Tire Size Box

355/40R19 vs 345/45R19

345/45R19 compared with 355/40R19

+3.5% diameter, −0.4" width

345/45R19 is 31.22" tall vs 30.18". More than the 3% rule of thumb, so check carefully before switching.

30.2"19" rim5.6"14.0" wide
355/40R19 (solid) compared with 345/45R19 (dashed outline), drawn to scale

With 345/45R19 tires, when your speedometer says 60 mph you are really going

62.1 mph

345/45R19 is +1.04 inches (+3.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

355/40R19345/45R19Difference%
Overall diameter30.18"31.22"+1.04"+3.5%
Section width13.98"13.58"−0.39"−2.8%
Sidewall height5.59"6.11"+0.52"+9.3%
Circumference94.82"98.09"+3.28"+3.5%
Revolutions per mile668.2645.9−22.3−3.3%

Speedometer difference

If your vehicle came with 355/40R19 and you fit 345/45R19, 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 mph82.8 mph+2.8 mph

Each size on its own

Questions

Which is bigger, 355/40R19 or 345/45R19?
345/45R19 is taller by 1.04 inches (31.22" vs 30.18"). 355/40R19 is wider by 0.39 inches.
Can I replace 355/40R19 with 345/45R19?
It is not recommended without checking carefully. The diameter difference is +3.5%, 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 345/45R19 change my speedometer?
When your speedometer reads 60 mph with 345/45R19 fitted (calibrated for 355/40R19), your real speed is 62.1 mph. Your odometer will under-count miles by about 3.5%.
Will 345/45R19 lift my vehicle?
Ride height changes by half the diameter difference: +0.52 inches of ground clearance at the axle.

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