Tire Size Box

305/45R19 vs 305/55R19

305/55R19 compared with 305/45R19

+8.1% diameter, 0.0" width

305/55R19 is 32.21" tall vs 29.81". More than the 3% rule of thumb, so check carefully before switching.

29.8"19" rim5.4"12.0" wide
305/45R19 (solid) compared with 305/55R19 (dashed outline), drawn to scale

With 305/55R19 tires, when your speedometer says 60 mph you are really going

64.8 mph

305/55R19 is +2.40 inches (+8.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

305/45R19305/55R19Difference%
Overall diameter29.81"32.21"+2.40"+8.1%
Section width12.01"12.01"0.00"0.0%
Sidewall height5.40"6.60"+1.20"+22.2%
Circumference93.64"101.19"+7.54"+8.1%
Revolutions per mile676.6626.2−50.5−7.5%

Speedometer difference

If your vehicle came with 305/45R19 and you fit 305/55R19, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.6 mph+1.6 mph
30 mph32.4 mph+2.4 mph
40 mph43.2 mph+3.2 mph
50 mph54.0 mph+4.0 mph
60 mph64.8 mph+4.8 mph
65 mph70.2 mph+5.2 mph
70 mph75.6 mph+5.6 mph
75 mph81.0 mph+6.0 mph
80 mph86.4 mph+6.4 mph

Each size on its own

Questions

Which is bigger, 305/45R19 or 305/55R19?
305/55R19 is taller by 2.40 inches (32.21" vs 29.81"). 305/45R19 is the same width.
Can I replace 305/45R19 with 305/55R19?
It is not recommended without checking carefully. The diameter difference is +8.1%, 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 305/55R19 change my speedometer?
When your speedometer reads 60 mph with 305/55R19 fitted (calibrated for 305/45R19), your real speed is 64.8 mph. Your odometer will under-count miles by about 8.1%.
Will 305/55R19 lift my vehicle?
Ride height changes by half the diameter difference: +1.20 inches of ground clearance at the axle.

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