305/70R16 vs 255/80R17

255/80R17 is 0.25 in (6.4 mm) taller than 305/70R16, a +0.77% diameter difference. With the speedometer set for 305/70R16, an indicated 60 mph is 60.5 mph on 255/80R17.

Is this a safe swap?

Diameter difference +0.77%: under 1%

By overall diameter alone, 255/80R17 is a near match for 305/70R16; 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.

305/70R16 vs 255/80R17 differences
Measurement	305/70R16	255/80R17	Difference	% diff
Overall diameter	32.81 in (833.4 mm)	33.06 in (839.8 mm)	+0.25 in (+6.4 mm)	+0.77%
Sidewall height	8.41 in (213.5 mm)	8.03 in (204.0 mm)	−0.37 in (−9.5 mm)	−4.45%
Section width	12.01 in (305.0 mm)	10.04 in (255.0 mm)	−1.97 in (−50.0 mm)	−16.39%
Circumference	103.08 in (2,618.2 mm)	103.87 in (2,638.3 mm)	+0.79 in (+20.1 mm)	+0.77%
Revolutions per mile	615	610	−5	−0.76%

True speed with the speedometer calibrated for 305/70R16
Indicated	Actual on 305/70R16	Actual on 255/80R17	Difference
30 mph	30.0 mph	30.2 mph	+0.2 mph
60 mph	60.0 mph	60.5 mph	+0.5 mph
75 mph	75.0 mph	75.6 mph	+0.6 mph

Ride-height change: 255/80R17 raises the vehicle by 0.13 in (3.2 mm) at the axle (half the +6.4 mm diameter difference).

255/80R17 is 0.25 in taller than 305/70R16 and 50 mm narrower, a 0.77% difference in overall diameter.

With the speedometer calibrated for 305/70R16, an indicated 60 mph is actually 60.5 mph on 255/80R17, and revolutions per mile change from 615 to 610.

255/80R17 mounts on a 17-inch wheel, a plus-1 fitment from the 16-inch wheel of 305/70R16.

Size pages

Other comparisons with 305/70R16

Other comparisons with 255/80R17

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