Tire Size Box

325/25R19 vs 305/30R19

305/30R19 compared with 325/25R19

+3.2% diameter, −0.8" width

305/30R19 is 26.20" 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 305/30R19 (dashed outline), drawn to scale

With 305/30R19 tires, when your speedometer says 60 mph you are really going

61.9 mph

305/30R19 is +0.81 inches (+3.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

325/25R19305/30R19Difference%
Overall diameter25.40"26.20"+0.81"+3.2%
Section width12.80"12.01"−0.79"−6.2%
Sidewall height3.20"3.60"+0.40"+12.6%
Circumference79.79"82.32"+2.54"+3.2%
Revolutions per mile794.1769.6−24.5−3.1%

Speedometer difference

If your vehicle came with 325/25R19 and you fit 305/30R19, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.6 mph+0.6 mph
30 mph31.0 mph+1.0 mph
40 mph41.3 mph+1.3 mph
50 mph51.6 mph+1.6 mph
60 mph61.9 mph+1.9 mph
65 mph67.1 mph+2.1 mph
70 mph72.2 mph+2.2 mph
75 mph77.4 mph+2.4 mph
80 mph82.5 mph+2.5 mph

Each size on its own

Questions

Which is bigger, 325/25R19 or 305/30R19?
305/30R19 is taller by 0.81 inches (26.20" vs 25.40"). 325/25R19 is wider by 0.79 inches.
Can I replace 325/25R19 with 305/30R19?
It is not recommended without checking carefully. The diameter difference is +3.2%, 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 305/30R19 change my speedometer?
When your speedometer reads 60 mph with 305/30R19 fitted (calibrated for 325/25R19), your real speed is 61.9 mph. Your odometer will under-count miles by about 3.2%.
Will 305/30R19 lift my vehicle?
Ride height changes by half the diameter difference: +0.40 inches of ground clearance at the axle.

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