Flotation Tire Size Decoder
Decode flotation sizes such as 33x12.50R17. Calculate diameter, width, rim, sidewall height and equivalent aspect ratio in inches and mm.
Explain inch-based truck tire dimensions.
Flotation Tire Size Decoder: Tire Size Inputs
Compare two tire sizes here. Use the formulas and reference tables below for this tool's specific calculation.
How Flotation Tire Size Decoder Works?
The Flotation Tire Size Decoder works by reading the 3 inch values in a flotation code (diameter × width R rim) and deriving the sidewall and aspect ratio. The tool uses 3 steps.
Enter the code
Type a flotation size such as 35x12.50R17LT.
Read the 3 dimensions
The decoder returns a 35 in (889 mm) overall diameter, a 12.5 in (318 mm) section width and a 17 in rim.
Derive the sidewall
The decoder calculates a sidewall of (35 − 17) ÷ 2 = 9 in (229 mm) and an equivalent aspect ratio of 72%.
Flotation Tire Size Decoder Formula
The Flotation Tire Size Decoder formula is SH = (D − Rim) ÷ 2, and the equivalent aspect ratio is SH ÷ W × 100.
D x W R Rim [LT] [LI][SR]SH = (D − Rim) ÷ 2AR = SH ÷ W × 100W_mm = W × 25.4- D
- Nominal overall diameter (in)
- W
- Nominal section width (in)
- Rim
- Rim diameter (in)
Worked example
A 33x12.50R15 tire is 33 in (838 mm) tall and 12.5 in (318 mm) wide. The sidewall is (33 − 15) ÷ 2 = 9 in (229 mm). The equivalent aspect ratio is 9 ÷ 12.5 × 100 = 72%.
Flotation Tire Size Decoder Conversion Table
The Flotation Tire Size Decoder conversion table decodes 8 popular off-road and light truck flotation sizes into inches, millimeters and an equivalent aspect ratio.
| Size | Diameter | Width | Rim | Sidewall | Equivalent AR |
|---|---|---|---|---|---|
| 31x10.5R15 | 31 in (787 mm) | 10.5 in (267 mm) | 15 in | 8.00 in (203 mm) | 76% |
| 33x12.5R15 | 33 in (838 mm) | 12.5 in (318 mm) | 15 in | 9.00 in (229 mm) | 72% |
| 33x12.5R17 | 33 in (838 mm) | 12.5 in (318 mm) | 17 in | 8.00 in (203 mm) | 64% |
| 35x12.5R17 | 35 in (889 mm) | 12.5 in (318 mm) | 17 in | 9.00 in (229 mm) | 72% |
| 35x12.5R20 | 35 in (889 mm) | 12.5 in (318 mm) | 20 in | 7.50 in (190 mm) | 60% |
| 37x12.5R17 | 37 in (940 mm) | 12.5 in (318 mm) | 17 in | 10.00 in (254 mm) | 80% |
| 37x13.5R20 | 37 in (940 mm) | 13.5 in (343 mm) | 20 in | 8.50 in (216 mm) | 63% |
| 40x13.5R20 | 40 in (1016 mm) | 13.5 in (343 mm) | 20 in | 10.00 in (254 mm) | 74% |
What is Flotation Tire Size Decoder?
A Flotation Tire Size Decoder is a tool that explains inch-based truck and off-road tire sizes such as 33x12.50R17. Flotation sizing states the overall diameter directly, so a buyer reads the tire height without any math.
Flotation tires are light truck (LT) tires. Most carry load range C, D or E and need higher inflation pressure than passenger tires.
The term flotation comes from the wide footprint that keeps the tire on top of sand, mud and snow instead of sinking.
What are the uses of Flotation Tire Size Decoder?
There are 4 main uses of the Flotation Tire Size Decoder, including lift kit planning and sidewall comparison.
Lift kit planning
Match tire height to the lift and fender trim required.
Sidewall comparison
Compare sidewall height for off-road flex and rock protection.
Metric cross-reference
Get the equivalent aspect ratio for a metric search.
Wheel selection
Confirm the rim diameter and width range before buying wheels.
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