Tire Size Box

325/25R24 vs 325/30R24

325/30R24 compared with 325/25R24

+4.2% diameter, 0.0" width

325/30R24 is 31.68" tall vs 30.40". More than the 3% rule of thumb, so check carefully before switching.

30.4"24" rim3.2"12.8" wide
325/25R24 (solid) compared with 325/30R24 (dashed outline), drawn to scale

With 325/30R24 tires, when your speedometer says 60 mph you are really going

62.5 mph

325/30R24 is +1.28 inches (+4.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

325/25R24325/30R24Difference%
Overall diameter30.40"31.68"+1.28"+4.2%
Section width12.80"12.80"0.00"0.0%
Sidewall height3.20"3.84"+0.64"+20.0%
Circumference95.50"99.52"+4.02"+4.2%
Revolutions per mile663.5636.7−26.8−4.0%

Speedometer difference

If your vehicle came with 325/25R24 and you fit 325/30R24, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.8 mph+0.8 mph
30 mph31.3 mph+1.3 mph
40 mph41.7 mph+1.7 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 mph78.2 mph+3.2 mph
80 mph83.4 mph+3.4 mph

Each size on its own

Questions

Which is bigger, 325/25R24 or 325/30R24?
325/30R24 is taller by 1.28 inches (31.68" vs 30.40"). 325/25R24 is the same width.
Can I replace 325/25R24 with 325/30R24?
It is not recommended without checking carefully. The diameter difference is +4.2%, 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 325/30R24 change my speedometer?
When your speedometer reads 60 mph with 325/30R24 fitted (calibrated for 325/25R24), your real speed is 62.5 mph. Your odometer will under-count miles by about 4.2%.
Will 325/30R24 lift my vehicle?
Ride height changes by half the diameter difference: +0.64 inches of ground clearance at the axle.

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