Tire Size Box

325/45R19 vs 325/55R19

325/55R19 compared with 325/45R19

+8.4% diameter, 0.0" width

325/55R19 is 33.07" tall vs 30.52". More than the 3% rule of thumb, so check carefully before switching.

30.5"19" rim5.8"12.8" wide
325/45R19 (solid) compared with 325/55R19 (dashed outline), drawn to scale

With 325/55R19 tires, when your speedometer says 60 mph you are really going

65.0 mph

325/55R19 is +2.56 inches (+8.4%) in overall diameter. That is more than the 3% most shops and makers recommend.

325/45R19325/55R19Difference%
Overall diameter30.52"33.07"+2.56"+8.4%
Section width12.80"12.80"0.00"0.0%
Sidewall height5.76"7.04"+1.28"+22.2%
Circumference95.87"103.91"+8.04"+8.4%
Revolutions per mile660.9609.8−51.1−7.7%

Speedometer difference

If your vehicle came with 325/45R19 and you fit 325/55R19, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.7 mph+1.7 mph
30 mph32.5 mph+2.5 mph
40 mph43.4 mph+3.4 mph
50 mph54.2 mph+4.2 mph
60 mph65.0 mph+5.0 mph
65 mph70.5 mph+5.5 mph
70 mph75.9 mph+5.9 mph
75 mph81.3 mph+6.3 mph
80 mph86.7 mph+6.7 mph

Each size on its own

Questions

Which is bigger, 325/45R19 or 325/55R19?
325/55R19 is taller by 2.56 inches (33.07" vs 30.52"). 325/45R19 is the same width.
Can I replace 325/45R19 with 325/55R19?
It is not recommended without checking carefully. The diameter difference is +8.4%, 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 325/55R19 change my speedometer?
When your speedometer reads 60 mph with 325/55R19 fitted (calibrated for 325/45R19), your real speed is 65.0 mph. Your odometer will under-count miles by about 8.4%.
Will 325/55R19 lift my vehicle?
Ride height changes by half the diameter difference: +1.28 inches of ground clearance at the axle.

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