Tire Size Box

215/35R18 vs 215/45R18

215/45R18 compared with 215/35R18

+7.1% diameter, 0.0" width

215/45R18 is 25.62" tall vs 23.93". More than the 3% rule of thumb, so check carefully before switching.

23.9"18" rim3.0"8.5" wide
215/35R18 (solid) compared with 215/45R18 (dashed outline), drawn to scale

With 215/45R18 tires, when your speedometer says 60 mph you are really going

64.2 mph

215/45R18 is +1.69 inches (+7.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

215/35R18215/45R18Difference%
Overall diameter23.93"25.62"+1.69"+7.1%
Section width8.46"8.46"0.00"0.0%
Sidewall height2.96"3.81"+0.85"+28.6%
Circumference75.16"80.48"+5.32"+7.1%
Revolutions per mile843.0787.3−55.7−6.6%

Speedometer difference

If your vehicle came with 215/35R18 and you fit 215/45R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.4 mph+1.4 mph
30 mph32.1 mph+2.1 mph
40 mph42.8 mph+2.8 mph
50 mph53.5 mph+3.5 mph
60 mph64.2 mph+4.2 mph
65 mph69.6 mph+4.6 mph
70 mph75.0 mph+5.0 mph
75 mph80.3 mph+5.3 mph
80 mph85.7 mph+5.7 mph

Each size on its own

Questions

Which is bigger, 215/35R18 or 215/45R18?
215/45R18 is taller by 1.69 inches (25.62" vs 23.93"). 215/35R18 is the same width.
Can I replace 215/35R18 with 215/45R18?
It is not recommended without checking carefully. The diameter difference is +7.1%, 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 215/45R18 change my speedometer?
When your speedometer reads 60 mph with 215/45R18 fitted (calibrated for 215/35R18), your real speed is 64.2 mph. Your odometer will under-count miles by about 7.1%.
Will 215/45R18 lift my vehicle?
Ride height changes by half the diameter difference: +0.85 inches of ground clearance at the axle.

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