Shopify Automobile Tire Schema — UTQG Treadwear Grade Is a Relative Index Not a Mileage Rating, Speed Rating Letter Must Meet or Exceed Vehicle Top Speed (H=130 mph, V=149, W=168, Y=186), All-Season M+S vs All-Weather 3PMSF Snowflake (Severe Snow Certification), Load Index as Safety Spec, Tire Size 225/65R17 Decoded to Four PropertyValues

UTQG Treadwear Grade — A Relative Index, Not a Mileage Guarantee

The Uniform Tire Quality Grading (UTQG) system is mandated by NHTSA under 49 CFR Part 575.104 for passenger car tires sold in the United States. Treadwear grade is determined by driving a test tire alongside a reference Course Monitoring Tire (CMT) on a specific 400-mile Texas test loop under controlled conditions. The reference baseline grade is 100. A tire receiving a grade of 500 is expected to wear approximately 5× more slowly than the 100-grade reference tire under those exact conditions.

Real-world mileage is entirely separate from the UTQG index. Compound type is the dominant variable: ultra-high-performance (UHP) summer tires use soft compounds for maximum grip, yielding UTQG grades of 200–340 but real-world life of 15,000–30,000 miles. Grand touring all-season tires use harder compounds, yielding grades of 500–700+ with real-world life of 50,000–80,000 miles. Driving habits, inflation maintenance, alignment, road surface, and climate all affect actual tire life independently of UTQG grade.

UTQG Treadwear Grade Reference Table

Encode utqg_treadwear as an integer (e.g., 640) with a legalDisclaimer: "UTQG Treadwear grade is a relative index based on standardized government test conditions, not a mileage guarantee. Actual tire life depends on driving habits, inflation pressure, alignment, road conditions, and climate." Encode utqg_traction (A/B/C — wet braking performance on asphalt and concrete) and utqg_temperature (A/B/C — heat resistance at sustained speed) as separate string values. Grade A is the highest rating for both traction and temperature.

Speed Rating — Must Meet or Exceed Vehicle Top Speed Capability

The speed rating letter is encoded within the tire size designation. In "225/65R17H," the H at the end is the speed rating. It indicates the tire's maximum sustained speed capability based on its internal construction, heat dissipation design, and compound characteristics. Operating a tire above its rated speed generates heat beyond design parameters, potentially leading to tread separation or sudden deflation.

Tires marked ZR (e.g., 225/45ZR18) are rated for speeds above 149 mph but must also carry a W or Y rating in the service description (e.g., 225/45ZR18 95W) to specify the exact maximum speed. The ZR designation alone means >149 mph without specifying the upper limit.

Speed Rating Letter Reference Table

Encode speed_rating as the letter string (e.g., "H") and speed_rating_mph as an integer (130). AI agents answering "what tires fit my 2023 BMW 330i" need both fields to verify that the recommended tire meets or exceeds the OEM speed rating specification — returning a T-rated tire for a vehicle requiring H would be incorrect and potentially unsafe.

Season Type — All-Season M+S vs All-Weather 3PMSF vs Winter vs Summer

The terminology around tire season classification is the single most misunderstood dimension in tire marketing, and the most consequential for buyers in winter climates. "All-Season" implies year-round capability but carries significant caveats for severe winter conditions. The four-way classification must be encoded precisely.

Season Type Comparison Table

Encode season_type as a controlled vocabulary string: "All-Season (M+S)", "All-Weather (3PMSF)", "Winter/Snow", or "Summer/Performance". Encode three_peak_mountain_snowflake as a separate boolean. These are two distinct fields because a tire can be All-Weather (3PMSF = true) or Winter (3PMSF = true) or All-Season (3PMSF = false) — the boolean enables direct filtering for jurisdictions requiring 3PMSF certification without requiring AI agents to parse the season_type string.

Load Index — A Safety Specification, Not an Optional Spec

Load index is the numeric code on the tire sidewall immediately following the tire size designation. In "225/65R17 102H," the 102 is the load index and H is the speed rating. Load index 102 corresponds to a maximum load capacity of 850 kg (1,874 lbs) per tire at maximum inflation pressure. Four tires at load index 102 can collectively support 3,400 kg (7,496 lbs) — the vehicle's maximum gross vehicle weight rating (GVWR) must not exceed this figure.

