.24%: under 1%

By overall diameter alone, 295/30R21 is a near match for 255/45R19; 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.

255/45R19 vs 295/30R21 differences
Measurement	255/45R19	295/30R21	Difference	% diff
Overall diameter	28.04 in (712.1 mm)	27.97 in (710.4 mm)	−0.07 in (−1.7 mm)	−0.24%
Sidewall height	4.52 in (114.8 mm)	3.48 in (88.5 mm)	−1.03 in (−26.2 mm)	−22.88%
Section width	10.04 in (255.0 mm)	11.61 in (295.0 mm)	+1.57 in (+40.0 mm)	+15.69%
Circumference	88.08 in (2,237.1 mm)	87.87 in (2,231.8 mm)	−0.21 in (−5.3 mm)	−0.24%
Revolutions per mile	719	721	+2	+0.24%

True speed with the speedometer calibrated for 255/45R19
Indicated	Actual on 255/45R19	Actual on 295/30R21	Difference
30 mph	30.0 mph	29.9 mph	−0.1 mph
60 mph	60.0 mph	59.9 mph	−0.1 mph
75 mph	75.0 mph	74.8 mph	−0.2 mph

Ride-height change: 295/30R21 lowers the vehicle by 0.03 in (0.8 mm) at the axle (half the −1.7 mm diameter difference).

295/30R21 is 0.07 in shorter than 255/45R19 and 40 mm wider, a 0.24% difference in overall diameter.

With the speedometer calibrated for 255/45R19, an indicated 60 mph is actually 59.9 mph on 295/30R21, and revolutions per mile change from 719 to 721.

295/30R21 mounts on a 21-inch wheel, a plus-2 fitment from the 19-inch wheel of 255/45R19.

Size pages

Other comparisons with 255/45R19

Other comparisons with 295/30R21

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