255/85R16 vs 305/65R17

305/65R17 is 0.46 in (11.6 mm) shorter than 255/85R16, a −1.38% diameter difference. With the speedometer set for 255/85R16, an indicated 60 mph is 59.2 mph on 305/65R17.

Is this a safe swap?

Diameter difference −1.38%: within the ±3% guideline

By overall diameter alone, 305/65R17 falls inside the ±3% range commonly used as a guideline when replacing 255/85R16. 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.

255/85R16 vs 305/65R17 differences
Measurement	255/85R16	305/65R17	Difference	% diff
Overall diameter	33.07 in (839.9 mm)	32.61 in (828.3 mm)	−0.46 in (−11.6 mm)	−1.38%
Sidewall height	8.53 in (216.8 mm)	7.81 in (198.3 mm)	−0.73 in (−18.5 mm)	−8.54%
Section width	10.04 in (255.0 mm)	12.01 in (305.0 mm)	+1.97 in (+50.0 mm)	+19.61%
Circumference	103.88 in (2,638.6 mm)	102.45 in (2,602.2 mm)	−1.43 in (−36.4 mm)	−1.38%
Revolutions per mile	610	618	+9	+1.40%

True speed with the speedometer calibrated for 255/85R16
Indicated	Actual on 255/85R16	Actual on 305/65R17	Difference
30 mph	30.0 mph	29.6 mph	−0.4 mph
60 mph	60.0 mph	59.2 mph	−0.8 mph
75 mph	75.0 mph	74.0 mph	−1.0 mph

Ride-height change: 305/65R17 lowers the vehicle by 0.23 in (5.8 mm) at the axle (half the −11.6 mm diameter difference).

305/65R17 is 0.46 in shorter than 255/85R16 and 50 mm wider, a 1.38% difference in overall diameter.

With the speedometer calibrated for 255/85R16, an indicated 60 mph is actually 59.2 mph on 305/65R17, and revolutions per mile change from 610 to 618.

305/65R17 mounts on a 17-inch wheel, a plus-1 fitment from the 16-inch wheel of 255/85R16.

Size pages

Other comparisons with 255/85R16

Other comparisons with 305/65R17

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