TireSizesFinder

255/40R17 vs 245/30R19

245/30R19 is 0.24 in (6.2 mm) shorter than 255/40R17, a −0.98% diameter difference. With the speedometer set for 255/40R17, an indicated 60 mph is 59.4 mph on 245/30R19.

Is this a safe swap?

Diameter difference −0.98%: under 1%

By overall diameter alone, 245/30R19 is a near match for 255/40R17; 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: 255/40R17 (25.03 in) vs 245/30R19 (24.79 in)255/40R1725.03 in × 10.04 in245/30R1924.79 in × 9.65 in
Side profile and tread width, drawn to the same scale.
255/40R17 vs 245/30R19 differences
Measurement255/40R17245/30R19Difference% diff
Overall diameter25.03 in (635.8 mm)24.79 in (629.6 mm)−0.24 in (−6.2 mm)−0.98%
Sidewall height4.02 in (102.0 mm)2.89 in (73.5 mm)−1.12 in (−28.5 mm)−27.94%
Section width10.04 in (255.0 mm)9.65 in (245.0 mm)−0.39 in (−10.0 mm)−3.92%
Circumference78.64 in (1,997.4 mm)77.87 in (1,977.9 mm)−0.77 in (−19.5 mm)−0.98%
Revolutions per mile806814+8+0.98%
True speed with the speedometer calibrated for 255/40R17
IndicatedActual on 255/40R17Actual on 245/30R19Difference
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: 245/30R19 lowers the vehicle by 0.12 in (3.1 mm) at the axle (half the −6.2 mm diameter difference).

245/30R19 is 0.24 in shorter than 255/40R17 and 10 mm narrower, a 0.98% difference in overall diameter.

With the speedometer calibrated for 255/40R17, an indicated 60 mph is actually 59.4 mph on 245/30R19, and revolutions per mile change from 806 to 814.

245/30R19 mounts on a 19-inch wheel, a plus-2 fitment from the 17-inch wheel of 255/40R17.

Size pages

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