305/35R19 vs 275/40R19

275/40R19 is 0.26 in (6.5 mm) taller than 305/35R19, a +0.93% diameter difference. With the speedometer set for 305/35R19, an indicated 60 mph is 60.6 mph on 275/40R19.

Is this a safe swap?

Diameter difference +0.93%: under 1%

By overall diameter alone, 275/40R19 is a near match for 305/35R19; 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.

305/35R19 vs 275/40R19 differences
Measurement	305/35R19	275/40R19	Difference	% diff
Overall diameter	27.41 in (696.1 mm)	27.66 in (702.6 mm)	+0.26 in (+6.5 mm)	+0.93%
Sidewall height	4.20 in (106.8 mm)	4.33 in (110.0 mm)	+0.13 in (+3.3 mm)	+3.04%
Section width	12.01 in (305.0 mm)	10.83 in (275.0 mm)	−1.18 in (−30.0 mm)	−9.84%
Circumference	86.10 in (2,186.9 mm)	86.90 in (2,207.3 mm)	+0.80 in (+20.4 mm)	+0.93%
Revolutions per mile	736	729	−7	−0.93%

True speed with the speedometer calibrated for 305/35R19
Indicated	Actual on 305/35R19	Actual on 275/40R19	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	75.7 mph	+0.7 mph

Ride-height change: 275/40R19 raises the vehicle by 0.13 in (3.3 mm) at the axle (half the +6.5 mm diameter difference).

275/40R19 is 0.26 in taller than 305/35R19 and 30 mm narrower, a 0.93% difference in overall diameter.

With the speedometer calibrated for 305/35R19, an indicated 60 mph is actually 60.6 mph on 275/40R19, 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 275/40R19

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