Tire Size Box

205/45R15 vs 205/50R15

205/50R15 compared with 205/45R15

+3.6% diameter, 0.0" width

205/50R15 is 23.07" tall vs 22.26". More than the 3% rule of thumb, so check carefully before switching.

22.3"15" rim3.6"8.1" wide
205/45R15 (solid) compared with 205/50R15 (dashed outline), drawn to scale

With 205/50R15 tires, when your speedometer says 60 mph you are really going

62.2 mph

205/50R15 is +0.81 inches (+3.6%) in overall diameter. That is more than the 3% most shops and makers recommend.

205/45R15205/50R15Difference%
Overall diameter22.26"23.07"+0.81"+3.6%
Section width8.07"8.07"0.00"0.0%
Sidewall height3.63"4.04"+0.40"+11.1%
Circumference69.94"72.48"+2.54"+3.6%
Revolutions per mile905.9874.2−31.7−3.5%

Speedometer difference

If your vehicle came with 205/45R15 and you fit 205/50R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.1 mph+1.1 mph
40 mph41.5 mph+1.5 mph
50 mph51.8 mph+1.8 mph
60 mph62.2 mph+2.2 mph
65 mph67.4 mph+2.4 mph
70 mph72.5 mph+2.5 mph
75 mph77.7 mph+2.7 mph
80 mph82.9 mph+2.9 mph

Each size on its own

Questions

Which is bigger, 205/45R15 or 205/50R15?
205/50R15 is taller by 0.81 inches (23.07" vs 22.26"). 205/45R15 is the same width.
Can I replace 205/45R15 with 205/50R15?
It is not recommended without checking carefully. The diameter difference is +3.6%, 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 205/50R15 change my speedometer?
When your speedometer reads 60 mph with 205/50R15 fitted (calibrated for 205/45R15), your real speed is 62.2 mph. Your odometer will under-count miles by about 3.6%.
Will 205/50R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.40 inches of ground clearance at the axle.

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