TireSizesFinder

285/40R18 vs 295/30R20

295/30R20 is 0.01 in (0.2 mm) shorter than 285/40R18, a −0.03% diameter difference. With the speedometer set for 285/40R18, an indicated 60 mph is 60.0 mph on 295/30R20.

Is this a safe swap?

Diameter difference −0.03%: under 1%

By overall diameter alone, 295/30R20 is a near match for 285/40R18; 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: 285/40R18 (26.98 in) vs 295/30R20 (26.97 in)285/40R1826.98 in × 11.22 in295/30R2026.97 in × 11.61 in
Side profile and tread width, drawn to the same scale.
285/40R18 vs 295/30R20 differences
Measurement285/40R18295/30R20Difference% diff
Overall diameter26.98 in (685.2 mm)26.97 in (685.0 mm)−0.01 in (−0.2 mm)−0.03%
Sidewall height4.49 in (114.0 mm)3.48 in (88.5 mm)−1.00 in (−25.5 mm)−22.37%
Section width11.22 in (285.0 mm)11.61 in (295.0 mm)+0.39 in (+10.0 mm)+3.51%
Circumference84.75 in (2,152.6 mm)84.72 in (2,152.0 mm)−0.02 in (−0.6 mm)−0.03%
Revolutions per mile7487480+0.03%
True speed with the speedometer calibrated for 285/40R18
IndicatedActual on 285/40R18Actual on 295/30R20Difference
30 mph30.0 mph30.0 mph0.0 mph
60 mph60.0 mph60.0 mph0.0 mph
75 mph75.0 mph75.0 mph0.0 mph

Ride-height change: 295/30R20 lowers the vehicle by 0.00 in (0.1 mm) at the axle (half the −0.2 mm diameter difference).

295/30R20 is 0.01 in shorter than 285/40R18 and 10 mm wider, a 0.03% difference in overall diameter.

With the speedometer calibrated for 285/40R18, an indicated 60 mph is actually 60.0 mph on 295/30R20, and revolutions per mile change from 748 to 748.

295/30R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 285/40R18.

Size pages

Other comparisons with 285/40R18

Other comparisons with 295/30R20

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