Tire Size Box

295/40R20 vs 295/45R20

295/45R20 compared with 295/40R20

+4.0% diameter, 0.0" width

295/45R20 is 30.45" tall vs 29.29". More than the 3% rule of thumb, so check carefully before switching.

29.3"20" rim4.6"11.6" wide
295/40R20 (solid) compared with 295/45R20 (dashed outline), drawn to scale

With 295/45R20 tires, when your speedometer says 60 mph you are really going

62.4 mph

295/45R20 is +1.16 inches (+4.0%) in overall diameter. That is more than the 3% most shops and makers recommend.

295/40R20295/45R20Difference%
Overall diameter29.29"30.45"+1.16"+4.0%
Section width11.61"11.61"0.00"0.0%
Sidewall height4.65"5.23"+0.58"+12.5%
Circumference92.02"95.67"+3.65"+4.0%
Revolutions per mile688.5662.3−26.3−3.8%

Speedometer difference

If your vehicle came with 295/40R20 and you fit 295/45R20, 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 mph62.4 mph+2.4 mph
65 mph67.6 mph+2.6 mph
70 mph72.8 mph+2.8 mph
75 mph78.0 mph+3.0 mph
80 mph83.2 mph+3.2 mph

Each size on its own

Questions

Which is bigger, 295/40R20 or 295/45R20?
295/45R20 is taller by 1.16 inches (30.45" vs 29.29"). 295/40R20 is the same width.
Can I replace 295/40R20 with 295/45R20?
It is not recommended without checking carefully. The diameter difference is +4.0%, 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 295/45R20 change my speedometer?
When your speedometer reads 60 mph with 295/45R20 fitted (calibrated for 295/40R20), your real speed is 62.4 mph. Your odometer will under-count miles by about 4.0%.
Will 295/45R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.58 inches of ground clearance at the axle.

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