245/65R16 vs 285/45R18

285/45R18 is 0.44 in (11.2 mm) shorter than 245/65R16, a −1.55% diameter difference. With the speedometer set for 245/65R16, an indicated 60 mph is 59.1 mph on 285/45R18.

Is this a safe swap?

Diameter difference −1.55%: within the ±3% guideline

By overall diameter alone, 285/45R18 falls inside the ±3% range commonly used as a guideline when replacing 245/65R16. 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.

245/65R16 vs 285/45R18 differences
Measurement	245/65R16	285/45R18	Difference	% diff
Overall diameter	28.54 in (724.9 mm)	28.10 in (713.7 mm)	−0.44 in (−11.2 mm)	−1.55%
Sidewall height	6.27 in (159.3 mm)	5.05 in (128.3 mm)	−1.22 in (−31.0 mm)	−19.47%
Section width	9.65 in (245.0 mm)	11.22 in (285.0 mm)	+1.57 in (+40.0 mm)	+16.33%
Circumference	89.66 in (2,277.3 mm)	88.27 in (2,242.2 mm)	−1.39 in (−35.2 mm)	−1.55%
Revolutions per mile	707	718	+11	+1.57%

True speed with the speedometer calibrated for 245/65R16
Indicated	Actual on 245/65R16	Actual on 285/45R18	Difference
30 mph	30.0 mph	29.5 mph	−0.5 mph
60 mph	60.0 mph	59.1 mph	−0.9 mph
75 mph	75.0 mph	73.8 mph	−1.2 mph

Ride-height change: 285/45R18 lowers the vehicle by 0.22 in (5.6 mm) at the axle (half the −11.2 mm diameter difference).

285/45R18 is 0.44 in shorter than 245/65R16 and 40 mm wider, a 1.55% difference in overall diameter.

With the speedometer calibrated for 245/65R16, an indicated 60 mph is actually 59.1 mph on 285/45R18, and revolutions per mile change from 707 to 718.

285/45R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 245/65R16.

Size pages

Other comparisons with 245/65R16

Other comparisons with 285/45R18

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