195/55R16 vs 245/35R18

245/35R18 is 0.31 in (7.8 mm) taller than 195/55R16, a +1.26% diameter difference. With the speedometer set for 195/55R16, an indicated 60 mph is 60.8 mph on 245/35R18.

Is this a safe swap?

Diameter difference +1.26%: within the ±3% guideline

By overall diameter alone, 245/35R18 falls inside the ±3% range commonly used as a guideline when replacing 195/55R16. 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.

195/55R16 vs 245/35R18 differences
Measurement	195/55R16	245/35R18	Difference	% diff
Overall diameter	24.44 in (620.9 mm)	24.75 in (628.7 mm)	+0.31 in (+7.8 mm)	+1.26%
Sidewall height	4.22 in (107.3 mm)	3.38 in (85.8 mm)	−0.85 in (−21.5 mm)	−20.05%
Section width	7.68 in (195.0 mm)	9.65 in (245.0 mm)	+1.97 in (+50.0 mm)	+25.64%
Circumference	76.80 in (1,950.6 mm)	77.76 in (1,975.1 mm)	+0.96 in (+24.5 mm)	+1.26%
Revolutions per mile	825	815	−10	−1.24%

True speed with the speedometer calibrated for 195/55R16
Indicated	Actual on 195/55R16	Actual on 245/35R18	Difference
30 mph	30.0 mph	30.4 mph	+0.4 mph
60 mph	60.0 mph	60.8 mph	+0.8 mph
75 mph	75.0 mph	75.9 mph	+0.9 mph

Ride-height change: 245/35R18 raises the vehicle by 0.15 in (3.9 mm) at the axle (half the +7.8 mm diameter difference).

245/35R18 is 0.31 in taller than 195/55R16 and 50 mm wider, a 1.26% difference in overall diameter.

With the speedometer calibrated for 195/55R16, an indicated 60 mph is actually 60.8 mph on 245/35R18, and revolutions per mile change from 825 to 815.

245/35R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 195/55R16.

Size pages

Other comparisons with 195/55R16

Other comparisons with 245/35R18

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