Tire Size Box

285/40R17 vs 285/50R17

285/50R17 compared with 285/40R17

+8.6% diameter, 0.0" width

285/50R17 is 28.22" tall vs 25.98". More than the 3% rule of thumb, so check carefully before switching.

26.0"17" rim4.5"11.2" wide
285/40R17 (solid) compared with 285/50R17 (dashed outline), drawn to scale

With 285/50R17 tires, when your speedometer says 60 mph you are really going

65.2 mph

285/50R17 is +2.24 inches (+8.6%) in overall diameter. That is more than the 3% most shops and makers recommend.

285/40R17285/50R17Difference%
Overall diameter25.98"28.22"+2.24"+8.6%
Section width11.22"11.22"0.00"0.0%
Sidewall height4.49"5.61"+1.12"+25.0%
Circumference81.61"88.66"+7.05"+8.6%
Revolutions per mile776.4714.7−61.7−8.0%

Speedometer difference

If your vehicle came with 285/40R17 and you fit 285/50R17, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.7 mph+1.7 mph
30 mph32.6 mph+2.6 mph
40 mph43.5 mph+3.5 mph
50 mph54.3 mph+4.3 mph
60 mph65.2 mph+5.2 mph
65 mph70.6 mph+5.6 mph
70 mph76.0 mph+6.0 mph
75 mph81.5 mph+6.5 mph
80 mph86.9 mph+6.9 mph

Each size on its own

Questions

Which is bigger, 285/40R17 or 285/50R17?
285/50R17 is taller by 2.24 inches (28.22" vs 25.98"). 285/40R17 is the same width.
Can I replace 285/40R17 with 285/50R17?
It is not recommended without checking carefully. The diameter difference is +8.6%, 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 285/50R17 change my speedometer?
When your speedometer reads 60 mph with 285/50R17 fitted (calibrated for 285/40R17), your real speed is 65.2 mph. Your odometer will under-count miles by about 8.6%.
Will 285/50R17 lift my vehicle?
Ride height changes by half the diameter difference: +1.12 inches of ground clearance at the axle.

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