245/40R20
Overall diameter 704 mm
245/40R20 — 704 mm tall, and what it swaps with
245/40R20 is 245 mm wide with a 40% sidewall on a 20-inch wheel. That sidewall is 98 mm, so the tyre stands 704 mm tall and turns 452.1 times per kilometre.
- Section width
- 245 mm
- Aspect ratio
- 40 %
- Wheel size
- 20 in (508 mm)
- Sidewall height
- 98 mm
- Overall diameter
- 704 mm (27.72 in)
- Circumference
- 2211.7 mm
- Turns per km
- 452.1
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.
285/30R21704.4 mm · +0.06% you go faster225/55R18704.7 mm · +0.1% you go faster245/35R21704.9 mm · +0.13% you go faster245/45R19703.1 mm · -0.13% you go slower275/40R19702.6 mm · -0.2% you go slower245/50R18702.2 mm · -0.26% you go slower225/60R17701.8 mm · -0.31% you go slower285/25R22701.3 mm · -0.38% you go slower215/70R16707.4 mm · +0.48% you go faster285/35R20707.5 mm · +0.5% you go faster275/35R20700.5 mm · -0.5% you go slower225/65R16698.9 mm · -0.72% you go slower
Same profile, different width
Other sizes for this wheel
20-inch wheels
235/35R20 672.5mm235/45R20 719.5mm235/55R20 766.5mm245/30R20 655mm245/35R20 679.5mm245/40R20 704mm245/45R20 728.5mm245/50R20 753mm255/30R20 661mm255/35R20 686.5mm255/40R20 712mm255/45R20 737.5mm255/50R20 763mm265/30R20 667mm265/35R20 693.5mm265/40R20 720mm265/45R20 746.5mm265/50R20 773mm275/30R20 673mm275/35R20 700.5mm275/40R20 728mm275/45R20 755.5mm275/55R20 810.5mm285/30R20 679mm285/35R20 707.5mm285/40R20 736mm285/50R20 793mm295/30R20 685mm295/35R20 714.5mm305/30R20 691mm315/35R20 728.5mm
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 245/40R20?
704 mm — the 508 mm wheel plus the 98 mm sidewall at top and bottom.
Q. How many turns per kilometre does 245/40R20 make?
Its circumference is 2211.7 mm, so 452.1 turns.
Q. What can I swap it for?
12 sizes stay within 3% of its diameter — the closest is 285/30R21 at 704.4 mm.
Q. Why is the sidewall 98 mm?
Because it is 40% of the 245 mm width. The aspect ratio is a proportion of the width, not a length.