Tire Size Box

225/45R20 vs 225/50R20

225/50R20 compared with 225/45R20

+3.2% diameter, 0.0" width

225/50R20 is 28.86" tall vs 27.97". More than the 3% rule of thumb, so check carefully before switching.

28.0"20" rim4.0"8.9" wide
225/45R20 (solid) compared with 225/50R20 (dashed outline), drawn to scale

With 225/50R20 tires, when your speedometer says 60 mph you are really going

61.9 mph

225/50R20 is +0.89 inches (+3.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

225/45R20225/50R20Difference%
Overall diameter27.97"28.86"+0.89"+3.2%
Section width8.86"8.86"0.00"0.0%
Sidewall height3.99"4.43"+0.44"+11.1%
Circumference87.88"90.66"+2.78"+3.2%
Revolutions per mile721.0698.9−22.1−3.1%

Speedometer difference

If your vehicle came with 225/45R20 and you fit 225/50R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.6 mph+0.6 mph
30 mph31.0 mph+1.0 mph
40 mph41.3 mph+1.3 mph
50 mph51.6 mph+1.6 mph
60 mph61.9 mph+1.9 mph
65 mph67.1 mph+2.1 mph
70 mph72.2 mph+2.2 mph
75 mph77.4 mph+2.4 mph
80 mph82.5 mph+2.5 mph

Each size on its own

Questions

Which is bigger, 225/45R20 or 225/50R20?
225/50R20 is taller by 0.89 inches (28.86" vs 27.97"). 225/45R20 is the same width.
Can I replace 225/45R20 with 225/50R20?
It is not recommended without checking carefully. The diameter difference is +3.2%, 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 225/50R20 change my speedometer?
When your speedometer reads 60 mph with 225/50R20 fitted (calibrated for 225/45R20), your real speed is 61.9 mph. Your odometer will under-count miles by about 3.2%.
Will 225/50R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.44 inches of ground clearance at the axle.

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