Tire Size Box

185/45R17 vs 185/50R17

185/50R17 compared with 185/45R17

+3.1% diameter, 0.0" width

185/50R17 is 24.28" tall vs 23.56". More than the 3% rule of thumb, so check carefully before switching.

23.6"17" rim3.3"7.3" wide
185/45R17 (solid) compared with 185/50R17 (dashed outline), drawn to scale

With 185/50R17 tires, when your speedometer says 60 mph you are really going

61.9 mph

185/50R17 is +0.73 inches (+3.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

185/45R17185/50R17Difference%
Overall diameter23.56"24.28"+0.73"+3.1%
Section width7.28"7.28"0.00"0.0%
Sidewall height3.28"3.64"+0.36"+11.1%
Circumference74.00"76.29"+2.29"+3.1%
Revolutions per mile856.2830.5−25.7−3.0%

Speedometer difference

If your vehicle came with 185/45R17 and you fit 185/50R17, 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 mph61.9 mph+1.9 mph
65 mph67.0 mph+2.0 mph
70 mph72.2 mph+2.2 mph
75 mph77.3 mph+2.3 mph
80 mph82.5 mph+2.5 mph

Each size on its own

Questions

Which is bigger, 185/45R17 or 185/50R17?
185/50R17 is taller by 0.73 inches (24.28" vs 23.56"). 185/45R17 is the same width.
Can I replace 185/45R17 with 185/50R17?
It is not recommended without checking carefully. The diameter difference is +3.1%, 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 185/50R17 change my speedometer?
When your speedometer reads 60 mph with 185/50R17 fitted (calibrated for 185/45R17), your real speed is 61.9 mph. Your odometer will under-count miles by about 3.1%.
Will 185/50R17 lift my vehicle?
Ride height changes by half the diameter difference: +0.36 inches of ground clearance at the axle.

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