Tire Size Box

205/45R17 vs 205/50R17

205/50R17 compared with 205/45R17

+3.3% diameter, 0.0" width

205/50R17 is 25.07" tall vs 24.26". More than the 3% rule of thumb, so check carefully before switching.

24.3"17" rim3.6"8.1" wide
205/45R17 (solid) compared with 205/50R17 (dashed outline), drawn to scale

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

62.0 mph

205/50R17 is +0.81 inches (+3.3%) in overall diameter. That is more than the 3% most shops and makers recommend.

205/45R17205/50R17Difference%
Overall diameter24.26"25.07"+0.81"+3.3%
Section width8.07"8.07"0.00"0.0%
Sidewall height3.63"4.04"+0.40"+11.1%
Circumference76.23"78.76"+2.54"+3.3%
Revolutions per mile831.2804.4−26.8−3.2%

Speedometer difference

If your vehicle came with 205/45R17 and you fit 205/50R17, 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 mph72.3 mph+2.3 mph
75 mph77.5 mph+2.5 mph
80 mph82.7 mph+2.7 mph

Each size on its own

Questions

Which is bigger, 205/45R17 or 205/50R17?
205/50R17 is taller by 0.81 inches (25.07" vs 24.26"). 205/45R17 is the same width.
Can I replace 205/45R17 with 205/50R17?
It is not recommended without checking carefully. The diameter difference is +3.3%, 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 205/45R17), your real speed is 62.0 mph. Your odometer will under-count miles by about 3.3%.
Will 205/50R17 lift my vehicle?
Ride height changes by half the diameter difference: +0.40 inches of ground clearance at the axle.

Other comparisons