Tire Size Box

345/45R19 vs 345/55R19

345/55R19 compared with 345/45R19

+8.7% diameter, 0.0" width

345/55R19 is 33.94" tall vs 31.22". More than the 3% rule of thumb, so check carefully before switching.

31.2"19" rim6.1"13.6" wide
345/45R19 (solid) compared with 345/55R19 (dashed outline), drawn to scale

With 345/55R19 tires, when your speedometer says 60 mph you are really going

65.2 mph

345/55R19 is +2.72 inches (+8.7%) in overall diameter. That is more than the 3% most shops and makers recommend.

345/45R19345/55R19Difference%
Overall diameter31.22"33.94"+2.72"+8.7%
Section width13.58"13.58"0.00"0.0%
Sidewall height6.11"7.47"+1.36"+22.2%
Circumference98.09"106.63"+8.53"+8.7%
Revolutions per mile645.9594.2−51.7−8.0%

Speedometer difference

If your vehicle came with 345/45R19 and you fit 345/55R19, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.7 mph+1.7 mph
30 mph32.6 mph+2.6 mph
40 mph43.5 mph+3.5 mph
50 mph54.4 mph+4.4 mph
60 mph65.2 mph+5.2 mph
65 mph70.7 mph+5.7 mph
70 mph76.1 mph+6.1 mph
75 mph81.5 mph+6.5 mph
80 mph87.0 mph+7.0 mph

Each size on its own

Questions

Which is bigger, 345/45R19 or 345/55R19?
345/55R19 is taller by 2.72 inches (33.94" vs 31.22"). 345/45R19 is the same width.
Can I replace 345/45R19 with 345/55R19?
It is not recommended without checking carefully. The diameter difference is +8.7%, 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 345/55R19 change my speedometer?
When your speedometer reads 60 mph with 345/55R19 fitted (calibrated for 345/45R19), your real speed is 65.2 mph. Your odometer will under-count miles by about 8.7%.
Will 345/55R19 lift my vehicle?
Ride height changes by half the diameter difference: +1.36 inches of ground clearance at the axle.

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