Tire Size Box

265/35R20 vs 265/40R20

265/40R20 compared with 265/35R20

+3.8% diameter, 0.0" width

265/40R20 is 28.35" tall vs 27.30". More than the 3% rule of thumb, so check carefully before switching.

27.3"20" rim3.7"10.4" wide
265/35R20 (solid) compared with 265/40R20 (dashed outline), drawn to scale

With 265/40R20 tires, when your speedometer says 60 mph you are really going

62.3 mph

265/40R20 is +1.04 inches (+3.8%) in overall diameter. That is more than the 3% most shops and makers recommend.

265/35R20265/40R20Difference%
Overall diameter27.30"28.35"+1.04"+3.8%
Section width10.43"10.43"0.00"0.0%
Sidewall height3.65"4.17"+0.52"+14.3%
Circumference85.78"89.05"+3.28"+3.8%
Revolutions per mile738.7711.5−27.2−3.7%

Speedometer difference

If your vehicle came with 265/35R20 and you fit 265/40R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.8 mph+0.8 mph
30 mph31.1 mph+1.1 mph
40 mph41.5 mph+1.5 mph
50 mph51.9 mph+1.9 mph
60 mph62.3 mph+2.3 mph
65 mph67.5 mph+2.5 mph
70 mph72.7 mph+2.7 mph
75 mph77.9 mph+2.9 mph
80 mph83.1 mph+3.1 mph

Each size on its own

Questions

Which is bigger, 265/35R20 or 265/40R20?
265/40R20 is taller by 1.04 inches (28.35" vs 27.30"). 265/35R20 is the same width.
Can I replace 265/35R20 with 265/40R20?
It is not recommended without checking carefully. The diameter difference is +3.8%, 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 265/40R20 change my speedometer?
When your speedometer reads 60 mph with 265/40R20 fitted (calibrated for 265/35R20), your real speed is 62.3 mph. Your odometer will under-count miles by about 3.8%.
Will 265/40R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.52 inches of ground clearance at the axle.

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