Tire Size Box

245/45R21 vs 245/50R21

245/50R21 compared with 245/45R21

+3.2% diameter, 0.0" width

245/50R21 is 30.65" tall vs 29.68". More than the 3% rule of thumb, so check carefully before switching.

29.7"21" rim4.3"9.6" wide
245/45R21 (solid) compared with 245/50R21 (dashed outline), drawn to scale

With 245/50R21 tires, when your speedometer says 60 mph you are really going

61.9 mph

245/50R21 is +0.96 inches (+3.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

245/45R21245/50R21Difference%
Overall diameter29.68"30.65"+0.96"+3.2%
Section width9.65"9.65"0.00"0.0%
Sidewall height4.34"4.82"+0.48"+11.1%
Circumference93.25"96.28"+3.03"+3.2%
Revolutions per mile679.5658.1−21.4−3.1%

Speedometer difference

If your vehicle came with 245/45R21 and you fit 245/50R21, 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 mph72.3 mph+2.3 mph
75 mph77.4 mph+2.4 mph
80 mph82.6 mph+2.6 mph

Each size on its own

Questions

Which is bigger, 245/45R21 or 245/50R21?
245/50R21 is taller by 0.96 inches (30.65" vs 29.68"). 245/45R21 is the same width.
Can I replace 245/45R21 with 245/50R21?
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 245/50R21 change my speedometer?
When your speedometer reads 60 mph with 245/50R21 fitted (calibrated for 245/45R21), your real speed is 61.9 mph. Your odometer will under-count miles by about 3.2%.
Will 245/50R21 lift my vehicle?
Ride height changes by half the diameter difference: +0.48 inches of ground clearance at the axle.

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