Tire Size Box

295/35R20 vs 285/40R20

285/40R20 compared with 295/35R20

+3.0% diameter, −0.4" width

285/40R20 is 28.98" tall vs 28.13". More than the 3% rule of thumb, so check carefully before switching.

28.1"20" rim4.1"11.6" wide
295/35R20 (solid) compared with 285/40R20 (dashed outline), drawn to scale

With 285/40R20 tires, when your speedometer says 60 mph you are really going

61.8 mph

285/40R20 is +0.85 inches (+3.0%) in overall diameter. That is more than the 3% most shops and makers recommend.

295/35R20285/40R20Difference%
Overall diameter28.13"28.98"+0.85"+3.0%
Section width11.61"11.22"−0.39"−3.4%
Sidewall height4.06"4.49"+0.42"+10.4%
Circumference88.37"91.03"+2.66"+3.0%
Revolutions per mile717.0696.0−20.9−2.9%

Speedometer difference

If your vehicle came with 295/35R20 and you fit 285/40R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.6 mph+0.6 mph
30 mph30.9 mph+0.9 mph
40 mph41.2 mph+1.2 mph
50 mph51.5 mph+1.5 mph
60 mph61.8 mph+1.8 mph
65 mph67.0 mph+2.0 mph
70 mph72.1 mph+2.1 mph
75 mph77.3 mph+2.3 mph
80 mph82.4 mph+2.4 mph

Each size on its own

Questions

Which is bigger, 295/35R20 or 285/40R20?
285/40R20 is taller by 0.85 inches (28.98" vs 28.13"). 295/35R20 is wider by 0.39 inches.
Can I replace 295/35R20 with 285/40R20?
It is not recommended without checking carefully. The diameter difference is +3.0%, 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 285/40R20 change my speedometer?
When your speedometer reads 60 mph with 285/40R20 fitted (calibrated for 295/35R20), your real speed is 61.8 mph. Your odometer will under-count miles by about 3.0%.
Will 285/40R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.42 inches of ground clearance at the axle.

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