Tire Size Box

285/35R17 vs 275/40R17

275/40R17 compared with 285/35R17

+3.2% diameter, −0.4" width

275/40R17 is 25.66" tall vs 24.85". More than the 3% rule of thumb, so check carefully before switching.

24.9"17" rim3.9"11.2" wide
285/35R17 (solid) compared with 275/40R17 (dashed outline), drawn to scale

With 275/40R17 tires, when your speedometer says 60 mph you are really going

61.9 mph

275/40R17 is +0.81 inches (+3.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

285/35R17275/40R17Difference%
Overall diameter24.85"25.66"+0.81"+3.2%
Section width11.22"10.83"−0.39"−3.5%
Sidewall height3.93"4.33"+0.40"+10.3%
Circumference78.08"80.62"+2.54"+3.2%
Revolutions per mile811.5785.9−25.5−3.1%

Speedometer difference

If your vehicle came with 285/35R17 and you fit 275/40R17, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.6 mph+0.6 mph
30 mph31.0 mph+1.0 mph
40 mph41.3 mph+1.3 mph
50 mph51.6 mph+1.6 mph
60 mph61.9 mph+1.9 mph
65 mph67.1 mph+2.1 mph
70 mph72.3 mph+2.3 mph
75 mph77.4 mph+2.4 mph
80 mph82.6 mph+2.6 mph

Each size on its own

Questions

Which is bigger, 285/35R17 or 275/40R17?
275/40R17 is taller by 0.81 inches (25.66" vs 24.85"). 285/35R17 is wider by 0.39 inches.
Can I replace 285/35R17 with 275/40R17?
It is not recommended without checking carefully. The diameter difference is +3.2%, 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 275/40R17 change my speedometer?
When your speedometer reads 60 mph with 275/40R17 fitted (calibrated for 285/35R17), your real speed is 61.9 mph. Your odometer will under-count miles by about 3.2%.
Will 275/40R17 lift my vehicle?
Ride height changes by half the diameter difference: +0.40 inches of ground clearance at the axle.

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