Tire Size Box

275/70R18 vs 275/75R18

275/75R18 compared with 275/70R18

+3.3% diameter, 0.0" width

275/75R18 is 34.24" tall vs 33.16". More than the 3% rule of thumb, so check carefully before switching.

33.2"18" rim7.6"10.8" wide
275/70R18 (solid) compared with 275/75R18 (dashed outline), drawn to scale

With 275/75R18 tires, when your speedometer says 60 mph you are really going

62.0 mph

275/75R18 is +1.08 inches (+3.3%) in overall diameter. That is more than the 3% most shops and makers recommend.

275/70R18275/75R18Difference%
Overall diameter33.16"34.24"+1.08"+3.3%
Section width10.83"10.83"0.00"0.0%
Sidewall height7.58"8.12"+0.54"+7.1%
Circumference104.17"107.57"+3.40"+3.3%
Revolutions per mile608.3589.0−19.2−3.2%

Speedometer difference

If your vehicle came with 275/70R18 and you fit 275/75R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.0 mph+1.0 mph
40 mph41.3 mph+1.3 mph
50 mph51.6 mph+1.6 mph
60 mph62.0 mph+2.0 mph
65 mph67.1 mph+2.1 mph
70 mph72.3 mph+2.3 mph
75 mph77.4 mph+2.4 mph
80 mph82.6 mph+2.6 mph

Each size on its own

Questions

Which is bigger, 275/70R18 or 275/75R18?
275/75R18 is taller by 1.08 inches (34.24" vs 33.16"). 275/70R18 is the same width.
Can I replace 275/70R18 with 275/75R18?
It is not recommended without checking carefully. The diameter difference is +3.3%, 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 275/75R18 change my speedometer?
When your speedometer reads 60 mph with 275/75R18 fitted (calibrated for 275/70R18), your real speed is 62.0 mph. Your odometer will under-count miles by about 3.3%.
Will 275/75R18 lift my vehicle?
Ride height changes by half the diameter difference: +0.54 inches of ground clearance at the axle.

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