Tire Size Box

325/25R19 vs 315/30R19

315/30R19 compared with 325/25R19

+4.1% diameter, −0.4" width

315/30R19 is 26.44" tall vs 25.40". More than the 3% rule of thumb, so check carefully before switching.

25.4"19" rim3.2"12.8" wide
325/25R19 (solid) compared with 315/30R19 (dashed outline), drawn to scale

With 315/30R19 tires, when your speedometer says 60 mph you are really going

62.5 mph

315/30R19 is +1.04 inches (+4.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

325/25R19315/30R19Difference%
Overall diameter25.40"26.44"+1.04"+4.1%
Section width12.80"12.40"−0.39"−3.1%
Sidewall height3.20"3.72"+0.52"+16.3%
Circumference79.79"83.07"+3.28"+4.1%
Revolutions per mile794.1762.8−31.3−3.9%

Speedometer difference

If your vehicle came with 325/25R19 and you fit 315/30R19, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.8 mph+0.8 mph
30 mph31.2 mph+1.2 mph
40 mph41.6 mph+1.6 mph
50 mph52.1 mph+2.1 mph
60 mph62.5 mph+2.5 mph
65 mph67.7 mph+2.7 mph
70 mph72.9 mph+2.9 mph
75 mph78.1 mph+3.1 mph
80 mph83.3 mph+3.3 mph

Each size on its own

Questions

Which is bigger, 325/25R19 or 315/30R19?
315/30R19 is taller by 1.04 inches (26.44" vs 25.40"). 325/25R19 is wider by 0.39 inches.
Can I replace 325/25R19 with 315/30R19?
It is not recommended without checking carefully. The diameter difference is +4.1%, 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 315/30R19 change my speedometer?
When your speedometer reads 60 mph with 315/30R19 fitted (calibrated for 325/25R19), your real speed is 62.5 mph. Your odometer will under-count miles by about 4.1%.
Will 315/30R19 lift my vehicle?
Ride height changes by half the diameter difference: +0.52 inches of ground clearance at the axle.

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