Tire Size Box

315/25R22 vs 315/30R22

315/30R22 compared with 315/25R22

+4.4% diameter, 0.0" width

315/30R22 is 29.44" tall vs 28.20". More than the 3% rule of thumb, so check carefully before switching.

28.2"22" rim3.1"12.4" wide
315/25R22 (solid) compared with 315/30R22 (dashed outline), drawn to scale

With 315/30R22 tires, when your speedometer says 60 mph you are really going

62.6 mph

315/30R22 is +1.24 inches (+4.4%) in overall diameter. That is more than the 3% most shops and makers recommend.

315/25R22315/30R22Difference%
Overall diameter28.20"29.44"+1.24"+4.4%
Section width12.40"12.40"0.00"0.0%
Sidewall height3.10"3.72"+0.62"+20.0%
Circumference88.60"92.49"+3.90"+4.4%
Revolutions per mile715.2685.0−30.1−4.2%

Speedometer difference

If your vehicle came with 315/25R22 and you fit 315/30R22, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.9 mph+0.9 mph
30 mph31.3 mph+1.3 mph
40 mph41.8 mph+1.8 mph
50 mph52.2 mph+2.2 mph
60 mph62.6 mph+2.6 mph
65 mph67.9 mph+2.9 mph
70 mph73.1 mph+3.1 mph
75 mph78.3 mph+3.3 mph
80 mph83.5 mph+3.5 mph

Each size on its own

Questions

Which is bigger, 315/25R22 or 315/30R22?
315/30R22 is taller by 1.24 inches (29.44" vs 28.20"). 315/25R22 is the same width.
Can I replace 315/25R22 with 315/30R22?
It is not recommended without checking carefully. The diameter difference is +4.4%, 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 315/30R22 change my speedometer?
When your speedometer reads 60 mph with 315/30R22 fitted (calibrated for 315/25R22), your real speed is 62.6 mph. Your odometer will under-count miles by about 4.4%.
Will 315/30R22 lift my vehicle?
Ride height changes by half the diameter difference: +0.62 inches of ground clearance at the axle.

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