Tire Size Box

175/65R15 vs 175/75R15

175/75R15 compared with 175/65R15

+5.8% diameter, 0.0" width

175/75R15 is 25.33" tall vs 23.96". More than the 3% rule of thumb, so check carefully before switching.

24.0"15" rim4.5"6.9" wide
175/65R15 (solid) compared with 175/75R15 (dashed outline), drawn to scale

With 175/75R15 tires, when your speedometer says 60 mph you are really going

63.5 mph

175/75R15 is +1.38 inches (+5.8%) in overall diameter. That is more than the 3% most shops and makers recommend.

175/65R15175/75R15Difference%
Overall diameter23.96"25.33"+1.38"+5.8%
Section width6.89"6.89"0.00"0.0%
Sidewall height4.48"5.17"+0.69"+15.4%
Circumference75.26"79.59"+4.33"+5.8%
Revolutions per mile841.9796.1−45.8−5.4%

Speedometer difference

If your vehicle came with 175/65R15 and you fit 175/75R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.2 mph+1.2 mph
30 mph31.7 mph+1.7 mph
40 mph42.3 mph+2.3 mph
50 mph52.9 mph+2.9 mph
60 mph63.5 mph+3.5 mph
65 mph68.7 mph+3.7 mph
70 mph74.0 mph+4.0 mph
75 mph79.3 mph+4.3 mph
80 mph84.6 mph+4.6 mph

Each size on its own

Questions

Which is bigger, 175/65R15 or 175/75R15?
175/75R15 is taller by 1.38 inches (25.33" vs 23.96"). 175/65R15 is the same width.
Can I replace 175/65R15 with 175/75R15?
It is not recommended without checking carefully. The diameter difference is +5.8%, 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 175/75R15 change my speedometer?
When your speedometer reads 60 mph with 175/75R15 fitted (calibrated for 175/65R15), your real speed is 63.5 mph. Your odometer will under-count miles by about 5.8%.
Will 175/75R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.69 inches of ground clearance at the axle.

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