Tire Size Box

225/45R21 vs 225/50R21

225/50R21 compared with 225/45R21

+3.1% diameter, 0.0" width

225/50R21 is 29.86" tall vs 28.97". More than the 3% rule of thumb, so check carefully before switching.

29.0"21" rim4.0"8.9" wide
225/45R21 (solid) compared with 225/50R21 (dashed outline), drawn to scale

With 225/50R21 tires, when your speedometer says 60 mph you are really going

61.8 mph

225/50R21 is +0.89 inches (+3.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

225/45R21225/50R21Difference%
Overall diameter28.97"29.86"+0.89"+3.1%
Section width8.86"8.86"0.00"0.0%
Sidewall height3.99"4.43"+0.44"+11.1%
Circumference91.02"93.80"+2.78"+3.1%
Revolutions per mile696.1675.5−20.7−3.0%

Speedometer difference

If your vehicle came with 225/45R21 and you fit 225/50R21, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.6 mph+0.6 mph
30 mph30.9 mph+0.9 mph
40 mph41.2 mph+1.2 mph
50 mph51.5 mph+1.5 mph
60 mph61.8 mph+1.8 mph
65 mph67.0 mph+2.0 mph
70 mph72.1 mph+2.1 mph
75 mph77.3 mph+2.3 mph
80 mph82.4 mph+2.4 mph

Each size on its own

Questions

Which is bigger, 225/45R21 or 225/50R21?
225/50R21 is taller by 0.89 inches (29.86" vs 28.97"). 225/45R21 is the same width.
Can I replace 225/45R21 with 225/50R21?
It is not recommended without checking carefully. The diameter difference is +3.1%, 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 225/50R21 change my speedometer?
When your speedometer reads 60 mph with 225/50R21 fitted (calibrated for 225/45R21), your real speed is 61.8 mph. Your odometer will under-count miles by about 3.1%.
Will 225/50R21 lift my vehicle?
Ride height changes by half the diameter difference: +0.44 inches of ground clearance at the axle.

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