Tire Size Box

265/55R20 vs 265/65R20

265/65R20 compared with 265/55R20

+6.6% diameter, 0.0" width

265/65R20 is 33.56" tall vs 31.48". More than the 3% rule of thumb, so check carefully before switching.

31.5"20" rim5.7"10.4" wide
265/55R20 (solid) compared with 265/65R20 (dashed outline), drawn to scale

With 265/65R20 tires, when your speedometer says 60 mph you are really going

64.0 mph

265/65R20 is +2.09 inches (+6.6%) in overall diameter. That is more than the 3% most shops and makers recommend.

265/55R20265/65R20Difference%
Overall diameter31.48"33.56"+2.09"+6.6%
Section width10.43"10.43"0.00"0.0%
Sidewall height5.74"6.78"+1.04"+18.2%
Circumference98.89"105.44"+6.56"+6.6%
Revolutions per mile640.7600.9−39.8−6.2%

Speedometer difference

If your vehicle came with 265/55R20 and you fit 265/65R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.3 mph+1.3 mph
30 mph32.0 mph+2.0 mph
40 mph42.7 mph+2.7 mph
50 mph53.3 mph+3.3 mph
60 mph64.0 mph+4.0 mph
65 mph69.3 mph+4.3 mph
70 mph74.6 mph+4.6 mph
75 mph80.0 mph+5.0 mph
80 mph85.3 mph+5.3 mph

Each size on its own

Questions

Which is bigger, 265/55R20 or 265/65R20?
265/65R20 is taller by 2.09 inches (33.56" vs 31.48"). 265/55R20 is the same width.
Can I replace 265/55R20 with 265/65R20?
It is not recommended without checking carefully. The diameter difference is +6.6%, 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 265/65R20 change my speedometer?
When your speedometer reads 60 mph with 265/65R20 fitted (calibrated for 265/55R20), your real speed is 64.0 mph. Your odometer will under-count miles by about 6.6%.
Will 265/65R20 lift my vehicle?
Ride height changes by half the diameter difference: +1.04 inches of ground clearance at the axle.

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