Tire Size Box

315/60R18 vs 315/65R18

315/65R18 compared with 315/60R18

+3.8% diameter, 0.0" width

315/65R18 is 34.12" tall vs 32.88". More than the 3% rule of thumb, so check carefully before switching.

32.9"18" rim7.4"12.4" wide
315/60R18 (solid) compared with 315/65R18 (dashed outline), drawn to scale

With 315/65R18 tires, when your speedometer says 60 mph you are really going

62.3 mph

315/65R18 is +1.24 inches (+3.8%) in overall diameter. That is more than the 3% most shops and makers recommend.

315/60R18315/65R18Difference%
Overall diameter32.88"34.12"+1.24"+3.8%
Section width12.40"12.40"0.00"0.0%
Sidewall height7.44"8.06"+0.62"+8.3%
Circumference103.30"107.20"+3.90"+3.8%
Revolutions per mile613.4591.1−22.3−3.6%

Speedometer difference

If your vehicle came with 315/60R18 and you fit 315/65R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.8 mph+0.8 mph
30 mph31.1 mph+1.1 mph
40 mph41.5 mph+1.5 mph
50 mph51.9 mph+1.9 mph
60 mph62.3 mph+2.3 mph
65 mph67.5 mph+2.5 mph
70 mph72.6 mph+2.6 mph
75 mph77.8 mph+2.8 mph
80 mph83.0 mph+3.0 mph

Each size on its own

Questions

Which is bigger, 315/60R18 or 315/65R18?
315/65R18 is taller by 1.24 inches (34.12" vs 32.88"). 315/60R18 is the same width.
Can I replace 315/60R18 with 315/65R18?
It is not recommended without checking carefully. The diameter difference is +3.8%, 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 315/65R18 change my speedometer?
When your speedometer reads 60 mph with 315/65R18 fitted (calibrated for 315/60R18), your real speed is 62.3 mph. Your odometer will under-count miles by about 3.8%.
Will 315/65R18 lift my vehicle?
Ride height changes by half the diameter difference: +0.62 inches of ground clearance at the axle.

Other comparisons