Tire Size Box

275/40R19 vs 275/45R19

275/45R19 compared with 275/40R19

+3.9% diameter, 0.0" width

275/45R19 is 28.74" tall vs 27.66". More than the 3% rule of thumb, so check carefully before switching.

27.7"19" rim4.3"10.8" wide
275/40R19 (solid) compared with 275/45R19 (dashed outline), drawn to scale

With 275/45R19 tires, when your speedometer says 60 mph you are really going

62.3 mph

275/45R19 is +1.08 inches (+3.9%) in overall diameter. That is more than the 3% most shops and makers recommend.

275/40R19275/45R19Difference%
Overall diameter27.66"28.74"+1.08"+3.9%
Section width10.83"10.83"0.00"0.0%
Sidewall height4.33"4.87"+0.54"+12.5%
Circumference86.90"90.30"+3.40"+3.9%
Revolutions per mile729.1701.6−27.5−3.8%

Speedometer difference

If your vehicle came with 275/40R19 and you fit 275/45R19, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.8 mph+0.8 mph
30 mph31.2 mph+1.2 mph
40 mph41.6 mph+1.6 mph
50 mph52.0 mph+2.0 mph
60 mph62.3 mph+2.3 mph
65 mph67.5 mph+2.5 mph
70 mph72.7 mph+2.7 mph
75 mph77.9 mph+2.9 mph
80 mph83.1 mph+3.1 mph

Each size on its own

Questions

Which is bigger, 275/40R19 or 275/45R19?
275/45R19 is taller by 1.08 inches (28.74" vs 27.66"). 275/40R19 is the same width.
Can I replace 275/40R19 with 275/45R19?
It is not recommended without checking carefully. The diameter difference is +3.9%, 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 275/45R19 change my speedometer?
When your speedometer reads 60 mph with 275/45R19 fitted (calibrated for 275/40R19), your real speed is 62.3 mph. Your odometer will under-count miles by about 3.9%.
Will 275/45R19 lift my vehicle?
Ride height changes by half the diameter difference: +0.54 inches of ground clearance at the axle.

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