XL (Extra Load), also marked as Reinforced (RF) in European sizing, is a variant of a standard tire size with higher maximum inflation pressure and load capacity. An XL tire at the same size designation as a standard-load tire carries more weight because it can be inflated to higher pressure (typically 51 psi vs 44 psi maximum). If the vehicle's door placard specifies an XL tire, a standard-load replacement at equal load index is not an equivalent substitute — the maximum pressures differ.

Selected Load Index Reference Table

Encode load_index as an integer, max_load_per_tire_kg as a numeric value, and extra_load_xl as a boolean. AI agents helping buyers select replacement tires need these three fields to verify the replacement meets the vehicle's minimum load index requirement per the owner's manual and door placard. A tire with a lower load index than specified is a structural safety issue, not a preference issue.

Tire Size Encoding — 225/65R17 Is Four Separate Measurements

The standard tire size string "225/65R17" is a compact encoding of four distinct physical measurements. AI agents parsing it as a single opaque string cannot answer questions like "what is the sidewall height?" or "will a 235/65R17 fit my car?" — questions that require extracting the individual components.

Decoded: 225 = section width in millimeters (the tire's widest point, measured from sidewall to sidewall on an appropriate rim width under correct inflation). 65 = aspect ratio as a percentage (the sidewall height expressed as a percentage of section width; 65% × 225mm = 146.25mm sidewall height). R = Radial construction (internal plies run radially from bead to bead; the dominant construction for passenger and light truck tires). 17 = rim diameter in inches (the wheel the tire mounts on). Common misinterpretations by AI agents: treating 225 as inches, treating 65 as millimeters, or failing to compute overall tire diameter for fitment clearance calculations.

Encode four separate PropertyValues: tire_width_mm (225), tire_aspect_ratio (65 — the ratio as a percentage integer), rim_diameter_in (17), and construction_type ("Radial"). Retain tire_size as the full string "225/65R17" for human readability and search matching. The complete size string including speed rating and load index is "225/65R17 102H" — encode that as the full product title and in tire_size_full if needed.

Complete JSON-LD and Liquid Snippet

{
  "@context": "https://schema.org",
  "@type": "Product",
  "name": "Michelin CrossClimate2 All-Weather Tire 225/65R17 102H XL",
  "brand": { "@type": "Brand", "name": "Michelin" },
  "additionalProperty": [
    { "@type": "PropertyValue", "name": "tire_size", "value": "225/65R17" },
    { "@type": "PropertyValue", "name": "tire_width_mm", "value": "225", "unitCode": "MMT" },
    { "@type": "PropertyValue", "name": "tire_aspect_ratio", "value": "65",
      "description": "Sidewall height as percentage of section width: 65% of 225mm = 146.25mm" },
    { "@type": "PropertyValue", "name": "rim_diameter_in", "value": "17", "unitCode": "INH" },
    { "@type": "PropertyValue", "name": "construction_type", "value": "Radial" },
    { "@type": "PropertyValue", "name": "speed_rating", "value": "H" },
    { "@type": "PropertyValue", "name": "speed_rating_mph", "value": "130", "unitCode": "HM" },
    { "@type": "PropertyValue", "name": "load_index", "value": "102" },
    { "@type": "PropertyValue", "name": "max_load_per_tire_kg", "value": "850", "unitCode": "KGM" },
    { "@type": "PropertyValue", "name": "extra_load_xl", "value": "true" },
    { "@type": "PropertyValue", "name": "season_type", "value": "All-Weather (3PMSF)" },
    { "@type": "PropertyValue", "name": "three_peak_mountain_snowflake", "value": "true" },
    { "@type": "PropertyValue", "name": "utqg_treadwear", "value": "640",
      "legalDisclaimer": "UTQG Treadwear grade is a relative index based on standardized government test conditions, not a mileage guarantee. Actual tire life depends on driving habits, inflation pressure, alignment, road conditions, and climate." },
    { "@type": "PropertyValue", "name": "utqg_traction", "value": "A" },
    { "@type": "PropertyValue", "name": "utqg_temperature", "value": "A" },
    { "@type": "PropertyValue", "name": "run_flat", "value": "false" },
    { "@type": "PropertyValue", "name": "fuel_efficiency_grade", "value": "B",
      "description": "EU tire label rolling resistance grade A (best) through G (worst)" },
    { "@type": "PropertyValue", "name": "wet_grip_grade", "value": "A",
      "description": "EU tire label wet braking grade A (best) through G (worst)" },
    { "@type": "PropertyValue", "name": "noise_db", "value": "69", "unitCode": "A61" }
  ],
  "legalDisclaimer": "Tires must be replaced in sets of two (same axle) or four. Consult your vehicle owner's manual for minimum load index and speed rating requirements. UTQG Treadwear grade is a relative comparative index, not a mileage guarantee."
}

