30x9.50R15 vs 255/70R16

255/70R16 is 0.06 in (1.4 mm) taller than 30x9.50R15, a +0.18% diameter difference. With the speedometer set for 30x9.50R15, an indicated 60 mph is 60.1 mph on 255/70R16.

Is this a safe swap?

Diameter difference +0.18%: under 1%

By overall diameter alone, 255/70R16 is a near match for 30x9.50R15; the speedometer changes by less than 1%. 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.

30x9.50R15 vs 255/70R16 differences
Measurement	30x9.50R15	255/70R16	Difference	% diff
Overall diameter	30.00 in (762.0 mm)	30.06 in (763.4 mm)	+0.06 in (+1.4 mm)	+0.18%
Sidewall height	7.50 in (190.5 mm)	7.03 in (178.5 mm)	−0.47 in (−12.0 mm)	−6.30%
Section width	9.50 in (241.3 mm)	10.04 in (255.0 mm)	+0.54 in (+13.7 mm)	+5.68%
Circumference	94.25 in (2,393.9 mm)	94.42 in (2,398.3 mm)	+0.17 in (+4.4 mm)	+0.18%
Revolutions per mile	672	671	−1	−0.18%

True speed with the speedometer calibrated for 30x9.50R15
Indicated	Actual on 30x9.50R15	Actual on 255/70R16	Difference
30 mph	30.0 mph	30.1 mph	+0.1 mph
60 mph	60.0 mph	60.1 mph	+0.1 mph
75 mph	75.0 mph	75.1 mph	+0.1 mph

Ride-height change: 255/70R16 raises the vehicle by 0.03 in (0.7 mm) at the axle (half the +1.4 mm diameter difference).

255/70R16 is 0.06 in taller than 30x9.50R15 and 14 mm wider, a 0.18% difference in overall diameter.

With the speedometer calibrated for 30x9.50R15, an indicated 60 mph is actually 60.1 mph on 255/70R16, and revolutions per mile change from 672 to 671.

255/70R16 mounts on a 16-inch wheel, a plus-1 fitment from the 15-inch wheel of 30x9.50R15.

Size pages

Other comparisons with 30x9.50R15

Other comparisons with 255/70R16

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