Tire Size Box

265/45R21 vs 265/55R21

265/55R21 compared with 265/45R21

+6.9% diameter, 0.0" width

265/55R21 is 32.48" tall vs 30.39". More than the 3% rule of thumb, so check carefully before switching.

30.4"21" rim4.7"10.4" wide
265/45R21 (solid) compared with 265/55R21 (dashed outline), drawn to scale

With 265/55R21 tires, when your speedometer says 60 mph you are really going

64.1 mph

265/55R21 is +2.09 inches (+6.9%) in overall diameter. That is more than the 3% most shops and makers recommend.

265/45R21265/55R21Difference%
Overall diameter30.39"32.48"+2.09"+6.9%
Section width10.43"10.43"0.00"0.0%
Sidewall height4.69"5.74"+1.04"+22.2%
Circumference95.47"102.03"+6.56"+6.9%
Revolutions per mile663.6621.0−42.6−6.4%

Speedometer difference

If your vehicle came with 265/45R21 and you fit 265/55R21, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.4 mph+1.4 mph
30 mph32.1 mph+2.1 mph
40 mph42.7 mph+2.7 mph
50 mph53.4 mph+3.4 mph
60 mph64.1 mph+4.1 mph
65 mph69.5 mph+4.5 mph
70 mph74.8 mph+4.8 mph
75 mph80.1 mph+5.1 mph
80 mph85.5 mph+5.5 mph

Each size on its own

Questions

Which is bigger, 265/45R21 or 265/55R21?
265/55R21 is taller by 2.09 inches (32.48" vs 30.39"). 265/45R21 is the same width.
Can I replace 265/45R21 with 265/55R21?
It is not recommended without checking carefully. The diameter difference is +6.9%, 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 265/55R21 change my speedometer?
When your speedometer reads 60 mph with 265/55R21 fitted (calibrated for 265/45R21), your real speed is 64.1 mph. Your odometer will under-count miles by about 6.9%.
Will 265/55R21 lift my vehicle?
Ride height changes by half the diameter difference: +1.04 inches of ground clearance at the axle.

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