Tire Size Box

275/25R21 vs 265/30R21

265/30R21 compared with 275/25R21

+3.2% diameter, −0.4" width

265/30R21 is 27.26" tall vs 26.41". More than the 3% rule of thumb, so check carefully before switching.

26.4"21" rim2.7"10.8" wide
275/25R21 (solid) compared with 265/30R21 (dashed outline), drawn to scale

With 265/30R21 tires, when your speedometer says 60 mph you are really going

61.9 mph

265/30R21 is +0.85 inches (+3.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

275/25R21265/30R21Difference%
Overall diameter26.41"27.26"+0.85"+3.2%
Section width10.83"10.43"−0.39"−3.6%
Sidewall height2.71"3.13"+0.42"+15.6%
Circumference82.98"85.64"+2.66"+3.2%
Revolutions per mile763.6739.8−23.7−3.1%

Speedometer difference

If your vehicle came with 275/25R21 and you fit 265/30R21, 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 mph72.2 mph+2.2 mph
75 mph77.4 mph+2.4 mph
80 mph82.6 mph+2.6 mph

Each size on its own

Questions

Which is bigger, 275/25R21 or 265/30R21?
265/30R21 is taller by 0.85 inches (27.26" vs 26.41"). 275/25R21 is wider by 0.39 inches.
Can I replace 275/25R21 with 265/30R21?
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 265/30R21 change my speedometer?
When your speedometer reads 60 mph with 265/30R21 fitted (calibrated for 275/25R21), your real speed is 61.9 mph. Your odometer will under-count miles by about 3.2%.
Will 265/30R21 lift my vehicle?
Ride height changes by half the diameter difference: +0.42 inches of ground clearance at the axle.

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