Tire Size Box

225/40R16 vs 225/45R16

225/45R16 compared with 225/40R16

+3.8% diameter, 0.0" width

225/45R16 is 23.97" tall vs 23.09". More than the 3% rule of thumb, so check carefully before switching.

23.1"16" rim3.5"8.9" wide
225/40R16 (solid) compared with 225/45R16 (dashed outline), drawn to scale

With 225/45R16 tires, when your speedometer says 60 mph you are really going

62.3 mph

225/45R16 is +0.89 inches (+3.8%) in overall diameter. That is more than the 3% most shops and makers recommend.

225/40R16225/45R16Difference%
Overall diameter23.09"23.97"+0.89"+3.8%
Section width8.86"8.86"0.00"0.0%
Sidewall height3.54"3.99"+0.44"+12.5%
Circumference72.53"75.31"+2.78"+3.8%
Revolutions per mile873.6841.3−32.3−3.7%

Speedometer difference

If your vehicle came with 225/40R16 and you fit 225/45R16, 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 mph41.5 mph+1.5 mph
50 mph51.9 mph+1.9 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, 225/40R16 or 225/45R16?
225/45R16 is taller by 0.89 inches (23.97" vs 23.09"). 225/40R16 is the same width.
Can I replace 225/40R16 with 225/45R16?
It is not recommended without checking carefully. The diameter difference is +3.8%, 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 225/45R16 change my speedometer?
When your speedometer reads 60 mph with 225/45R16 fitted (calibrated for 225/40R16), your real speed is 62.3 mph. Your odometer will under-count miles by about 3.8%.
Will 225/45R16 lift my vehicle?
Ride height changes by half the diameter difference: +0.44 inches of ground clearance at the axle.

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