Tire Size Box

285/60R18 vs 285/70R18

285/70R18 compared with 285/60R18

+7.1% diameter, 0.0" width

285/70R18 is 33.71" tall vs 31.46". More than the 3% rule of thumb, so check carefully before switching.

31.5"18" rim6.7"11.2" wide
285/60R18 (solid) compared with 285/70R18 (dashed outline), drawn to scale

With 285/70R18 tires, when your speedometer says 60 mph you are really going

64.3 mph

285/70R18 is +2.24 inches (+7.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

285/60R18285/70R18Difference%
Overall diameter31.46"33.71"+2.24"+7.1%
Section width11.22"11.22"0.00"0.0%
Sidewall height6.73"7.85"+1.12"+16.7%
Circumference98.85"105.90"+7.05"+7.1%
Revolutions per mile641.0598.3−42.7−6.7%

Speedometer difference

If your vehicle came with 285/60R18 and you fit 285/70R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.4 mph+1.4 mph
30 mph32.1 mph+2.1 mph
40 mph42.9 mph+2.9 mph
50 mph53.6 mph+3.6 mph
60 mph64.3 mph+4.3 mph
65 mph69.6 mph+4.6 mph
70 mph75.0 mph+5.0 mph
75 mph80.3 mph+5.3 mph
80 mph85.7 mph+5.7 mph

Each size on its own

Questions

Which is bigger, 285/60R18 or 285/70R18?
285/70R18 is taller by 2.24 inches (33.71" vs 31.46"). 285/60R18 is the same width.
Can I replace 285/60R18 with 285/70R18?
It is not recommended without checking carefully. The diameter difference is +7.1%, 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 285/70R18 change my speedometer?
When your speedometer reads 60 mph with 285/70R18 fitted (calibrated for 285/60R18), your real speed is 64.3 mph. Your odometer will under-count miles by about 7.1%.
Will 285/70R18 lift my vehicle?
Ride height changes by half the diameter difference: +1.12 inches of ground clearance at the axle.

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