285/70R17 vs 255/80R17

255/80R17 is 0.35 in (9.0 mm) taller than 285/70R17, a +1.08% diameter difference. With the speedometer set for 285/70R17, an indicated 60 mph is 60.6 mph on 255/80R17.

Is this a safe swap?

Diameter difference +1.08%: within the ±3% guideline

By overall diameter alone, 255/80R17 falls inside the ±3% range commonly used as a guideline when replacing 285/70R17. 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.

285/70R17 vs 255/80R17 differences
Measurement	285/70R17	255/80R17	Difference	% diff
Overall diameter	32.71 in (830.8 mm)	33.06 in (839.8 mm)	+0.35 in (+9.0 mm)	+1.08%
Sidewall height	7.85 in (199.5 mm)	8.03 in (204.0 mm)	+0.18 in (+4.5 mm)	+2.26%
Section width	11.22 in (285.0 mm)	10.04 in (255.0 mm)	−1.18 in (−30.0 mm)	−10.53%
Circumference	102.76 in (2,610.0 mm)	103.87 in (2,638.3 mm)	+1.11 in (+28.3 mm)	+1.08%
Revolutions per mile	617	610	−7	−1.07%

True speed with the speedometer calibrated for 285/70R17
Indicated	Actual on 285/70R17	Actual on 255/80R17	Difference
30 mph	30.0 mph	30.3 mph	+0.3 mph
60 mph	60.0 mph	60.6 mph	+0.6 mph
75 mph	75.0 mph	75.8 mph	+0.8 mph

Ride-height change: 255/80R17 raises the vehicle by 0.18 in (4.5 mm) at the axle (half the +9.0 mm diameter difference).

255/80R17 is 0.35 in taller than 285/70R17 and 30 mm narrower, a 1.08% difference in overall diameter.

With the speedometer calibrated for 285/70R17, an indicated 60 mph is actually 60.6 mph on 255/80R17, and revolutions per mile change from 617 to 610.

Both sizes mount on 17-inch wheels.

Size pages

Other comparisons with 285/70R17

Other comparisons with 255/80R17

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