285/35R21
Overall diameter 732.9 mm
285/35R21 — 732.9 mm tall, and what it swaps with
285/35R21 is 285 mm wide with a 35% sidewall on a 21-inch wheel. That sidewall is 99.75 mm, so the tyre stands 732.9 mm tall and turns 434.3 times per kilometre.
- Section width
- 285 mm
- Aspect ratio
- 35 %
- Wheel size
- 21 in (533.4 mm)
- Sidewall height
- 99.75 mm
- Overall diameter
- 732.9 mm (28.85 in)
- Circumference
- 2302.5 mm
- Turns per km
- 434.3
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.
235/75R15733.5 mm · +0.08% you go faster235/70R16735.4 mm · +0.34% you go faster225/55R19730.1 mm · -0.38% you go slower275/45R19730.1 mm · -0.38% you go slower295/30R22735.8 mm · +0.4% you go faster285/40R20736 mm · +0.42% you go faster245/40R21729.4 mm · -0.48% you go slower235/65R17737.3 mm · +0.6% you go faster255/35R22737.3 mm · +0.6% you go faster245/45R20728.5 mm · -0.6% you go slower315/35R20728.5 mm · -0.6% you go slower255/40R21737.4 mm · +0.61% you go faster
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 285/35R21?
732.9 mm — the 533.4 mm wheel plus the 99.75 mm sidewall at top and bottom.
Q. How many turns per kilometre does 285/35R21 make?
Its circumference is 2302.5 mm, so 434.3 turns.
Q. What can I swap it for?
12 sizes stay within 3% of its diameter — the closest is 235/75R15 at 733.5 mm.
Q. Why is the sidewall 99.75 mm?
Because it is 35% of the 285 mm width. The aspect ratio is a proportion of the width, not a length.