Tire Size Box

335/40R18 vs 335/45R18

335/45R18 compared with 335/40R18

+4.6% diameter, 0.0" width

335/45R18 is 29.87" tall vs 28.55". More than the 3% rule of thumb, so check carefully before switching.

28.6"18" rim5.3"13.2" wide
335/40R18 (solid) compared with 335/45R18 (dashed outline), drawn to scale

With 335/45R18 tires, when your speedometer says 60 mph you are really going

62.8 mph

335/45R18 is +1.32 inches (+4.6%) in overall diameter. That is more than the 3% most shops and makers recommend.

335/40R18335/45R18Difference%
Overall diameter28.55"29.87"+1.32"+4.6%
Section width13.19"13.19"0.00"0.0%
Sidewall height5.28"5.94"+0.66"+12.5%
Circumference89.70"93.84"+4.14"+4.6%
Revolutions per mile706.4675.2−31.2−4.4%

Speedometer difference

If your vehicle came with 335/40R18 and you fit 335/45R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.9 mph+0.9 mph
30 mph31.4 mph+1.4 mph
40 mph41.8 mph+1.8 mph
50 mph52.3 mph+2.3 mph
60 mph62.8 mph+2.8 mph
65 mph68.0 mph+3.0 mph
70 mph73.2 mph+3.2 mph
75 mph78.5 mph+3.5 mph
80 mph83.7 mph+3.7 mph

Each size on its own

Questions

Which is bigger, 335/40R18 or 335/45R18?
335/45R18 is taller by 1.32 inches (29.87" vs 28.55"). 335/40R18 is the same width.
Can I replace 335/40R18 with 335/45R18?
It is not recommended without checking carefully. The diameter difference is +4.6%, 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 335/45R18 change my speedometer?
When your speedometer reads 60 mph with 335/45R18 fitted (calibrated for 335/40R18), your real speed is 62.8 mph. Your odometer will under-count miles by about 4.6%.
Will 335/45R18 lift my vehicle?
Ride height changes by half the diameter difference: +0.66 inches of ground clearance at the axle.

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