Tire Size Box

205/40R17 vs 205/50R17

205/50R17 compared with 205/40R17

+6.9% diameter, 0.0" width

205/50R17 is 25.07" tall vs 23.46". More than the 3% rule of thumb, so check carefully before switching.

23.5"17" rim3.2"8.1" wide
205/40R17 (solid) compared with 205/50R17 (dashed outline), drawn to scale

With 205/50R17 tires, when your speedometer says 60 mph you are really going

64.1 mph

205/50R17 is +1.61 inches (+6.9%) in overall diameter. That is more than the 3% most shops and makers recommend.

205/40R17205/50R17Difference%
Overall diameter23.46"25.07"+1.61"+6.9%
Section width8.07"8.07"0.00"0.0%
Sidewall height3.23"4.04"+0.81"+25.0%
Circumference73.69"78.76"+5.07"+6.9%
Revolutions per mile859.8804.4−55.4−6.4%

Speedometer difference

If your vehicle came with 205/40R17 and you fit 205/50R17, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.4 mph+1.4 mph
30 mph32.1 mph+2.1 mph
40 mph42.8 mph+2.8 mph
50 mph53.4 mph+3.4 mph
60 mph64.1 mph+4.1 mph
65 mph69.5 mph+4.5 mph
70 mph74.8 mph+4.8 mph
75 mph80.2 mph+5.2 mph
80 mph85.5 mph+5.5 mph

Each size on its own

Questions

Which is bigger, 205/40R17 or 205/50R17?
205/50R17 is taller by 1.61 inches (25.07" vs 23.46"). 205/40R17 is the same width.
Can I replace 205/40R17 with 205/50R17?
It is not recommended without checking carefully. The diameter difference is +6.9%, 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 205/50R17 change my speedometer?
When your speedometer reads 60 mph with 205/50R17 fitted (calibrated for 205/40R17), your real speed is 64.1 mph. Your odometer will under-count miles by about 6.9%.
Will 205/50R17 lift my vehicle?
Ride height changes by half the diameter difference: +0.81 inches of ground clearance at the axle.

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