Tire Size Box

295/35R17 vs 285/40R17

285/40R17 compared with 295/35R17

+3.4% diameter, −0.4" width

285/40R17 is 25.98" tall vs 25.13". More than the 3% rule of thumb, so check carefully before switching.

25.1"17" rim4.1"11.6" wide
295/35R17 (solid) compared with 285/40R17 (dashed outline), drawn to scale

With 285/40R17 tires, when your speedometer says 60 mph you are really going

62.0 mph

285/40R17 is +0.85 inches (+3.4%) in overall diameter. That is more than the 3% most shops and makers recommend.

295/35R17285/40R17Difference%
Overall diameter25.13"25.98"+0.85"+3.4%
Section width11.61"11.22"−0.39"−3.4%
Sidewall height4.06"4.49"+0.42"+10.4%
Circumference78.95"81.61"+2.66"+3.4%
Revolutions per mile802.6776.4−26.2−3.3%

Speedometer difference

If your vehicle came with 295/35R17 and you fit 285/40R17, 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 mph51.7 mph+1.7 mph
60 mph62.0 mph+2.0 mph
65 mph67.2 mph+2.2 mph
70 mph72.4 mph+2.4 mph
75 mph77.5 mph+2.5 mph
80 mph82.7 mph+2.7 mph

Each size on its own

Questions

Which is bigger, 295/35R17 or 285/40R17?
285/40R17 is taller by 0.85 inches (25.98" vs 25.13"). 295/35R17 is wider by 0.39 inches.
Can I replace 295/35R17 with 285/40R17?
It is not recommended without checking carefully. The diameter difference is +3.4%, 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 285/40R17 change my speedometer?
When your speedometer reads 60 mph with 285/40R17 fitted (calibrated for 295/35R17), your real speed is 62.0 mph. Your odometer will under-count miles by about 3.4%.
Will 285/40R17 lift my vehicle?
Ride height changes by half the diameter difference: +0.42 inches of ground clearance at the axle.

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