Tire Size Box

335/35R20 vs 335/40R20

335/40R20 compared with 335/35R20

+4.5% diameter, 0.0" width

335/40R20 is 30.55" tall vs 29.23". More than the 3% rule of thumb, so check carefully before switching.

29.2"20" rim4.6"13.2" wide
335/35R20 (solid) compared with 335/40R20 (dashed outline), drawn to scale

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

62.7 mph

335/40R20 is +1.32 inches (+4.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

335/35R20335/40R20Difference%
Overall diameter29.23"30.55"+1.32"+4.5%
Section width13.19"13.19"0.00"0.0%
Sidewall height4.62"5.28"+0.66"+14.3%
Circumference91.84"95.98"+4.14"+4.5%
Revolutions per mile689.9660.1−29.8−4.3%

Speedometer difference

If your vehicle came with 335/35R20 and you fit 335/40R20, 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 mph62.7 mph+2.7 mph
65 mph67.9 mph+2.9 mph
70 mph73.2 mph+3.2 mph
75 mph78.4 mph+3.4 mph
80 mph83.6 mph+3.6 mph

Each size on its own

Questions

Which is bigger, 335/35R20 or 335/40R20?
335/40R20 is taller by 1.32 inches (30.55" vs 29.23"). 335/35R20 is the same width.
Can I replace 335/35R20 with 335/40R20?
It is not recommended without checking carefully. The diameter difference is +4.5%, 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 335/35R20), your real speed is 62.7 mph. Your odometer will under-count miles by about 4.5%.
Will 335/40R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.66 inches of ground clearance at the axle.

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