245/50R18 vs 305/35R19

305/35R19 is 0.24 in (6.1 mm) shorter than 245/50R18, a −0.87% diameter difference. With the speedometer set for 245/50R18, an indicated 60 mph is 59.5 mph on 305/35R19.

Is this a safe swap?

Diameter difference −0.87%: under 1%

By overall diameter alone, 305/35R19 is a near match for 245/50R18; the speedometer changes by less than 1%. 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.

245/50R18 vs 305/35R19 differences
Measurement	245/50R18	305/35R19	Difference	% diff
Overall diameter	27.65 in (702.2 mm)	27.41 in (696.1 mm)	−0.24 in (−6.1 mm)	−0.87%
Sidewall height	4.82 in (122.5 mm)	4.20 in (106.8 mm)	−0.62 in (−15.7 mm)	−12.86%
Section width	9.65 in (245.0 mm)	12.01 in (305.0 mm)	+2.36 in (+60.0 mm)	+24.49%
Circumference	86.85 in (2,206.0 mm)	86.10 in (2,186.9 mm)	−0.75 in (−19.2 mm)	−0.87%
Revolutions per mile	730	736	+6	+0.88%

True speed with the speedometer calibrated for 245/50R18
Indicated	Actual on 245/50R18	Actual on 305/35R19	Difference
30 mph	30.0 mph	29.7 mph	−0.3 mph
60 mph	60.0 mph	59.5 mph	−0.5 mph
75 mph	75.0 mph	74.3 mph	−0.7 mph

Ride-height change: 305/35R19 lowers the vehicle by 0.12 in (3.1 mm) at the axle (half the −6.1 mm diameter difference).

305/35R19 is 0.24 in shorter than 245/50R18 and 60 mm wider, a 0.87% difference in overall diameter.

With the speedometer calibrated for 245/50R18, an indicated 60 mph is actually 59.5 mph on 305/35R19, and revolutions per mile change from 730 to 736.

305/35R19 mounts on a 19-inch wheel, a plus-1 fitment from the 18-inch wheel of 245/50R18.

Size pages

Other comparisons with 245/50R18

Other comparisons with 305/35R19

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