Tire Size Box

315/25R24 vs 315/30R24

315/30R24 compared with 315/25R24

+4.1% diameter, 0.0" width

315/30R24 is 31.44" tall vs 30.20". More than the 3% rule of thumb, so check carefully before switching.

30.2"24" rim3.1"12.4" wide
315/25R24 (solid) compared with 315/30R24 (dashed outline), drawn to scale

With 315/30R24 tires, when your speedometer says 60 mph you are really going

62.5 mph

315/30R24 is +1.24 inches (+4.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

315/25R24315/30R24Difference%
Overall diameter30.20"31.44"+1.24"+4.1%
Section width12.40"12.40"0.00"0.0%
Sidewall height3.10"3.72"+0.62"+20.0%
Circumference94.88"98.77"+3.90"+4.1%
Revolutions per mile667.8641.5−26.3−3.9%

Speedometer difference

If your vehicle came with 315/25R24 and you fit 315/30R24, 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, 315/25R24 or 315/30R24?
315/30R24 is taller by 1.24 inches (31.44" vs 30.20"). 315/25R24 is the same width.
Can I replace 315/25R24 with 315/30R24?
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 315/30R24 change my speedometer?
When your speedometer reads 60 mph with 315/30R24 fitted (calibrated for 315/25R24), your real speed is 62.5 mph. Your odometer will under-count miles by about 4.1%.
Will 315/30R24 lift my vehicle?
Ride height changes by half the diameter difference: +0.62 inches of ground clearance at the axle.

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