275/70R18 vs 295/55R20

295/55R20 is 0.38 in (9.7 mm) shorter than 275/70R18, a −1.15% diameter difference. With the speedometer set for 275/70R18, an indicated 60 mph is 59.3 mph on 295/55R20.

Is this a safe swap?

Diameter difference −1.15%: within the ±3% guideline

By overall diameter alone, 295/55R20 falls inside the ±3% range commonly used as a guideline when replacing 275/70R18. 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.

275/70R18 vs 295/55R20 differences
Measurement	275/70R18	295/55R20	Difference	% diff
Overall diameter	33.16 in (842.2 mm)	32.78 in (832.5 mm)	−0.38 in (−9.7 mm)	−1.15%
Sidewall height	7.58 in (192.5 mm)	6.39 in (162.3 mm)	−1.19 in (−30.2 mm)	−15.71%
Section width	10.83 in (275.0 mm)	11.61 in (295.0 mm)	+0.79 in (+20.0 mm)	+7.27%
Circumference	104.17 in (2,645.8 mm)	102.97 in (2,615.4 mm)	−1.20 in (−30.5 mm)	−1.15%
Revolutions per mile	608	615	+7	+1.17%

True speed with the speedometer calibrated for 275/70R18
Indicated	Actual on 275/70R18	Actual on 295/55R20	Difference
30 mph	30.0 mph	29.7 mph	−0.3 mph
60 mph	60.0 mph	59.3 mph	−0.7 mph
75 mph	75.0 mph	74.1 mph	−0.9 mph

Ride-height change: 295/55R20 lowers the vehicle by 0.19 in (4.9 mm) at the axle (half the −9.7 mm diameter difference).

295/55R20 is 0.38 in shorter than 275/70R18 and 20 mm wider, a 1.15% difference in overall diameter.

With the speedometer calibrated for 275/70R18, an indicated 60 mph is actually 59.3 mph on 295/55R20, and revolutions per mile change from 608 to 615.

295/55R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 275/70R18.

Size pages

Other comparisons with 275/70R18

Other comparisons with 295/55R20

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