Tire Size Box

215/40R17 vs 215/45R17

215/45R17 compared with 215/40R17

+3.6% diameter, 0.0" width

215/45R17 is 24.62" tall vs 23.77". More than the 3% rule of thumb, so check carefully before switching.

23.8"17" rim3.4"8.5" wide
215/40R17 (solid) compared with 215/45R17 (dashed outline), drawn to scale

With 215/45R17 tires, when your speedometer says 60 mph you are really going

62.1 mph

215/45R17 is +0.85 inches (+3.6%) in overall diameter. That is more than the 3% most shops and makers recommend.

215/40R17215/45R17Difference%
Overall diameter23.77"24.62"+0.85"+3.6%
Section width8.46"8.46"0.00"0.0%
Sidewall height3.39"3.81"+0.42"+12.5%
Circumference74.68"77.34"+2.66"+3.6%
Revolutions per mile848.4819.2−29.2−3.4%

Speedometer difference

If your vehicle came with 215/40R17 and you fit 215/45R17, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.1 mph+1.1 mph
40 mph41.4 mph+1.4 mph
50 mph51.8 mph+1.8 mph
60 mph62.1 mph+2.1 mph
65 mph67.3 mph+2.3 mph
70 mph72.5 mph+2.5 mph
75 mph77.7 mph+2.7 mph
80 mph82.8 mph+2.8 mph

Each size on its own

Questions

Which is bigger, 215/40R17 or 215/45R17?
215/45R17 is taller by 0.85 inches (24.62" vs 23.77"). 215/40R17 is the same width.
Can I replace 215/40R17 with 215/45R17?
It is not recommended without checking carefully. The diameter difference is +3.6%, 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 215/45R17 change my speedometer?
When your speedometer reads 60 mph with 215/45R17 fitted (calibrated for 215/40R17), your real speed is 62.1 mph. Your odometer will under-count miles by about 3.6%.
Will 215/45R17 lift my vehicle?
Ride height changes by half the diameter difference: +0.42 inches of ground clearance at the axle.

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