295/70R18 vs 315/60R20

315/60R20 is 0.62 in (15.8 mm) taller than 295/70R18, a +1.82% diameter difference. With the speedometer set for 295/70R18, an indicated 60 mph is 61.1 mph on 315/60R20.

Is this a safe swap?

Diameter difference +1.82%: within the ±3% guideline

By overall diameter alone, 315/60R20 falls inside the ±3% range commonly used as a guideline when replacing 295/70R18. 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.

295/70R18 vs 315/60R20 differences
Measurement	295/70R18	315/60R20	Difference	% diff
Overall diameter	34.26 in (870.2 mm)	34.88 in (886.0 mm)	+0.62 in (+15.8 mm)	+1.82%
Sidewall height	8.13 in (206.5 mm)	7.44 in (189.0 mm)	−0.69 in (−17.5 mm)	−8.47%
Section width	11.61 in (295.0 mm)	12.40 in (315.0 mm)	+0.79 in (+20.0 mm)	+6.78%
Circumference	107.63 in (2,733.8 mm)	109.58 in (2,783.5 mm)	+1.95 in (+49.6 mm)	+1.82%
Revolutions per mile	589	578	−10	−1.78%

True speed with the speedometer calibrated for 295/70R18
Indicated	Actual on 295/70R18	Actual on 315/60R20	Difference
30 mph	30.0 mph	30.5 mph	+0.5 mph
60 mph	60.0 mph	61.1 mph	+1.1 mph
75 mph	75.0 mph	76.4 mph	+1.4 mph

Ride-height change: 315/60R20 raises the vehicle by 0.31 in (7.9 mm) at the axle (half the +15.8 mm diameter difference).

315/60R20 is 0.62 in taller than 295/70R18 and 20 mm wider, a 1.82% difference in overall diameter.

With the speedometer calibrated for 295/70R18, an indicated 60 mph is actually 61.1 mph on 315/60R20, and revolutions per mile change from 589 to 578.

315/60R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 295/70R18.

Size pages

Other comparisons with 295/70R18

Other comparisons with 315/60R20

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