Tire Size Box

325/35R22 vs 315/40R22

315/40R22 compared with 325/35R22

+3.1% diameter, −0.4" width

315/40R22 is 31.92" tall vs 30.96". More than the 3% rule of thumb, so check carefully before switching.

31.0"22" rim4.5"12.8" wide
325/35R22 (solid) compared with 315/40R22 (dashed outline), drawn to scale

With 315/40R22 tires, when your speedometer says 60 mph you are really going

61.9 mph

315/40R22 is +0.96 inches (+3.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

325/35R22315/40R22Difference%
Overall diameter30.96"31.92"+0.96"+3.1%
Section width12.80"12.40"−0.39"−3.1%
Sidewall height4.48"4.96"+0.48"+10.8%
Circumference97.25"100.28"+3.03"+3.1%
Revolutions per mile651.5631.8−19.7−3.0%

Speedometer difference

If your vehicle came with 325/35R22 and you fit 315/40R22, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.6 mph+0.6 mph
30 mph30.9 mph+0.9 mph
40 mph41.2 mph+1.2 mph
50 mph51.6 mph+1.6 mph
60 mph61.9 mph+1.9 mph
65 mph67.0 mph+2.0 mph
70 mph72.2 mph+2.2 mph
75 mph77.3 mph+2.3 mph
80 mph82.5 mph+2.5 mph

Each size on its own

Questions

Which is bigger, 325/35R22 or 315/40R22?
315/40R22 is taller by 0.96 inches (31.92" vs 30.96"). 325/35R22 is wider by 0.39 inches.
Can I replace 325/35R22 with 315/40R22?
It is not recommended without checking carefully. The diameter difference is +3.1%, 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 315/40R22 change my speedometer?
When your speedometer reads 60 mph with 315/40R22 fitted (calibrated for 325/35R22), your real speed is 61.9 mph. Your odometer will under-count miles by about 3.1%.
Will 315/40R22 lift my vehicle?
Ride height changes by half the diameter difference: +0.48 inches of ground clearance at the axle.

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