Tire Size Box

355/25R19 vs 345/30R19

345/30R19 compared with 355/25R19

+4.5% diameter, −0.4" width

345/30R19 is 27.15" tall vs 25.99". More than the 3% rule of thumb, so check carefully before switching.

26.0"19" rim3.5"14.0" wide
355/25R19 (solid) compared with 345/30R19 (dashed outline), drawn to scale

With 345/30R19 tires, when your speedometer says 60 mph you are really going

62.7 mph

345/30R19 is +1.16 inches (+4.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

355/25R19345/30R19Difference%
Overall diameter25.99"27.15"+1.16"+4.5%
Section width13.98"13.58"−0.39"−2.8%
Sidewall height3.49"4.07"+0.58"+16.6%
Circumference81.64"85.29"+3.65"+4.5%
Revolutions per mile776.0742.9−33.2−4.3%

Speedometer difference

If your vehicle came with 355/25R19 and you fit 345/30R19, 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 mph62.7 mph+2.7 mph
65 mph67.9 mph+2.9 mph
70 mph73.1 mph+3.1 mph
75 mph78.4 mph+3.4 mph
80 mph83.6 mph+3.6 mph

Each size on its own

Questions

Which is bigger, 355/25R19 or 345/30R19?
345/30R19 is taller by 1.16 inches (27.15" vs 25.99"). 355/25R19 is wider by 0.39 inches.
Can I replace 355/25R19 with 345/30R19?
It is not recommended without checking carefully. The diameter difference is +4.5%, 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 345/30R19 change my speedometer?
When your speedometer reads 60 mph with 345/30R19 fitted (calibrated for 355/25R19), your real speed is 62.7 mph. Your odometer will under-count miles by about 4.5%.
Will 345/30R19 lift my vehicle?
Ride height changes by half the diameter difference: +0.58 inches of ground clearance at the axle.

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