Tire Size Box

295/40R18 vs 295/45R18

295/45R18 compared with 295/40R18

+4.3% diameter, 0.0" width

295/45R18 is 28.45" tall vs 27.29". More than the 3% rule of thumb, so check carefully before switching.

27.3"18" rim4.6"11.6" wide
295/40R18 (solid) compared with 295/45R18 (dashed outline), drawn to scale

With 295/45R18 tires, when your speedometer says 60 mph you are really going

62.6 mph

295/45R18 is +1.16 inches (+4.3%) in overall diameter. That is more than the 3% most shops and makers recommend.

295/40R18295/45R18Difference%
Overall diameter27.29"28.45"+1.16"+4.3%
Section width11.61"11.61"0.00"0.0%
Sidewall height4.65"5.23"+0.58"+12.5%
Circumference85.74"89.39"+3.65"+4.3%
Revolutions per mile739.0708.8−30.2−4.1%

Speedometer difference

If your vehicle came with 295/40R18 and you fit 295/45R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.9 mph+0.9 mph
30 mph31.3 mph+1.3 mph
40 mph41.7 mph+1.7 mph
50 mph52.1 mph+2.1 mph
60 mph62.6 mph+2.6 mph
65 mph67.8 mph+2.8 mph
70 mph73.0 mph+3.0 mph
75 mph78.2 mph+3.2 mph
80 mph83.4 mph+3.4 mph

Each size on its own

Questions

Which is bigger, 295/40R18 or 295/45R18?
295/45R18 is taller by 1.16 inches (28.45" vs 27.29"). 295/40R18 is the same width.
Can I replace 295/40R18 with 295/45R18?
It is not recommended without checking carefully. The diameter difference is +4.3%, 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 295/45R18 change my speedometer?
When your speedometer reads 60 mph with 295/45R18 fitted (calibrated for 295/40R18), your real speed is 62.6 mph. Your odometer will under-count miles by about 4.3%.
Will 295/45R18 lift my vehicle?
Ride height changes by half the diameter difference: +0.58 inches of ground clearance at the axle.

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