Tire Size Box

245/30R22 vs 245/40R22

245/40R22 compared with 245/30R22

+6.9% diameter, 0.0" width

245/40R22 is 29.72" tall vs 27.79". More than the 3% rule of thumb, so check carefully before switching.

27.8"22" rim2.9"9.6" wide
245/30R22 (solid) compared with 245/40R22 (dashed outline), drawn to scale

With 245/40R22 tires, when your speedometer says 60 mph you are really going

64.2 mph

245/40R22 is +1.93 inches (+6.9%) in overall diameter. That is more than the 3% most shops and makers recommend.

245/30R22245/40R22Difference%
Overall diameter27.79"29.72"+1.93"+6.9%
Section width9.65"9.65"0.00"0.0%
Sidewall height2.89"3.86"+0.96"+33.3%
Circumference87.30"93.36"+6.06"+6.9%
Revolutions per mile725.8678.7−47.1−6.5%

Speedometer difference

If your vehicle came with 245/30R22 and you fit 245/40R22, 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 mph53.5 mph+3.5 mph
60 mph64.2 mph+4.2 mph
65 mph69.5 mph+4.5 mph
70 mph74.9 mph+4.9 mph
75 mph80.2 mph+5.2 mph
80 mph85.6 mph+5.6 mph

Each size on its own

Questions

Which is bigger, 245/30R22 or 245/40R22?
245/40R22 is taller by 1.93 inches (29.72" vs 27.79"). 245/30R22 is the same width.
Can I replace 245/30R22 with 245/40R22?
It is not recommended without checking carefully. The diameter difference is +6.9%, 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 245/40R22 change my speedometer?
When your speedometer reads 60 mph with 245/40R22 fitted (calibrated for 245/30R22), your real speed is 64.2 mph. Your odometer will under-count miles by about 6.9%.
Will 245/40R22 lift my vehicle?
Ride height changes by half the diameter difference: +0.96 inches of ground clearance at the axle.

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