TireSizesFinder

235/40R18 vs 265/30R19

265/30R19 is 0.14 in (3.6 mm) shorter than 235/40R18, a −0.56% diameter difference. With the speedometer set for 235/40R18, an indicated 60 mph is 59.7 mph on 265/30R19.

Is this a safe swap?

Diameter difference −0.56%: under 1%

By overall diameter alone, 265/30R19 is a near match for 235/40R18; 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: 235/40R18 (25.40 in) vs 265/30R19 (25.26 in)235/40R1825.40 in × 9.25 in265/30R1925.26 in × 10.43 in
Side profile and tread width, drawn to the same scale.
235/40R18 vs 265/30R19 differences
Measurement235/40R18265/30R19Difference% diff
Overall diameter25.40 in (645.2 mm)25.26 in (641.6 mm)−0.14 in (−3.6 mm)−0.56%
Sidewall height3.70 in (94.0 mm)3.13 in (79.5 mm)−0.57 in (−14.5 mm)−15.43%
Section width9.25 in (235.0 mm)10.43 in (265.0 mm)+1.18 in (+30.0 mm)+12.77%
Circumference79.80 in (2,027.0 mm)79.36 in (2,015.6 mm)−0.45 in (−11.3 mm)−0.56%
Revolutions per mile794798+4+0.56%
True speed with the speedometer calibrated for 235/40R18
IndicatedActual on 235/40R18Actual on 265/30R19Difference
30 mph30.0 mph29.8 mph−0.2 mph
60 mph60.0 mph59.7 mph−0.3 mph
75 mph75.0 mph74.6 mph−0.4 mph

Ride-height change: 265/30R19 lowers the vehicle by 0.07 in (1.8 mm) at the axle (half the −3.6 mm diameter difference).

265/30R19 is 0.14 in shorter than 235/40R18 and 30 mm wider, a 0.56% difference in overall diameter.

With the speedometer calibrated for 235/40R18, an indicated 60 mph is actually 59.7 mph on 265/30R19, and revolutions per mile change from 794 to 798.

265/30R19 mounts on a 19-inch wheel, a plus-1 fitment from the 18-inch wheel of 235/40R18.

Size pages

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