Tire Size Box

345/25R19 vs 325/30R19

325/30R19 compared with 345/25R19

+3.4% diameter, −0.8" width

325/30R19 is 26.68" tall vs 25.79". More than the 3% rule of thumb, so check carefully before switching.

25.8"19" rim3.4"13.6" wide
345/25R19 (solid) compared with 325/30R19 (dashed outline), drawn to scale

With 325/30R19 tires, when your speedometer says 60 mph you are really going

62.1 mph

325/30R19 is +0.89 inches (+3.4%) in overall diameter. That is more than the 3% most shops and makers recommend.

345/25R19325/30R19Difference%
Overall diameter25.79"26.68"+0.89"+3.4%
Section width13.58"12.80"−0.79"−5.8%
Sidewall height3.40"3.84"+0.44"+13.0%
Circumference81.03"83.81"+2.78"+3.4%
Revolutions per mile782.0756.0−26.0−3.3%

Speedometer difference

If your vehicle came with 345/25R19 and you fit 325/30R19, 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 mph82.7 mph+2.7 mph

Each size on its own

Questions

Which is bigger, 345/25R19 or 325/30R19?
325/30R19 is taller by 0.89 inches (26.68" vs 25.79"). 345/25R19 is wider by 0.79 inches.
Can I replace 345/25R19 with 325/30R19?
It is not recommended without checking carefully. The diameter difference is +3.4%, 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 325/30R19 change my speedometer?
When your speedometer reads 60 mph with 325/30R19 fitted (calibrated for 345/25R19), your real speed is 62.1 mph. Your odometer will under-count miles by about 3.4%.
Will 325/30R19 lift my vehicle?
Ride height changes by half the diameter difference: +0.44 inches of ground clearance at the axle.

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