Tire Size Box

325/35R19 vs 315/40R19

315/40R19 compared with 325/35R19

+3.5% diameter, −0.4" width

315/40R19 is 28.92" tall vs 27.96". More than the 3% rule of thumb, so check carefully before switching.

28.0"19" rim4.5"12.8" wide
325/35R19 (solid) compared with 315/40R19 (dashed outline), drawn to scale

With 315/40R19 tires, when your speedometer says 60 mph you are really going

62.1 mph

315/40R19 is +0.96 inches (+3.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

325/35R19315/40R19Difference%
Overall diameter27.96"28.92"+0.96"+3.5%
Section width12.80"12.40"−0.39"−3.1%
Sidewall height4.48"4.96"+0.48"+10.8%
Circumference87.83"90.86"+3.03"+3.5%
Revolutions per mile721.4697.3−24.1−3.3%

Speedometer difference

If your vehicle came with 325/35R19 and you fit 315/40R19, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.0 mph+1.0 mph
40 mph41.4 mph+1.4 mph
50 mph51.7 mph+1.7 mph
60 mph62.1 mph+2.1 mph
65 mph67.2 mph+2.2 mph
70 mph72.4 mph+2.4 mph
75 mph77.6 mph+2.6 mph
80 mph82.8 mph+2.8 mph

Each size on its own

Questions

Which is bigger, 325/35R19 or 315/40R19?
315/40R19 is taller by 0.96 inches (28.92" vs 27.96"). 325/35R19 is wider by 0.39 inches.
Can I replace 325/35R19 with 315/40R19?
It is not recommended without checking carefully. The diameter difference is +3.5%, 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 315/40R19 change my speedometer?
When your speedometer reads 60 mph with 315/40R19 fitted (calibrated for 325/35R19), your real speed is 62.1 mph. Your odometer will under-count miles by about 3.5%.
Will 315/40R19 lift my vehicle?
Ride height changes by half the diameter difference: +0.48 inches of ground clearance at the axle.

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