Tire Size Box

355/40R19 vs 355/45R19

355/45R19 compared with 355/40R19

+4.6% diameter, 0.0" width

355/45R19 is 31.58" 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 355/45R19 (dashed outline), drawn to scale

With 355/45R19 tires, when your speedometer says 60 mph you are really going

62.8 mph

355/45R19 is +1.40 inches (+4.6%) in overall diameter. That is more than the 3% most shops and makers recommend.

355/40R19355/45R19Difference%
Overall diameter30.18"31.58"+1.40"+4.6%
Section width13.98"13.98"0.00"0.0%
Sidewall height5.59"6.29"+0.70"+12.5%
Circumference94.82"99.21"+4.39"+4.6%
Revolutions per mile668.2638.7−29.6−4.4%

Speedometer difference

If your vehicle came with 355/40R19 and you fit 355/45R19, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.9 mph+0.9 mph
30 mph31.4 mph+1.4 mph
40 mph41.9 mph+1.9 mph
50 mph52.3 mph+2.3 mph
60 mph62.8 mph+2.8 mph
65 mph68.0 mph+3.0 mph
70 mph73.2 mph+3.2 mph
75 mph78.5 mph+3.5 mph
80 mph83.7 mph+3.7 mph

Each size on its own

Questions

Which is bigger, 355/40R19 or 355/45R19?
355/45R19 is taller by 1.40 inches (31.58" vs 30.18"). 355/40R19 is the same width.
Can I replace 355/40R19 with 355/45R19?
It is not recommended without checking carefully. The diameter difference is +4.6%, 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 355/45R19 change my speedometer?
When your speedometer reads 60 mph with 355/45R19 fitted (calibrated for 355/40R19), your real speed is 62.8 mph. Your odometer will under-count miles by about 4.6%.
Will 355/45R19 lift my vehicle?
Ride height changes by half the diameter difference: +0.70 inches of ground clearance at the axle.

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