Tire Size Box

345/40R20 vs 335/45R20

335/45R20 compared with 345/40R20

+3.3% diameter, −0.4" width

335/45R20 is 31.87" tall vs 30.87". More than the 3% rule of thumb, so check carefully before switching.

30.9"20" rim5.4"13.6" wide
345/40R20 (solid) compared with 335/45R20 (dashed outline), drawn to scale

With 335/45R20 tires, when your speedometer says 60 mph you are really going

62.0 mph

335/45R20 is +1.00 inches (+3.3%) in overall diameter. That is more than the 3% most shops and makers recommend.

345/40R20335/45R20Difference%
Overall diameter30.87"31.87"+1.00"+3.3%
Section width13.58"13.19"−0.39"−2.9%
Sidewall height5.43"5.94"+0.50"+9.2%
Circumference96.97"100.12"+3.15"+3.3%
Revolutions per mile653.4632.8−20.6−3.2%

Speedometer difference

If your vehicle came with 345/40R20 and you fit 335/45R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.0 mph+1.0 mph
40 mph41.3 mph+1.3 mph
50 mph51.6 mph+1.6 mph
60 mph62.0 mph+2.0 mph
65 mph67.1 mph+2.1 mph
70 mph72.3 mph+2.3 mph
75 mph77.4 mph+2.4 mph
80 mph82.6 mph+2.6 mph

Each size on its own

Questions

Which is bigger, 345/40R20 or 335/45R20?
335/45R20 is taller by 1.00 inches (31.87" vs 30.87"). 345/40R20 is wider by 0.39 inches.
Can I replace 345/40R20 with 335/45R20?
It is not recommended without checking carefully. The diameter difference is +3.3%, 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 335/45R20 change my speedometer?
When your speedometer reads 60 mph with 335/45R20 fitted (calibrated for 345/40R20), your real speed is 62.0 mph. Your odometer will under-count miles by about 3.3%.
Will 335/45R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.50 inches of ground clearance at the axle.

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