Tire Size Box

275/65R15 vs 275/75R15

275/75R15 compared with 275/65R15

+7.4% diameter, 0.0" width

275/75R15 is 31.24" tall vs 29.07". More than the 3% rule of thumb, so check carefully before switching.

29.1"15" rim7.0"10.8" wide
275/65R15 (solid) compared with 275/75R15 (dashed outline), drawn to scale

With 275/75R15 tires, when your speedometer says 60 mph you are really going

64.5 mph

275/75R15 is +2.17 inches (+7.4%) in overall diameter. That is more than the 3% most shops and makers recommend.

275/65R15275/75R15Difference%
Overall diameter29.07"31.24"+2.17"+7.4%
Section width10.83"10.83"0.00"0.0%
Sidewall height7.04"8.12"+1.08"+15.4%
Circumference91.34"98.14"+6.80"+7.4%
Revolutions per mile693.7645.6−48.1−6.9%

Speedometer difference

If your vehicle came with 275/65R15 and you fit 275/75R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.5 mph+1.5 mph
30 mph32.2 mph+2.2 mph
40 mph43.0 mph+3.0 mph
50 mph53.7 mph+3.7 mph
60 mph64.5 mph+4.5 mph
65 mph69.8 mph+4.8 mph
70 mph75.2 mph+5.2 mph
75 mph80.6 mph+5.6 mph
80 mph86.0 mph+6.0 mph

Each size on its own

Questions

Which is bigger, 275/65R15 or 275/75R15?
275/75R15 is taller by 2.17 inches (31.24" vs 29.07"). 275/65R15 is the same width.
Can I replace 275/65R15 with 275/75R15?
It is not recommended without checking carefully. The diameter difference is +7.4%, 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 275/75R15 change my speedometer?
When your speedometer reads 60 mph with 275/75R15 fitted (calibrated for 275/65R15), your real speed is 64.5 mph. Your odometer will under-count miles by about 7.4%.
Will 275/75R15 lift my vehicle?
Ride height changes by half the diameter difference: +1.08 inches of ground clearance at the axle.

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