Tire Size Box

345/35R20 vs 335/40R20

335/40R20 compared with 345/35R20

+3.5% diameter, −0.4" width

335/40R20 is 30.55" tall vs 29.51". More than the 3% rule of thumb, so check carefully before switching.

29.5"20" rim4.8"13.6" wide
345/35R20 (solid) compared with 335/40R20 (dashed outline), drawn to scale

With 335/40R20 tires, when your speedometer says 60 mph you are really going

62.1 mph

335/40R20 is +1.04 inches (+3.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

345/35R20335/40R20Difference%
Overall diameter29.51"30.55"+1.04"+3.5%
Section width13.58"13.19"−0.39"−2.9%
Sidewall height4.75"5.28"+0.52"+11.0%
Circumference92.70"95.98"+3.28"+3.5%
Revolutions per mile683.5660.1−23.3−3.4%

Speedometer difference

If your vehicle came with 345/35R20 and you fit 335/40R20, 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, 345/35R20 or 335/40R20?
335/40R20 is taller by 1.04 inches (30.55" vs 29.51"). 345/35R20 is wider by 0.39 inches.
Can I replace 345/35R20 with 335/40R20?
It is not recommended without checking carefully. The diameter difference is +3.5%, 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 335/40R20 change my speedometer?
When your speedometer reads 60 mph with 335/40R20 fitted (calibrated for 345/35R20), your real speed is 62.1 mph. Your odometer will under-count miles by about 3.5%.
Will 335/40R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.52 inches of ground clearance at the axle.

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