Tire Size Box

285/30R19 vs 285/40R19

285/40R19 compared with 285/30R19

+8.7% diameter, 0.0" width

285/40R19 is 27.98" tall vs 25.73". More than the 3% rule of thumb, so check carefully before switching.

25.7"19" rim3.4"11.2" wide
285/30R19 (solid) compared with 285/40R19 (dashed outline), drawn to scale

With 285/40R19 tires, when your speedometer says 60 mph you are really going

65.2 mph

285/40R19 is +2.24 inches (+8.7%) in overall diameter. That is more than the 3% most shops and makers recommend.

285/30R19285/40R19Difference%
Overall diameter25.73"27.98"+2.24"+8.7%
Section width11.22"11.22"0.00"0.0%
Sidewall height3.37"4.49"+1.12"+33.3%
Circumference80.84"87.89"+7.05"+8.7%
Revolutions per mile783.8720.9−62.9−8.0%

Speedometer difference

If your vehicle came with 285/30R19 and you fit 285/40R19, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.7 mph+1.7 mph
30 mph32.6 mph+2.6 mph
40 mph43.5 mph+3.5 mph
50 mph54.4 mph+4.4 mph
60 mph65.2 mph+5.2 mph
65 mph70.7 mph+5.7 mph
70 mph76.1 mph+6.1 mph
75 mph81.5 mph+6.5 mph
80 mph87.0 mph+7.0 mph

Each size on its own

Questions

Which is bigger, 285/30R19 or 285/40R19?
285/40R19 is taller by 2.24 inches (27.98" vs 25.73"). 285/30R19 is the same width.
Can I replace 285/30R19 with 285/40R19?
It is not recommended without checking carefully. The diameter difference is +8.7%, more than the 3% most shops and makers allow. It will throw off the speedometer and may affect ABS, stability control and clearance.
How much will 285/40R19 change my speedometer?
When your speedometer reads 60 mph with 285/40R19 fitted (calibrated for 285/30R19), your real speed is 65.2 mph. Your odometer will under-count miles by about 8.7%.
Will 285/40R19 lift my vehicle?
Ride height changes by half the diameter difference: +1.12 inches of ground clearance at the axle.

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