TireSizesFinder

275/45R18 vs 275/40R19

275/40R19 is 0.08 in (2.1 mm) shorter than 275/45R18, a −0.30% diameter difference. With the speedometer set for 275/45R18, an indicated 60 mph is 59.8 mph on 275/40R19.

Is this a safe swap?

Diameter difference −0.30%: under 1%

By overall diameter alone, 275/40R19 is a near match for 275/45R18; the speedometer changes by less than 1%. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 275/45R18 (27.74 in) vs 275/40R19 (27.66 in)275/45R1827.74 in × 10.83 in275/40R1927.66 in × 10.83 in
Side profile and tread width, drawn to the same scale.
275/45R18 vs 275/40R19 differences
Measurement275/45R18275/40R19Difference% diff
Overall diameter27.74 in (704.7 mm)27.66 in (702.6 mm)−0.08 in (−2.1 mm)−0.30%
Sidewall height4.87 in (123.8 mm)4.33 in (110.0 mm)−0.54 in (−13.7 mm)−11.11%
Section width10.83 in (275.0 mm)10.83 in (275.0 mm)0.00 in (0.0 mm)0.00%
Circumference87.16 in (2,213.9 mm)86.90 in (2,207.3 mm)−0.26 in (−6.6 mm)−0.30%
Revolutions per mile727729+2+0.30%
True speed with the speedometer calibrated for 275/45R18
IndicatedActual on 275/45R18Actual on 275/40R19Difference
30 mph30.0 mph29.9 mph−0.1 mph
60 mph60.0 mph59.8 mph−0.2 mph
75 mph75.0 mph74.8 mph−0.2 mph

Ride-height change: 275/40R19 lowers the vehicle by 0.04 in (1.1 mm) at the axle (half the −2.1 mm diameter difference).

275/40R19 is 0.08 in shorter than 275/45R18 and the same width, a 0.30% difference in overall diameter.

With the speedometer calibrated for 275/45R18, an indicated 60 mph is actually 59.8 mph on 275/40R19, and revolutions per mile change from 727 to 729.

275/40R19 mounts on a 19-inch wheel, a plus-1 fitment from the 18-inch wheel of 275/45R18.

Size pages

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Source: Calculated from standard tire geometry formulas. Verified . How these numbers are calculated.