255/35R21
Overall diameter 711.9 mm
255/35R21 — 711.9 mm tall, and what it swaps with
255/35R21 is 255 mm wide with a 35% sidewall on a 21-inch wheel. That sidewall is 89.25 mm, so the tyre stands 711.9 mm tall and turns 447.1 times per kilometre.
- Section width
- 255 mm
- Aspect ratio
- 35 %
- Wheel size
- 21 in (533.4 mm)
- Sidewall height
- 89.25 mm
- Overall diameter
- 711.9 mm (28.03 in)
- Circumference
- 2236.5 mm
- Turns per km
- 447.1
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.
255/40R20712 mm · +0.01% you go faster255/30R22711.8 mm · -0.01% you go slower255/45R19712.1 mm · +0.03% you go faster215/65R17711.3 mm · -0.08% you go slower285/40R19710.6 mm · -0.18% you go slower235/60R17713.8 mm · +0.27% you go faster295/35R20714.5 mm · +0.37% you go faster235/55R18715.7 mm · +0.53% you go faster315/25R22716.3 mm · +0.62% you go faster285/35R20707.5 mm · -0.62% you go slower305/30R21716.4 mm · +0.63% you go faster215/70R16707.4 mm · -0.63% you go slower
Same profile, different width
Other sizes for this wheel
21-inch wheels
245/35R21 704.9mm245/40R21 729.4mm245/45R21 753.9mm255/35R21 711.9mm255/40R21 737.4mm265/35R21 718.9mm265/40R21 745.4mm265/45R21 771.9mm275/30R21 698.4mm275/35R21 725.9mm275/40R21 753.4mm275/45R21 780.9mm285/30R21 704.4mm285/35R21 732.9mm285/40R21 761.4mm295/35R21 739.9mm305/30R21 716.4mm315/30R21 722.4mm
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.
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 is the overall diameter of 255/35R21?
711.9 mm — the 533.4 mm wheel plus the 89.25 mm sidewall at top and bottom.
Q. How many turns per kilometre does 255/35R21 make?
Its circumference is 2236.5 mm, so 447.1 turns.
Q. What can I swap it for?
12 sizes stay within 3% of its diameter — the closest is 255/40R20 at 712 mm.
Q. Why is the sidewall 89.25 mm?
Because it is 35% of the 255 mm width. The aspect ratio is a proportion of the width, not a length.