235/70R17 vs 255/65R17

255/65R17 is 0.10 in (2.5 mm) taller than 235/70R17, a +0.33% diameter difference. With the speedometer set for 235/70R17, an indicated 60 mph is 60.2 mph on 255/65R17.

Is this a safe swap?

Diameter difference +0.33%: under 1%

By overall diameter alone, 255/65R17 is a near match for 235/70R17; 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.

235/70R17 vs 255/65R17 differences
Measurement	235/70R17	255/65R17	Difference	% diff
Overall diameter	29.95 in (760.8 mm)	30.05 in (763.3 mm)	+0.10 in (+2.5 mm)	+0.33%
Sidewall height	6.48 in (164.5 mm)	6.53 in (165.8 mm)	+0.05 in (+1.3 mm)	+0.76%
Section width	9.25 in (235.0 mm)	10.04 in (255.0 mm)	+0.79 in (+20.0 mm)	+8.51%
Circumference	94.10 in (2,390.1 mm)	94.41 in (2,398.0 mm)	+0.31 in (+7.9 mm)	+0.33%
Revolutions per mile	673	671	−2	−0.33%

True speed with the speedometer calibrated for 235/70R17
Indicated	Actual on 235/70R17	Actual on 255/65R17	Difference
30 mph	30.0 mph	30.1 mph	+0.1 mph
60 mph	60.0 mph	60.2 mph	+0.2 mph
75 mph	75.0 mph	75.2 mph	+0.2 mph

Ride-height change: 255/65R17 raises the vehicle by 0.05 in (1.3 mm) at the axle (half the +2.5 mm diameter difference).

255/65R17 is 0.10 in taller than 235/70R17 and 20 mm wider, a 0.33% difference in overall diameter.

With the speedometer calibrated for 235/70R17, an indicated 60 mph is actually 60.2 mph on 255/65R17, and revolutions per mile change from 673 to 671.

Both sizes mount on 17-inch wheels.

Size pages

Other comparisons with 235/70R17

Other comparisons with 255/65R17

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