Tire Size Box

275/30R19 vs 275/40R19

275/40R19 compared with 275/30R19

+8.5% diameter, 0.0" width

275/40R19 is 27.66" tall vs 25.50". More than the 3% rule of thumb, so check carefully before switching.

25.5"19" rim3.2"10.8" wide
275/30R19 (solid) compared with 275/40R19 (dashed outline), drawn to scale

With 275/40R19 tires, when your speedometer says 60 mph you are really going

65.1 mph

275/40R19 is +2.17 inches (+8.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

275/30R19275/40R19Difference%
Overall diameter25.50"27.66"+2.17"+8.5%
Section width10.83"10.83"0.00"0.0%
Sidewall height3.25"4.33"+1.08"+33.3%
Circumference80.10"86.90"+6.80"+8.5%
Revolutions per mile791.0729.1−61.9−7.8%

Speedometer difference

If your vehicle came with 275/30R19 and you fit 275/40R19, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.7 mph+1.7 mph
30 mph32.5 mph+2.5 mph
40 mph43.4 mph+3.4 mph
50 mph54.2 mph+4.2 mph
60 mph65.1 mph+5.1 mph
65 mph70.5 mph+5.5 mph
70 mph75.9 mph+5.9 mph
75 mph81.4 mph+6.4 mph
80 mph86.8 mph+6.8 mph

Each size on its own

Questions

Which is bigger, 275/30R19 or 275/40R19?
275/40R19 is taller by 2.17 inches (27.66" vs 25.50"). 275/30R19 is the same width.
Can I replace 275/30R19 with 275/40R19?
It is not recommended without checking carefully. The diameter difference is +8.5%, 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 275/40R19 change my speedometer?
When your speedometer reads 60 mph with 275/40R19 fitted (calibrated for 275/30R19), your real speed is 65.1 mph. Your odometer will under-count miles by about 8.5%.
Will 275/40R19 lift my vehicle?
Ride height changes by half the diameter difference: +1.08 inches of ground clearance at the axle.

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