Tire Size Box

225/40R20 vs 225/50R20

225/50R20 compared with 225/40R20

+6.5% diameter, 0.0" width

225/50R20 is 28.86" tall vs 27.09". More than the 3% rule of thumb, so check carefully before switching.

27.1"20" rim3.5"8.9" wide
225/40R20 (solid) compared with 225/50R20 (dashed outline), drawn to scale

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

63.9 mph

225/50R20 is +1.77 inches (+6.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

225/40R20225/50R20Difference%
Overall diameter27.09"28.86"+1.77"+6.5%
Section width8.86"8.86"0.00"0.0%
Sidewall height3.54"4.43"+0.89"+25.0%
Circumference85.10"90.66"+5.57"+6.5%
Revolutions per mile744.6698.9−45.7−6.1%

Speedometer difference

If your vehicle came with 225/40R20 and you fit 225/50R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.3 mph+1.3 mph
30 mph32.0 mph+2.0 mph
40 mph42.6 mph+2.6 mph
50 mph53.3 mph+3.3 mph
60 mph63.9 mph+3.9 mph
65 mph69.3 mph+4.3 mph
70 mph74.6 mph+4.6 mph
75 mph79.9 mph+4.9 mph
80 mph85.2 mph+5.2 mph

Each size on its own

Questions

Which is bigger, 225/40R20 or 225/50R20?
225/50R20 is taller by 1.77 inches (28.86" vs 27.09"). 225/40R20 is the same width.
Can I replace 225/40R20 with 225/50R20?
It is not recommended without checking carefully. The diameter difference is +6.5%, 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 225/40R20), your real speed is 63.9 mph. Your odometer will under-count miles by about 6.5%.
Will 225/50R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.89 inches of ground clearance at the axle.

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