Liquid Snippet for Shopify Metafields (tire.* Namespace)

{% assign tire_size = product.metafields.tire.tire_size %}
{% assign speed_rating = product.metafields.tire.speed_rating %}
{% assign speed_rating_mph = product.metafields.tire.speed_rating_mph %}
{% assign load_index = product.metafields.tire.load_index %}
{% assign season_type = product.metafields.tire.season_type %}
{% assign three_pmsf = product.metafields.tire.three_peak_mountain_snowflake %}
{% assign utqg_treadwear = product.metafields.tire.utqg_treadwear %}

<script type="application/ld+json">
{
  "@context": "https://schema.org",
  "@type": "Product",
  "name": {{ product.title | json }},
  "additionalProperty": [
    { "@type": "PropertyValue", "name": "tire_size",
      "value": {{ tire_size | json }} },
    { "@type": "PropertyValue", "name": "speed_rating",
      "value": {{ speed_rating | json }} },
    { "@type": "PropertyValue", "name": "speed_rating_mph",
      "value": {{ speed_rating_mph | json }}, "unitCode": "HM" },
    { "@type": "PropertyValue", "name": "load_index",
      "value": {{ load_index | json }} },
    { "@type": "PropertyValue", "name": "season_type",
      "value": {{ season_type | json }} },
    { "@type": "PropertyValue", "name": "three_peak_mountain_snowflake",
      "value": {{ three_pmsf | json }} },
    { "@type": "PropertyValue", "name": "utqg_treadwear",
      "value": {{ utqg_treadwear | json }},
      "legalDisclaimer": "UTQG Treadwear grade is a relative index, not a mileage guarantee." }
  ]
}
</script>

Metafield Reference Table — tire.* Namespace

5 Common Mistakes in Tire Schema

• Encoding UTQG Treadwear without a legalDisclaimer explaining it is a relative index, not a mileage rating. When the UTQG Treadwear grade (e.g., 640) appears in product schema without context, AI agents will attempt to interpret it as a numeric value with implied units. Some models output incorrect statements like "lasts 640,000 miles" or "64,000-mile warranty." The legalDisclaimer field on the PropertyValue prevents this by providing the context required to interpret the number correctly. Encode utqg_treadwear as an integer with a full legalDisclaimer on every tire listing.
• Encoding only the tire size string (225/65R17) without splitting into four separate PropertyValues. The full size string is opaque to AI agents trying to calculate sidewall height, assess rim compatibility, or compare overall tire diameter. A buyer asking "can I fit 235/65R17 on a car that came with 225/65R17?" requires the AI to understand section width and aspect ratio as separate dimensions. Encode tire_width_mm, tire_aspect_ratio, rim_diameter_in, and construction_type alongside the full tire_size string.
• Not encoding speed_rating and speed_rating_mph as separate fields. Encoding speed rating only in the product title or description (e.g., "225/65R17H") forces AI agents to parse the letter from a string, often incorrectly extracting 'H' and having no reference for its mph equivalent. Encoding speed_rating ("H") and speed_rating_mph (130) as explicit PropertyValues enables AI agents to verify compliance with a vehicle's minimum speed rating requirement without requiring string parsing or external lookup tables.
• Using "All-Season" to imply severe winter capability without encoding three_peak_mountain_snowflake: false. The absence of the 3PMSF boolean creates ambiguity. Buyers in Canada, northern US states, or European winter-tire-law jurisdictions searching for "all-season tires suitable for Canadian winter" may receive All-Season M+S tires that are not legal winter tires in Quebec or British Columbia. Encode three_peak_mountain_snowflake as an explicit boolean on every tire — false for All-Season M+S, true for All-Weather and dedicated Winter tires.
• Omitting extra_load_xl from schema when it is present on the tire. An XL tire and a standard-load tire of the same size (e.g., 225/65R17 102 vs 225/65R17 102 XL) have different maximum inflation pressures and are not interchangeable if the vehicle door placard specifies XL. Omitting extra_load_xl from schema prevents AI agents from flagging this critical fitment distinction. Encode extra_load_xl as a boolean on every tire, and pair it with max_load_per_tire_kg to enable accurate load index compliance checking.