204 tyre sizes — diameters and what you can swap to
205/55R16 means 205 mm wide, a 55 % sidewall and a 16-inch wheel. From those three numbers come the sidewall height, the overall diameter, the turns per kilometre and every size you can swap to.
How the code reads
The 205 is millimetres, the 55 is a percentage of that width, and only the 16 is inches. The R stands for radial construction.
- Section width
- 205 mm
- Aspect ratio
- 55 %
- Wheel size
- 16 in
Sizes you can swap to
Only sizes whose overall diameter stays within 3% are listed. A different diameter covers a different distance per turn, and that gap becomes speedometer error.
The largest and the smallest
A bigger wheel does not mean a much bigger tyre. As the wheel grows, the sidewall thins out by roughly the same amount.
Browse by wheel size
Most people keep the wheel and change only the tyre. Start from the wheel size you already have.
13-inch wheels
14-inch wheels
15-inch wheels
16-inch wheels
17-inch wheels
18-inch wheels
19-inch wheels
20-inch wheels
21-inch wheels
22-inch wheels
How to read this
- The first three digits are the width in mm, the middle two are the aspect ratio in percent, the last two the wheel in inches.
- Sidewall height = width × aspect ÷ 100. For 205/55 that is 112.75 mm.
- Overall diameter = wheel diameter + twice the sidewall. A 16-inch wheel is 406.4 mm.
- Once the diameter shifts by more than 3%, the speedometer and odometer drift by the same amount.
Frequently asked questions
Q. What changes with a lower aspect ratio?
A thinner sidewall sharpens the steering but passes road shock straight through, and the wheel itself is easier to kerb.
Q. Can I fit one size wider?
Usually yes, if the rim is wide enough and the overall diameter stays within 3%. Going wider normally means dropping the aspect ratio to keep the diameter.
Q. Why does a different diameter upset the speedometer?
The speedometer counts wheel rotations. A taller tyre covers more ground per turn while the dial keeps counting the same, so you are actually going faster than it reads.
Q. Can front and rear sizes differ?
Many cars leave the factory with wider rears. On four-wheel drive, though, mismatched diameters strain the drivetrain.
Q. What does the R stand for?
Radial construction. Virtually every modern passenger tyre is radial, which is why the letter is almost always R.