Tire Size Box

205/65R18 vs 205/75R18

205/75R18 compared with 205/65R18

+5.7% diameter, 0.0" width

205/75R18 is 30.11" tall vs 28.49". More than the 3% rule of thumb, so check carefully before switching.

28.5"18" rim5.2"8.1" wide
205/65R18 (solid) compared with 205/75R18 (dashed outline), drawn to scale

With 205/75R18 tires, when your speedometer says 60 mph you are really going

63.4 mph

205/75R18 is +1.61 inches (+5.7%) in overall diameter. That is more than the 3% most shops and makers recommend.

205/65R18205/75R18Difference%
Overall diameter28.49"30.11"+1.61"+5.7%
Section width8.07"8.07"0.00"0.0%
Sidewall height5.25"6.05"+0.81"+15.4%
Circumference89.51"94.58"+5.07"+5.7%
Revolutions per mile707.8669.9−38.0−5.4%

Speedometer difference

If your vehicle came with 205/65R18 and you fit 205/75R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.1 mph+1.1 mph
30 mph31.7 mph+1.7 mph
40 mph42.3 mph+2.3 mph
50 mph52.8 mph+2.8 mph
60 mph63.4 mph+3.4 mph
65 mph68.7 mph+3.7 mph
70 mph74.0 mph+4.0 mph
75 mph79.2 mph+4.2 mph
80 mph84.5 mph+4.5 mph

Each size on its own

Questions

Which is bigger, 205/65R18 or 205/75R18?
205/75R18 is taller by 1.61 inches (30.11" vs 28.49"). 205/65R18 is the same width.
Can I replace 205/65R18 with 205/75R18?
It is not recommended without checking carefully. The diameter difference is +5.7%, 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 205/75R18 change my speedometer?
When your speedometer reads 60 mph with 205/75R18 fitted (calibrated for 205/65R18), your real speed is 63.4 mph. Your odometer will under-count miles by about 5.7%.
Will 205/75R18 lift my vehicle?
Ride height changes by half the diameter difference: +0.81 inches of ground clearance at the axle.

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