235/85R16 vs 255/85R16

255/85R16 is 1.34 in (34.0 mm) taller than 235/85R16, a +4.22% diameter difference. With the speedometer set for 235/85R16, an indicated 60 mph is 62.5 mph on 255/85R16.

Is this a safe swap?

Diameter difference +4.22%: outside the ±3% guideline

By overall diameter alone, 255/85R16 falls outside the ±3% range commonly used as a guideline when replacing 235/85R16; speedometer and ride-height changes are larger. 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.

235/85R16 vs 255/85R16 differences
Measurement	235/85R16	255/85R16	Difference	% diff
Overall diameter	31.73 in (805.9 mm)	33.07 in (839.9 mm)	+1.34 in (+34.0 mm)	+4.22%
Sidewall height	7.86 in (199.8 mm)	8.53 in (216.8 mm)	+0.67 in (+17.0 mm)	+8.51%
Section width	9.25 in (235.0 mm)	10.04 in (255.0 mm)	+0.79 in (+20.0 mm)	+8.51%
Circumference	99.68 in (2,531.8 mm)	103.88 in (2,638.6 mm)	+4.21 in (+106.8 mm)	+4.22%
Revolutions per mile	636	610	−26	−4.05%

True speed with the speedometer calibrated for 235/85R16
Indicated	Actual on 235/85R16	Actual on 255/85R16	Difference
30 mph	30.0 mph	31.3 mph	+1.3 mph
60 mph	60.0 mph	62.5 mph	+2.5 mph
75 mph	75.0 mph	78.2 mph	+3.2 mph

Ride-height change: 255/85R16 raises the vehicle by 0.67 in (17.0 mm) at the axle (half the +34.0 mm diameter difference).

255/85R16 is 1.34 in taller than 235/85R16 and 20 mm wider, a 4.22% difference in overall diameter.

With the speedometer calibrated for 235/85R16, an indicated 60 mph is actually 62.5 mph on 255/85R16, and revolutions per mile change from 636 to 610.

Both sizes mount on 16-inch wheels.

Size pages

Other comparisons with 235/85R16

Other comparisons with 255/85R16

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