Read three-number radial ATV and UTV tire sizes and separate wheel specifications
How to decode radial ATV and UTV tire sizes like 27 x 11 R14: diameter, width, the R symbol and rim diameter, plus how nominal sizes differ from catalog dimensions and rim-size entries.
Contents
The short answer
A radial ATV or UTV tire size written in the three-number format reads as diameter, width, construction and rim diameter, all in inches. Polaris uses 27 x 11 R14 as its example: 27 is the tire's diameter, 11 is the tire's width, R means radial construction, and 14 is the diameter of the rim the tire mounts on.
Two conditions change how you should use those numbers. First, the figures in the designation are nominal labels, not exact measurements; tire makers publish the actual overall diameter and width in separate catalog columns. Second, the tire size gives only one wheel dimension, the rim diameter. The full wheel specification is listed separately and carries information the tire size does not.
Each part of the designation
| Element | Example value (27 x 11 R14) | What it means |
| First number | 27 | Nominal tire diameter, in inches |
| Second number | 11 | Nominal tire width, in inches |
| Letter R | R | Radial construction |
| Last number | 14 | Rim diameter, in inches |
| Prefix, when present (for example AT) | AT | Identifies the tire for ATV service; it is a category marker, not a dimension |
Some catalogs print the size without spaces, such as AT25X8R12. Read it the same way: AT marks ATV service, 25 is the nominal diameter, 8 is the nominal width, R marks radial construction, and 12 is the rim diameter. Keep the prefix and the R separate from the numbers in your notes so a category code is never mistaken for a measurement.
Nominal size versus tabulated dimensions
The 2025 Maxxis powersports catalog shows why the size on the sidewall should not be treated as a measurement. Its tables list Tire Size, Overall Diameter, Overall Width and Rim Size as separate columns. For the Bighorn radial front tire in size AT25X8R12, the catalog gives an overall diameter of 25.4 inches, an overall width of 8.0 inches and a rim size of 12X6.5. The Maxxis Bighorn product page lists the same size under part number TM00296600 with the same 25.4-inch diameter, 8.0-inch section width and 12X6.5 rim size.
Illustrative comparison: the designation says 25, and the catalog says 25.4. Subtracting gives 25.4 − 25 = 0.4 inch. That 0.4 inch is a difference between two published catalog values, not a measurement of a mounted tire and not a statement about whether the tire suits a particular vehicle. In this example the width matches its nominal value (8 and 8.0), but you should check every size you compare rather than assume either dimension will match.
Why the wheel specification is separate
In the Bighorn example, the rim size entry is 12X6.5. The 12 matches the rim diameter at the end of the tire size. The 6.5 is a wheel dimension that appears nowhere in AT25X8R12. That is the key distinction: the 8 in the tire designation describes the tire, not the wheel, so you cannot read a wheel width out of a three-number tire size. Look for the maker's rim-size entry for the specific tire and size.
How to decode and compare a size
- 1. Copy the full designation exactly as printed, including any prefix such as AT and the R.
- 2. Split it into nominal diameter, nominal width, construction symbol and rim diameter.
- 3. Find the tire maker's catalog or product page for that exact model and size, and note the part number and catalog edition.
- 4. Record the tabulated overall diameter, overall width and rim-size entry in their own columns, separate from the nominal figures.
- 5. Calculate any difference by subtracting the nominal value from the tabulated value, and label the result as a catalog comparison.
- 6. Compare only rows that share the same part number and source; do not blend figures from different catalog editions or webpages for the same size.
A worksheet you can reuse
| Field | Bighorn front example |
| Full designation | AT25X8R12 |
| Service prefix | AT (ATV) |
| Nominal diameter (in) | 25 |
| Nominal tire width (in) | 8 |
| Construction symbol | R (radial) |
| Rim diameter (in) | 12 |
| Tabulated overall diameter (in) | 25.4 |
| Tabulated overall width (in) | 8.0 |
| Rim-size entry | 12X6.5 |
| Part number | TM00296600 |
| Source edition | 2025 Maxxis US powersports catalog |
| Diameter difference (tabulated − nominal) | 0.4 in, catalog comparison only |
Sizes written with a hyphen, and vehicle-specific sizes
The decoding above applies to radial sizes that carry an R. Many common ATV sizes, such as 22X9-8, are written with a hyphen instead; check the tire maker's documentation for what that format signals for the specific tire before treating it as interchangeable with a radial size. Likewise, the notation tells you what a tire is, not whether it is right for your machine. For a Honda or any other ATV or UTV, the specified tire and wheel sizes come from that vehicle's own documentation for its model year, and fitment questions belong with the vehicle and tire makers rather than with the size code alone.
Related articles
Identify headings and units in tire load-inflation tables
How to read the headings in a tire load-inflation table: tire category, size, service description, PR/Load Range/XL, single or twin fitment, load basis and pressure units.
Identify Pirelli Seal Inside and distinguish self-sealing from run-flat terminology
How to recognize Pirelli Seal Inside in a tire designation, how the sealing layer works, and why self-sealing, run-flat and added sealant belong in separate records.
How to interpret forklift press-on and pneumatic tire size markings
Decode forklift tire sizes like 16×6×10½, 200/75-100, 7.00 R12, 180/70 R8 and 18×7-8. Learn which number is outer diameter, width or rim diameter.
Interpret legacy numeric and alphanumeric tire sizes and comparison charts
What a 7.35-14 tire size means, how to read old numeric and letter-series codes, and how to compare conversion-chart rows with real tire specifications.
Read agricultural tire size markings
What the numbers on tractor tires mean: decode modern metric and legacy inch sizes, R and dash construction symbols, and the two different slash conventions.
Reading Motorcycle Tire Size and Sidewall Markings
Decode motorcycle tire sizes such as 120/70 ZR17 M/C (58W): nominal width, aspect ratio, construction, rim diameter, load index and speed symbol, plus a printable decoding worksheet.
Tire Number Guide: Understanding Manufacturer OE Markings Like Star, MO and AO
What OE tire markings such as the BMW star, Mercedes MO, Audi AO and Porsche N0 mean, where to find them, and how to use them when choosing replacements.
Motorcycle Tires: Front and Rear Sizes, Terminology and Mixing Rules Explained
Can a motorcycle run different tire sizes front and rear? Learn how to read motorcycle tire sizes, why front and rear tires differ, and what to check before mixing sizes or types.
Do LT tires ride rough?
LT (light truck) tires generally ride firmer than P-metric tires because they are built more heavily to carry loads. Here is why, and what changes the answer.
22.5 Flotation Tires: How to Read the Size and What It Means
What 22.5 flotation tires are, how to read sizes like 550/45R22.5, how metric and inch flotation notation differ, and what to verify before choosing.