235/80R17 vs 255/75R17

255/75R17 is 0.26 in (6.5 mm) taller than 235/80R17, a +0.80% diameter difference. With the speedometer set for 235/80R17, an indicated 60 mph is 60.5 mph on 255/75R17.

Is this a safe swap?

Diameter difference +0.80%: under 1%

By overall diameter alone, 255/75R17 is a near match for 235/80R17; 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.

235/80R17 vs 255/75R17 differences
Measurement	235/80R17	255/75R17	Difference	% diff
Overall diameter	31.80 in (807.8 mm)	32.06 in (814.3 mm)	+0.26 in (+6.5 mm)	+0.80%
Sidewall height	7.40 in (188.0 mm)	7.53 in (191.3 mm)	+0.13 in (+3.3 mm)	+1.73%
Section width	9.25 in (235.0 mm)	10.04 in (255.0 mm)	+0.79 in (+20.0 mm)	+8.51%
Circumference	99.91 in (2,537.8 mm)	100.72 in (2,558.2 mm)	+0.80 in (+20.4 mm)	+0.80%
Revolutions per mile	634	629	−5	−0.80%

True speed with the speedometer calibrated for 235/80R17
Indicated	Actual on 235/80R17	Actual on 255/75R17	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: 255/75R17 raises the vehicle by 0.13 in (3.3 mm) at the axle (half the +6.5 mm diameter difference).

255/75R17 is 0.26 in taller than 235/80R17 and 20 mm wider, a 0.80% difference in overall diameter.

With the speedometer calibrated for 235/80R17, an indicated 60 mph is actually 60.5 mph on 255/75R17, and revolutions per mile change from 634 to 629.

Both sizes mount on 17-inch wheels.

Size pages

Other comparisons with 235/80R17

Other comparisons with 255/75R17

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