Tire Size Box

215/45R20 vs 215/55R20

215/55R20 compared with 215/45R20

+6.1% diameter, 0.0" width

215/55R20 is 29.31" tall vs 27.62". More than the 3% rule of thumb, so check carefully before switching.

27.6"20" rim3.8"8.5" wide
215/45R20 (solid) compared with 215/55R20 (dashed outline), drawn to scale

With 215/55R20 tires, when your speedometer says 60 mph you are really going

63.7 mph

215/55R20 is +1.69 inches (+6.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

215/45R20215/55R20Difference%
Overall diameter27.62"29.31"+1.69"+6.1%
Section width8.46"8.46"0.00"0.0%
Sidewall height3.81"4.66"+0.85"+22.2%
Circumference86.76"92.08"+5.32"+6.1%
Revolutions per mile730.2688.1−42.2−5.8%

Speedometer difference

If your vehicle came with 215/45R20 and you fit 215/55R20, 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, 215/45R20 or 215/55R20?
215/55R20 is taller by 1.69 inches (29.31" vs 27.62"). 215/45R20 is the same width.
Can I replace 215/45R20 with 215/55R20?
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 215/55R20 change my speedometer?
When your speedometer reads 60 mph with 215/55R20 fitted (calibrated for 215/45R20), your real speed is 63.7 mph. Your odometer will under-count miles by about 6.1%.
Will 215/55R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.85 inches of ground clearance at the axle.

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