245/70R17 vs 255/70R17

255/70R17 is 0.55 in (14.0 mm) taller than 245/70R17, a +1.81% diameter difference. With the speedometer set for 245/70R17, an indicated 60 mph is 61.1 mph on 255/70R17.

Is this a safe swap?

Diameter difference +1.81%: within the ±3% guideline

By overall diameter alone, 255/70R17 falls inside the ±3% range commonly used as a guideline when replacing 245/70R17. 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.

245/70R17 vs 255/70R17 differences
Measurement	245/70R17	255/70R17	Difference	% diff
Overall diameter	30.50 in (774.8 mm)	31.06 in (788.8 mm)	+0.55 in (+14.0 mm)	+1.81%
Sidewall height	6.75 in (171.5 mm)	7.03 in (178.5 mm)	+0.28 in (+7.0 mm)	+4.08%
Section width	9.65 in (245.0 mm)	10.04 in (255.0 mm)	+0.39 in (+10.0 mm)	+4.08%
Circumference	95.83 in (2,434.1 mm)	97.56 in (2,478.1 mm)	+1.73 in (+44.0 mm)	+1.81%
Revolutions per mile	661	649	−12	−1.77%

True speed with the speedometer calibrated for 245/70R17
Indicated	Actual on 245/70R17	Actual on 255/70R17	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: 255/70R17 raises the vehicle by 0.28 in (7.0 mm) at the axle (half the +14.0 mm diameter difference).

255/70R17 is 0.55 in taller than 245/70R17 and 10 mm wider, a 1.81% difference in overall diameter.

With the speedometer calibrated for 245/70R17, an indicated 60 mph is actually 61.1 mph on 255/70R17, and revolutions per mile change from 661 to 649.

Both sizes mount on 17-inch wheels.

Size pages

Other comparisons with 245/70R17

Other comparisons with 255/70R17

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