TireSizesFinder

295/45R20 vs 295/40R21

295/40R21 is 0.16 in (4.1 mm) shorter than 295/45R20, a −0.53% diameter difference. With the speedometer set for 295/45R20, an indicated 60 mph is 59.7 mph on 295/40R21.

Is this a safe swap?

Diameter difference −0.53%: under 1%

By overall diameter alone, 295/40R21 is a near match for 295/45R20; the speedometer changes by less than 1%. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 295/45R20 (30.45 in) vs 295/40R21 (30.29 in)295/45R2030.45 in × 11.61 in295/40R2130.29 in × 11.61 in
Side profile and tread width, drawn to the same scale.
295/45R20 vs 295/40R21 differences
Measurement295/45R20295/40R21Difference% diff
Overall diameter30.45 in (773.5 mm)30.29 in (769.4 mm)−0.16 in (−4.1 mm)−0.53%
Sidewall height5.23 in (132.8 mm)4.65 in (118.0 mm)−0.58 in (−14.7 mm)−11.11%
Section width11.61 in (295.0 mm)11.61 in (295.0 mm)0.00 in (0.0 mm)0.00%
Circumference95.67 in (2,430.0 mm)95.16 in (2,417.1 mm)−0.51 in (−12.9 mm)−0.53%
Revolutions per mile662666+4+0.53%
True speed with the speedometer calibrated for 295/45R20
IndicatedActual on 295/45R20Actual on 295/40R21Difference
30 mph30.0 mph29.8 mph−0.2 mph
60 mph60.0 mph59.7 mph−0.3 mph
75 mph75.0 mph74.6 mph−0.4 mph

Ride-height change: 295/40R21 lowers the vehicle by 0.08 in (2.1 mm) at the axle (half the −4.1 mm diameter difference).

295/40R21 is 0.16 in shorter than 295/45R20 and the same width, a 0.53% difference in overall diameter.

With the speedometer calibrated for 295/45R20, an indicated 60 mph is actually 59.7 mph on 295/40R21, and revolutions per mile change from 662 to 666.

295/40R21 mounts on a 21-inch wheel, a plus-1 fitment from the 20-inch wheel of 295/45R20.

Size pages

Other comparisons with 295/45R20

Other comparisons with 295/40R21

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