Tire Size Box

275/45R21 vs 275/50R21

275/50R21 compared with 275/45R21

+3.5% diameter, 0.0" width

275/50R21 is 31.83" tall vs 30.74". More than the 3% rule of thumb, so check carefully before switching.

30.7"21" rim4.9"10.8" wide
275/45R21 (solid) compared with 275/50R21 (dashed outline), drawn to scale

With 275/50R21 tires, when your speedometer says 60 mph you are really going

62.1 mph

275/50R21 is +1.08 inches (+3.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

275/45R21275/50R21Difference%
Overall diameter30.74"31.83"+1.08"+3.5%
Section width10.83"10.83"0.00"0.0%
Sidewall height4.87"5.41"+0.54"+11.1%
Circumference96.59"99.99"+3.40"+3.5%
Revolutions per mile656.0633.7−22.3−3.4%

Speedometer difference

If your vehicle came with 275/45R21 and you fit 275/50R21, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.1 mph+1.1 mph
40 mph41.4 mph+1.4 mph
50 mph51.8 mph+1.8 mph
60 mph62.1 mph+2.1 mph
65 mph67.3 mph+2.3 mph
70 mph72.5 mph+2.5 mph
75 mph77.6 mph+2.6 mph
80 mph82.8 mph+2.8 mph

Each size on its own

Questions

Which is bigger, 275/45R21 or 275/50R21?
275/50R21 is taller by 1.08 inches (31.83" vs 30.74"). 275/45R21 is the same width.
Can I replace 275/45R21 with 275/50R21?
It is not recommended without checking carefully. The diameter difference is +3.5%, 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 275/50R21 change my speedometer?
When your speedometer reads 60 mph with 275/50R21 fitted (calibrated for 275/45R21), your real speed is 62.1 mph. Your odometer will under-count miles by about 3.5%.
Will 275/50R21 lift my vehicle?
Ride height changes by half the diameter difference: +0.54 inches of ground clearance at the axle.

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