225/70R16 vs 285/45R18

285/45R18 is 0.30 in (7.7 mm) shorter than 225/70R16, a −1.07% diameter difference. With the speedometer set for 225/70R16, an indicated 60 mph is 59.4 mph on 285/45R18.

Is this a safe swap?

Diameter difference −1.07%: within the ±3% guideline

By overall diameter alone, 285/45R18 falls inside the ±3% range commonly used as a guideline when replacing 225/70R16. 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.

225/70R16 vs 285/45R18 differences
Measurement	225/70R16	285/45R18	Difference	% diff
Overall diameter	28.40 in (721.4 mm)	28.10 in (713.7 mm)	−0.30 in (−7.7 mm)	−1.07%
Sidewall height	6.20 in (157.5 mm)	5.05 in (128.3 mm)	−1.15 in (−29.2 mm)	−18.57%
Section width	8.86 in (225.0 mm)	11.22 in (285.0 mm)	+2.36 in (+60.0 mm)	+26.67%
Circumference	89.23 in (2,266.3 mm)	88.27 in (2,242.2 mm)	−0.95 in (−24.2 mm)	−1.07%
Revolutions per mile	710	718	+8	+1.08%

True speed with the speedometer calibrated for 225/70R16
Indicated	Actual on 225/70R16	Actual on 285/45R18	Difference
30 mph	30.0 mph	29.7 mph	−0.3 mph
60 mph	60.0 mph	59.4 mph	−0.6 mph
75 mph	75.0 mph	74.2 mph	−0.8 mph

Ride-height change: 285/45R18 lowers the vehicle by 0.15 in (3.8 mm) at the axle (half the −7.7 mm diameter difference).

285/45R18 is 0.30 in shorter than 225/70R16 and 60 mm wider, a 1.07% difference in overall diameter.

With the speedometer calibrated for 225/70R16, an indicated 60 mph is actually 59.4 mph on 285/45R18, and revolutions per mile change from 710 to 718.

285/45R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 225/70R16.

Size pages

Other comparisons with 225/70R16

Other comparisons with 285/45R18

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