Tire Size Box

335/40R21 vs 335/45R21

335/45R21 compared with 335/40R21

+4.2% diameter, 0.0" width

335/45R21 is 32.87" tall vs 31.55". More than the 3% rule of thumb, so check carefully before switching.

31.6"21" rim5.3"13.2" wide
335/40R21 (solid) compared with 335/45R21 (dashed outline), drawn to scale

With 335/45R21 tires, when your speedometer says 60 mph you are really going

62.5 mph

335/45R21 is +1.32 inches (+4.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

335/40R21335/45R21Difference%
Overall diameter31.55"32.87"+1.32"+4.2%
Section width13.19"13.19"0.00"0.0%
Sidewall height5.28"5.94"+0.66"+12.5%
Circumference99.12"103.26"+4.14"+4.2%
Revolutions per mile639.2613.6−25.6−4.0%

Speedometer difference

If your vehicle came with 335/40R21 and you fit 335/45R21, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.8 mph+0.8 mph
30 mph31.3 mph+1.3 mph
40 mph41.7 mph+1.7 mph
50 mph52.1 mph+2.1 mph
60 mph62.5 mph+2.5 mph
65 mph67.7 mph+2.7 mph
70 mph72.9 mph+2.9 mph
75 mph78.1 mph+3.1 mph
80 mph83.3 mph+3.3 mph

Each size on its own

Questions

Which is bigger, 335/40R21 or 335/45R21?
335/45R21 is taller by 1.32 inches (32.87" vs 31.55"). 335/40R21 is the same width.
Can I replace 335/40R21 with 335/45R21?
It is not recommended without checking carefully. The diameter difference is +4.2%, 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 335/45R21 change my speedometer?
When your speedometer reads 60 mph with 335/45R21 fitted (calibrated for 335/40R21), your real speed is 62.5 mph. Your odometer will under-count miles by about 4.2%.
Will 335/45R21 lift my vehicle?
Ride height changes by half the diameter difference: +0.66 inches of ground clearance at the axle.

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