Tire Size Box

185/50R15 vs 205/50R15

205/50R15 compared with 185/50R15

+3.5% diameter, +0.8" width

205/50R15 is 23.07" tall vs 22.28". More than the 3% rule of thumb, so check carefully before switching.

22.3"15" rim3.6"7.3" wide
185/50R15 (solid) compared with 205/50R15 (dashed outline), drawn to scale

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

62.1 mph

205/50R15 is +0.79 inches (+3.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

185/50R15205/50R15Difference%
Overall diameter22.28"23.07"+0.79"+3.5%
Section width7.28"8.07"+0.79"+10.8%
Sidewall height3.64"4.04"+0.39"+10.8%
Circumference70.01"72.48"+2.47"+3.5%
Revolutions per mile905.1874.2−30.9−3.4%

Speedometer difference

If your vehicle came with 185/50R15 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 mph41.4 mph+1.4 mph
50 mph51.8 mph+1.8 mph
60 mph62.1 mph+2.1 mph
65 mph67.3 mph+2.3 mph
70 mph72.5 mph+2.5 mph
75 mph77.7 mph+2.7 mph
80 mph82.8 mph+2.8 mph

Each size on its own

Questions

Which is bigger, 185/50R15 or 205/50R15?
205/50R15 is taller by 0.79 inches (23.07" vs 22.28"). 205/50R15 is wider by 0.79 inches.
Can I replace 185/50R15 with 205/50R15?
It is not recommended without checking carefully. The diameter difference is +3.5%, 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 185/50R15), your real speed is 62.1 mph. Your odometer will under-count miles by about 3.5%.
Will 205/50R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.39 inches of ground clearance at the axle.

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