Tire Size Box

185/60R15 vs 185/70R15

185/70R15 compared with 185/60R15

+6.1% diameter, 0.0" width

185/70R15 is 25.20" tall vs 23.74". More than the 3% rule of thumb, so check carefully before switching.

23.7"15" rim4.4"7.3" wide
185/60R15 (solid) compared with 185/70R15 (dashed outline), drawn to scale

With 185/70R15 tires, when your speedometer says 60 mph you are really going

63.7 mph

185/70R15 is +1.46 inches (+6.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

185/60R15185/70R15Difference%
Overall diameter23.74"25.20"+1.46"+6.1%
Section width7.28"7.28"0.00"0.0%
Sidewall height4.37"5.10"+0.73"+16.7%
Circumference74.58"79.16"+4.58"+6.1%
Revolutions per mile849.5800.4−49.1−5.8%

Speedometer difference

If your vehicle came with 185/60R15 and you fit 185/70R15, 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 mph42.5 mph+2.5 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, 185/60R15 or 185/70R15?
185/70R15 is taller by 1.46 inches (25.20" vs 23.74"). 185/60R15 is the same width.
Can I replace 185/60R15 with 185/70R15?
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 185/70R15 change my speedometer?
When your speedometer reads 60 mph with 185/70R15 fitted (calibrated for 185/60R15), your real speed is 63.7 mph. Your odometer will under-count miles by about 6.1%.
Will 185/70R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.73 inches of ground clearance at the axle.

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