Tire Size Box

275/60R18 vs 275/70R18

275/70R18 compared with 275/60R18

+7.0% diameter, 0.0" width

275/70R18 is 33.16" tall vs 30.99". More than the 3% rule of thumb, so check carefully before switching.

31.0"18" rim6.5"10.8" wide
275/60R18 (solid) compared with 275/70R18 (dashed outline), drawn to scale

With 275/70R18 tires, when your speedometer says 60 mph you are really going

64.2 mph

275/70R18 is +2.17 inches (+7.0%) in overall diameter. That is more than the 3% most shops and makers recommend.

275/60R18275/70R18Difference%
Overall diameter30.99"33.16"+2.17"+7.0%
Section width10.83"10.83"0.00"0.0%
Sidewall height6.50"7.58"+1.08"+16.7%
Circumference97.36"104.17"+6.80"+7.0%
Revolutions per mile650.7608.3−42.5−6.5%

Speedometer difference

If your vehicle came with 275/60R18 and you fit 275/70R18, 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 mph42.8 mph+2.8 mph
50 mph53.5 mph+3.5 mph
60 mph64.2 mph+4.2 mph
65 mph69.5 mph+4.5 mph
70 mph74.9 mph+4.9 mph
75 mph80.2 mph+5.2 mph
80 mph85.6 mph+5.6 mph

Each size on its own

Questions

Which is bigger, 275/60R18 or 275/70R18?
275/70R18 is taller by 2.17 inches (33.16" vs 30.99"). 275/60R18 is the same width.
Can I replace 275/60R18 with 275/70R18?
It is not recommended without checking carefully. The diameter difference is +7.0%, 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 275/70R18 change my speedometer?
When your speedometer reads 60 mph with 275/70R18 fitted (calibrated for 275/60R18), your real speed is 64.2 mph. Your odometer will under-count miles by about 7.0%.
Will 275/70R18 lift my vehicle?
Ride height changes by half the diameter difference: +1.08 inches of ground clearance at the axle.

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