Decode Goodyear aircraft tire sizes and sidewall information
How to read Goodyear aircraft tire sizes in Three Part, Radial, Metric, Type VII and Type III formats, and how to separate size from other sidewall markings.
Contents
A Goodyear aircraft tire size is a short code made of nominal dimensions. Depending on the format, it gives some combination of three numbers: overall diameter, section width and rim diameter. Section width is the tire's width across its widest point, and rim diameter is the size of the wheel it mounts on. For example, H49x19.0-22 means a 49-inch diameter, a 19.0-inch section width and a 22-inch rim. The format determines which numbers appear and what units they use, so identify the format before you read the numbers. Everything else on the sidewall, such as part numbers, serial numbers, ratings and retread data, is separate from the size and should be read as separate information.
The five size formats at a glance
Goodyear's aviation tire care guide (2024 edition) describes these formats. All the dimensions are nominal, meaning they are design reference values rather than measurements of a particular tire.
| Format | Example | What each number means | Units |
| Three Part | H49x19.0-22 | Diameter x section width - rim diameter | Inches |
| Radial | 32x8.8R16 | Diameter x section width R rim diameter | Inches |
| Metric | 670x210-12 | Diameter x section width - rim diameter | Millimeters for diameter and width, inches for rim |
| Type VII | 49x17 | Diameter x section width (no rim figure) | Inches |
| Type III | 8.50-10 | Section width - rim diameter (no diameter figure) | Inches |
Three Part sizes and the H or B prefix
A Three Part size gives all three dimensions. The "x" separates diameter from section width, and the dash comes before the rim diameter. In H49x19.0-22, the tire is nominally 49 inches tall, 19.0 inches wide and fits a 22-inch rim.
Some Three Part sizes begin with a letter. According to Goodyear, a leading H or B means the tire mounts on a wheel whose rim width is about 65% of the tire's section width. A B also means the bead has a 15-degree taper instead of a 5-degree taper. The bead is the edge of the tire that seats against the wheel. Because the prefix carries real information about the wheel and bead, keep it whenever you write down or compare a size.
Illustrative calculation: for H49x19.0-22, 65% of the 19.0-inch section width is about 12.4 inches, so the rim width is roughly 12.4 inches. This figure is approximate arithmetic based on Goodyear's stated ratio. It is not a published wheel specification.
Radial sizes
Radial sizes follow the Three Part order, but an R replaces the dash. In 32x8.8R16, the tire is nominally 32 inches in diameter, 8.8 inches in section width and fits a 16-inch rim. The R marks radial construction, so 32x8.8R16 and a hypothetical 32x8.8-16 are different designations even though the numbers match.
Metric, Type VII and Type III sizes
- Metric (670x210-12): The first two numbers are in millimeters, giving a 670 mm diameter and a 210 mm section width. The rim figure is in inches, here 12. Converted, 670 mm is about 26.4 inches and 210 mm is about 8.3 inches. Do not convert the rim number, because it is already in inches.
- Type VII (49x17): This format gives only diameter and section width, here 49 inches and 17 inches. Rim diameter is not part of the designation.
- Type III (8.50-10): This format gives section width and rim diameter, here 8.50 inches and 10 inches. Overall diameter is not part of the designation.
The two-number formats are easy to confuse. 49x17 uses an "x" and starts with diameter. 8.50-10 uses a dash and starts with width. Check the separator and the format before you assign any meaning to a number.
Sidewall markings that are not the size
Goodyear's marking diagrams treat the tire name and size as one item among several separate pieces of information. Record each of the following on its own instead of mixing it into the size:
- Part number and serial number: These identify the specific product and the individual tire.
- Plant identification: This shows where the tire was made.
- Tubeless or tube-type marking: This states whether the tire needs an inner tube.
- Ply rating, load rating and speed rating: These give performance limits. They are not dimensions.
- Specification references: These cite the standards the tire was built to.
- AEA construction codes: These are construction identifiers, separate from the size code.
Retread markings on the shoulder
Retreaded tires carry extra information on the shoulder, which is the area where the tread meets the sidewall. These markings include the retread level, the retread date and the plant and country where the retread was done. They describe the tire's service history. They do not change the size designation, so record them in their own field.
A transcription worksheet for reading a tire
A simple worksheet helps keep the size separate from everything else on the sidewall. Copy the full designation exactly, including prefixes, the "x", dashes and the R. Then break it into tokens. The example below is illustrative and uses the Three Part size from Goodyear's guide.
| Token | Goodyear format | Defined meaning | Unit | Nominal value | Document edition/page |
| H | Three Part prefix | Rim width about 65% of section width; 5-degree bead taper | n/a | n/a | Record the edition and page you used |
| 49 | Three Part | Overall diameter | in | 49 | Same |
| 19.0 | Three Part | Section width | in | 19.0 | Same |
| 22 | Three Part | Rim diameter | in | 22 | Same |
Give branding, part number, serial number, ratings, specification references, construction codes and retread identifiers their own fields below the size table. If a designation does not match any documented format, mark it as undecoded. Do not guess at the meaning of the numbers. Recheck the full marking against the manufacturer's documentation until it matches.
What the size code does not tell you
Decoding a size tells you the tire's nominal dimensions and type. It does not tell you whether the tire is approved for a particular aircraft. Two tires with the same size can differ in ply rating, load rating, speed rating or construction. Installation eligibility comes from the aircraft's approved documentation and the tire manufacturer's current data, not from the sidewall code alone. When you compare tires, match the complete designation, including the prefix and the R, and then check that the separately listed ratings meet the aircraft's requirements.
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