Tire Size Box

285/45R21 vs 265/50R21

265/50R21 compared with 285/45R21

+1.1% diameter, −0.8" width

265/50R21 is 31.43" tall vs 31.10". Within the 3% rule, so usually interchangeable.

31.1"21" rim5.0"11.2" wide
285/45R21 (solid) compared with 265/50R21 (dashed outline), drawn to scale

With 265/50R21 tires, when your speedometer says 60 mph you are really going

60.6 mph

265/50R21 is +0.33 inches (+1.1%) in overall diameter. That is within the 3% most shops and makers allow.

285/45R21265/50R21Difference%
Overall diameter31.10"31.43"+0.33"+1.1%
Section width11.22"10.43"−0.79"−7.0%
Sidewall height5.05"5.22"+0.17"+3.3%
Circumference97.70"98.75"+1.05"+1.1%
Revolutions per mile648.5641.6−6.9−1.1%

Speedometer difference

If your vehicle came with 285/45R21 and you fit 265/50R21, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.2 mph+0.2 mph
30 mph30.3 mph+0.3 mph
40 mph40.4 mph+0.4 mph
50 mph50.5 mph+0.5 mph
60 mph60.6 mph+0.6 mph
65 mph65.7 mph+0.7 mph
70 mph70.8 mph+0.8 mph
75 mph75.8 mph+0.8 mph
80 mph80.9 mph+0.9 mph

Each size on its own

Questions

Which is bigger, 285/45R21 or 265/50R21?
265/50R21 is taller by 0.33 inches (31.43" vs 31.10"). 285/45R21 is wider by 0.79 inches.
Can I replace 285/45R21 with 265/50R21?
Usually, yes. The diameter difference is +1.1%, inside the 3% rule of thumb most tire shops use. Check that the wider or taller tire clears your suspension and fenders, and that its load index meets your placard.
How much will 265/50R21 change my speedometer?
When your speedometer reads 60 mph with 265/50R21 fitted (calibrated for 285/45R21), your real speed is 60.6 mph. Your odometer will under-count miles by about 1.1%.
Will 265/50R21 lift my vehicle?
Ride height changes by half the diameter difference: +0.17 inches of ground clearance at the axle.

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