Tire Size Box

245/55R18 vs 265/55R18

265/55R18 compared with 245/55R18

+3.0% diameter, +0.8" width

265/55R18 is 29.48" tall vs 28.61". More than the 3% rule of thumb, so check carefully before switching.

28.6"18" rim5.3"9.6" wide
245/55R18 (solid) compared with 265/55R18 (dashed outline), drawn to scale

With 265/55R18 tires, when your speedometer says 60 mph you are really going

61.8 mph

265/55R18 is +0.87 inches (+3.0%) in overall diameter. That is more than the 3% most shops and makers recommend.

245/55R18265/55R18Difference%
Overall diameter28.61"29.48"+0.87"+3.0%
Section width9.65"10.43"+0.79"+8.2%
Sidewall height5.31"5.74"+0.43"+8.2%
Circumference89.88"92.60"+2.72"+3.0%
Revolutions per mile704.9684.2−20.7−2.9%

Speedometer difference

If your vehicle came with 245/55R18 and you fit 265/55R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.6 mph+0.6 mph
30 mph30.9 mph+0.9 mph
40 mph41.2 mph+1.2 mph
50 mph51.5 mph+1.5 mph
60 mph61.8 mph+1.8 mph
65 mph67.0 mph+2.0 mph
70 mph72.1 mph+2.1 mph
75 mph77.3 mph+2.3 mph
80 mph82.4 mph+2.4 mph

Each size on its own

Questions

Which is bigger, 245/55R18 or 265/55R18?
265/55R18 is taller by 0.87 inches (29.48" vs 28.61"). 265/55R18 is wider by 0.79 inches.
Can I replace 245/55R18 with 265/55R18?
It is not recommended without checking carefully. The diameter difference is +3.0%, 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 265/55R18 change my speedometer?
When your speedometer reads 60 mph with 265/55R18 fitted (calibrated for 245/55R18), your real speed is 61.8 mph. Your odometer will under-count miles by about 3.0%.
Will 265/55R18 lift my vehicle?
Ride height changes by half the diameter difference: +0.43 inches of ground clearance at the axle.

Other comparisons