TireSizesFinder

275/40R18 vs 235/40R19

235/40R19 is 0.26 in (6.6 mm) shorter than 275/40R18, a −0.97% diameter difference. With the speedometer set for 275/40R18, an indicated 60 mph is 59.4 mph on 235/40R19.

Is this a safe swap?

Diameter difference −0.97%: under 1%

By overall diameter alone, 235/40R19 is a near match for 275/40R18; 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: 275/40R18 (26.66 in) vs 235/40R19 (26.40 in)275/40R1826.66 in × 10.83 in235/40R1926.40 in × 9.25 in
Side profile and tread width, drawn to the same scale.
275/40R18 vs 235/40R19 differences
Measurement275/40R18235/40R19Difference% diff
Overall diameter26.66 in (677.2 mm)26.40 in (670.6 mm)−0.26 in (−6.6 mm)−0.97%
Sidewall height4.33 in (110.0 mm)3.70 in (94.0 mm)−0.63 in (−16.0 mm)−14.55%
Section width10.83 in (275.0 mm)9.25 in (235.0 mm)−1.57 in (−40.0 mm)−14.55%
Circumference83.76 in (2,127.5 mm)82.94 in (2,106.8 mm)−0.82 in (−20.7 mm)−0.97%
Revolutions per mile756764+7+0.98%
True speed with the speedometer calibrated for 275/40R18
IndicatedActual on 275/40R18Actual on 235/40R19Difference
30 mph30.0 mph29.7 mph−0.3 mph
60 mph60.0 mph59.4 mph−0.6 mph
75 mph75.0 mph74.3 mph−0.7 mph

Ride-height change: 235/40R19 lowers the vehicle by 0.13 in (3.3 mm) at the axle (half the −6.6 mm diameter difference).

235/40R19 is 0.26 in shorter than 275/40R18 and 40 mm narrower, a 0.97% difference in overall diameter.

With the speedometer calibrated for 275/40R18, an indicated 60 mph is actually 59.4 mph on 235/40R19, and revolutions per mile change from 756 to 764.

235/40R19 mounts on a 19-inch wheel, a plus-1 fitment from the 18-inch wheel of 275/40R18.

Size pages

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