Tire Size Box

275/30R24 vs 275/40R24

275/40R24 compared with 275/30R24

+7.1% diameter, 0.0" width

275/40R24 is 32.66" tall vs 30.50". More than the 3% rule of thumb, so check carefully before switching.

30.5"24" rim3.2"10.8" wide
275/30R24 (solid) compared with 275/40R24 (dashed outline), drawn to scale

With 275/40R24 tires, when your speedometer says 60 mph you are really going

64.3 mph

275/40R24 is +2.17 inches (+7.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

275/30R24275/40R24Difference%
Overall diameter30.50"32.66"+2.17"+7.1%
Section width10.83"10.83"0.00"0.0%
Sidewall height3.25"4.33"+1.08"+33.3%
Circumference95.81"102.61"+6.80"+7.1%
Revolutions per mile661.3617.5−43.8−6.6%

Speedometer difference

If your vehicle came with 275/30R24 and you fit 275/40R24, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.4 mph+1.4 mph
30 mph32.1 mph+2.1 mph
40 mph42.8 mph+2.8 mph
50 mph53.6 mph+3.6 mph
60 mph64.3 mph+4.3 mph
65 mph69.6 mph+4.6 mph
70 mph75.0 mph+5.0 mph
75 mph80.3 mph+5.3 mph
80 mph85.7 mph+5.7 mph

Each size on its own

Questions

Which is bigger, 275/30R24 or 275/40R24?
275/40R24 is taller by 2.17 inches (32.66" vs 30.50"). 275/30R24 is the same width.
Can I replace 275/30R24 with 275/40R24?
It is not recommended without checking carefully. The diameter difference is +7.1%, 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 275/40R24 change my speedometer?
When your speedometer reads 60 mph with 275/40R24 fitted (calibrated for 275/30R24), your real speed is 64.3 mph. Your odometer will under-count miles by about 7.1%.
Will 275/40R24 lift my vehicle?
Ride height changes by half the diameter difference: +1.08 inches of ground clearance at the axle.

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