305/35R19 vs 245/45R19

245/45R19 is 0.28 in (7.0 mm) taller than 305/35R19, a +1.01% diameter difference. With the speedometer set for 305/35R19, an indicated 60 mph is 60.6 mph on 245/45R19.

Is this a safe swap?

Diameter difference +1.01%: within the ±3% guideline

By overall diameter alone, 245/45R19 falls inside the ±3% range commonly used as a guideline when replacing 305/35R19. 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.

305/35R19 vs 245/45R19 differences
Measurement	305/35R19	245/45R19	Difference	% diff
Overall diameter	27.41 in (696.1 mm)	27.68 in (703.1 mm)	+0.28 in (+7.0 mm)	+1.01%
Sidewall height	4.20 in (106.8 mm)	4.34 in (110.3 mm)	+0.14 in (+3.5 mm)	+3.28%
Section width	12.01 in (305.0 mm)	9.65 in (245.0 mm)	−2.36 in (−60.0 mm)	−19.67%
Circumference	86.10 in (2,186.9 mm)	86.96 in (2,208.9 mm)	+0.87 in (+22.0 mm)	+1.01%
Revolutions per mile	736	729	−7	−1.00%

True speed with the speedometer calibrated for 305/35R19
Indicated	Actual on 305/35R19	Actual on 245/45R19	Difference
30 mph	30.0 mph	30.3 mph	+0.3 mph
60 mph	60.0 mph	60.6 mph	+0.6 mph
75 mph	75.0 mph	75.8 mph	+0.8 mph

Ride-height change: 245/45R19 raises the vehicle by 0.14 in (3.5 mm) at the axle (half the +7.0 mm diameter difference).

245/45R19 is 0.28 in taller than 305/35R19 and 60 mm narrower, a 1.01% difference in overall diameter.

With the speedometer calibrated for 305/35R19, an indicated 60 mph is actually 60.6 mph on 245/45R19, and revolutions per mile change from 736 to 729.

Both sizes mount on 19-inch wheels.

Size pages

Other comparisons with 305/35R19

Other comparisons with 245/45R19

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