Tire Size Box

175/55R15 vs 175/65R15

175/65R15 compared with 175/55R15

+6.1% diameter, 0.0" width

175/65R15 is 23.96" tall vs 22.58". More than the 3% rule of thumb, so check carefully before switching.

22.6"15" rim3.8"6.9" wide
175/55R15 (solid) compared with 175/65R15 (dashed outline), drawn to scale

With 175/65R15 tires, when your speedometer says 60 mph you are really going

63.7 mph

175/65R15 is +1.38 inches (+6.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

175/55R15175/65R15Difference%
Overall diameter22.58"23.96"+1.38"+6.1%
Section width6.89"6.89"0.00"0.0%
Sidewall height3.79"4.48"+0.69"+18.2%
Circumference70.93"75.26"+4.33"+6.1%
Revolutions per mile893.2841.9−51.4−5.8%

Speedometer difference

If your vehicle came with 175/55R15 and you fit 175/65R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.2 mph+1.2 mph
30 mph31.8 mph+1.8 mph
40 mph42.4 mph+2.4 mph
50 mph53.1 mph+3.1 mph
60 mph63.7 mph+3.7 mph
65 mph69.0 mph+4.0 mph
70 mph74.3 mph+4.3 mph
75 mph79.6 mph+4.6 mph
80 mph84.9 mph+4.9 mph

Each size on its own

Questions

Which is bigger, 175/55R15 or 175/65R15?
175/65R15 is taller by 1.38 inches (23.96" vs 22.58"). 175/55R15 is the same width.
Can I replace 175/55R15 with 175/65R15?
It is not recommended without checking carefully. The diameter difference is +6.1%, 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 175/65R15 change my speedometer?
When your speedometer reads 60 mph with 175/65R15 fitted (calibrated for 175/55R15), your real speed is 63.7 mph. Your odometer will under-count miles by about 6.1%.
Will 175/65R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.69 inches of ground clearance at the axle.

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