TireSizesFinder

305/70R18 vs 295/60R20

295/60R20 is 0.87 in (22.2 mm) shorter than 305/70R18, a −2.51% diameter difference. With the speedometer set for 305/70R18, an indicated 60 mph is 58.5 mph on 295/60R20.

Is this a safe swap?

Diameter difference −2.51%: within the ±3% guideline

By overall diameter alone, 295/60R20 falls inside the ±3% range commonly used as a guideline when replacing 305/70R18. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 305/70R18 (34.81 in) vs 295/60R20 (33.94 in)305/70R1834.81 in × 12.01 in295/60R2033.94 in × 11.61 in
Side profile and tread width, drawn to the same scale.
305/70R18 vs 295/60R20 differences
Measurement305/70R18295/60R20Difference% diff
Overall diameter34.81 in (884.2 mm)33.94 in (862.0 mm)−0.87 in (−22.2 mm)−2.51%
Sidewall height8.41 in (213.5 mm)6.97 in (177.0 mm)−1.44 in (−36.5 mm)−17.10%
Section width12.01 in (305.0 mm)11.61 in (295.0 mm)−0.39 in (−10.0 mm)−3.28%
Circumference109.36 in (2,777.8 mm)106.62 in (2,708.1 mm)−2.75 in (−69.7 mm)−2.51%
Revolutions per mile579594+15+2.58%
True speed with the speedometer calibrated for 305/70R18
IndicatedActual on 305/70R18Actual on 295/60R20Difference
30 mph30.0 mph29.2 mph−0.8 mph
60 mph60.0 mph58.5 mph−1.5 mph
75 mph75.0 mph73.1 mph−1.9 mph

Ride-height change: 295/60R20 lowers the vehicle by 0.44 in (11.1 mm) at the axle (half the −22.2 mm diameter difference).

295/60R20 is 0.87 in shorter than 305/70R18 and 10 mm narrower, a 2.51% difference in overall diameter.

With the speedometer calibrated for 305/70R18, an indicated 60 mph is actually 58.5 mph on 295/60R20, and revolutions per mile change from 579 to 594.

295/60R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 305/70R18.

Size pages

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