Tire Size Box

215/55R18 vs 215/65R18

215/65R18 compared with 215/55R18

+6.2% diameter, 0.0" width

215/65R18 is 29.00" tall vs 27.31". More than the 3% rule of thumb, so check carefully before switching.

27.3"18" rim4.7"8.5" wide
215/55R18 (solid) compared with 215/65R18 (dashed outline), drawn to scale

With 215/65R18 tires, when your speedometer says 60 mph you are really going

63.7 mph

215/65R18 is +1.69 inches (+6.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

215/55R18215/65R18Difference%
Overall diameter27.31"29.00"+1.69"+6.2%
Section width8.46"8.46"0.00"0.0%
Sidewall height4.66"5.50"+0.85"+18.2%
Circumference85.80"91.12"+5.32"+6.2%
Revolutions per mile738.5695.4−43.1−5.8%

Speedometer difference

If your vehicle came with 215/55R18 and you fit 215/65R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.2 mph+1.2 mph
30 mph31.9 mph+1.9 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 mph85.0 mph+5.0 mph

Each size on its own

Questions

Which is bigger, 215/55R18 or 215/65R18?
215/65R18 is taller by 1.69 inches (29.00" vs 27.31"). 215/55R18 is the same width.
Can I replace 215/55R18 with 215/65R18?
It is not recommended without checking carefully. The diameter difference is +6.2%, 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 215/65R18 change my speedometer?
When your speedometer reads 60 mph with 215/65R18 fitted (calibrated for 215/55R18), your real speed is 63.7 mph. Your odometer will under-count miles by about 6.2%.
Will 215/65R18 lift my vehicle?
Ride height changes by half the diameter difference: +0.85 inches of ground clearance at the axle.

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