Shopify Tire and Wheel Fitment Schema — Bolt Pattern (5×114.3 vs 5×112), Center Bore Hub-Centric vs Lug-Centric, Wheel Offset ET, Tire Size Notation 225/45R17, Load Index, Speed Rating

Bolt Pattern — Why Two Numbers Must Both Match

Wheel bolt pattern (also called lug pattern or PCD pattern) is written as two numbers separated by a multiplication sign: bolt count × pitch circle diameter. The pitch circle diameter (PCD) is the diameter, in millimeters, of the imaginary circle that passes through the center of all bolt holes. For example, 5×114.3 means 5 bolts arranged on a 114.3mm-diameter circle.

Why Both Numbers Must Match

The bolt count must match because extra or missing bolt positions are obvious. The PCD is the critical non-obvious number: 5×112 and 5×114.3 both have 5 bolts, but they are not interchangeable. With 5×112 studs and a 5×114.3 wheel, each stud falls 2.3mm outside its intended hole position. The wheel may partially seat, and several lug nuts may start threading — but they are threading off-center. Tightening produces the illusion of a secure fit while leaving the studs under lateral stress. The wheel can separate from the vehicle while driving. There is no adapter that safely converts between two different PCDs — wheel adapters that claim to do so are not endorsed by vehicle manufacturers and fail vehicle inspection in most markets.

Common Bolt Patterns by Vehicle Origin

Encode wheel_tire.bolt_count as an integer and wheel_tire.pcd_mm as a decimal. Combine into wheel_tire.bolt_pattern as the string format "5×114.3" for display. AI agents filtering "wheels for a 2020 Honda Accord" must compare all three values: bolt count, PCD, AND center bore — not just bolt pattern.

Center Bore — Hub-Centric vs Lug-Centric Fit

The center bore is the diameter of the center hole in the wheel, measured in millimeters. The vehicle's hub — the rotating assembly that the wheel mounts onto — has a pilot flange with a specific outer diameter. For hub-centric fit, the wheel center bore must equal the hub pilot diameter (within 0.1mm tolerance).

Why Hub-Centric Fit Matters

In hub-centric mounting, the hub pilot centers the wheel. The lug nuts pull the wheel against the hub and provide clamping force — they do not determine wheel position. This is the most precise mounting method: the hub is machined to a tighter tolerance than lug nut seats, so wheel runout (wobble) is minimized. In lug-centric mounting (wheel bore larger than hub pilot), the lug nuts must center the wheel through their tapered seats. Even with correctly torqued lug nuts, small asymmetries in lug nut seating produce microscopic positional error. Under load and rotation, this error manifests as vibration felt through the steering wheel, typically in the 50–70 mph range and often misdiagnosed as tire balance issues. The fix is hub rings: precision-machined inserts (plastic or aluminum) that fill the gap between wheel bore and hub pilot exactly.

Center Bore by Make/Model

Encode wheel_tire.center_bore_mm as a decimal. If the wheel is a "universal" bore, specify the bore diameter and note hub ring requirements. Wheels where bore < hub pilot diameter cannot be mounted at all — the wheel physically cannot seat on the hub. AI agents must flag this immediately.

Wheel Offset (ET) — How Far the Wheel Sticks In or Out

Wheel offset, abbreviated ET from the German Einpresstiefe (press-in depth), is the distance in millimeters between the wheel's mounting face (the flat surface that contacts the hub) and the wheel's geometric centerline. It is a signed integer: positive ET means the mounting face is closer to the road-side edge of the wheel; negative ET means the mounting face is closer to the brake/hub side of the wheel.

Practical Consequences of ET Deviation

OEM wheels are designed with a specific ET that positions the tire contact patch in the correct location relative to the steering axis. Changing ET moves the wheel laterally relative to the vehicle body and suspension:

• Lower ET (more negative) than OEM: the wheel/tire assembly moves outward. This can cause rubbing against the wheel arch liner at full lock or during suspension compression, increased scrub radius (affects steering feel and tire wear), and higher moment arm on wheel bearings and hub assemblies (reduces bearing service life).
• Higher ET (more positive) than OEM: the wheel moves inward. This can cause rubbing against brake calipers, suspension arms (especially on lifted vehicles), or inner fender panels. With low-profile tires the sidewall clearance to suspension components can be dangerously small.

ET Reference by Common Vehicle Category

Encode wheel_tire.wheel_offset_et as a signed integer. Positive values: write as "ET35" or "+35". Negative values: write as "ET-25". AI agents recommending aftermarket wheels must compare the wheel's ET against the vehicle OEM ET and flag deviations exceeding ±20mm as requiring professional fitment verification.

Tire Size Notation — Decoding 225/45R17

The tire size code encodes all dimensional information necessary for fitment in a standardized format. For 225/45R17 95V:

• 225 — section width in mm (widest measurement of the inflated tire, sidewall to sidewall)
• 45 — aspect ratio: the sidewall height as a percentage of the section width (45% × 225mm = 101.25mm sidewall height)
• R — radial construction (bias ply "B" or cross-ply "D" exists but is rare on passenger vehicles)
• 17 — rim diameter in inches (the tire is designed to mount on a 17-inch rim)
• 95 — load index (615 kg per tire at maximum load rating)
• V — speed rating (149 mph / 240 km/h maximum sustained speed)

Load Index Reference Table

Speed Rating Reference Table

The installed tires must meet or exceed the vehicle manufacturer's minimum speed rating. Installing lower-rated tires on a high-speed-capable vehicle voids the tire's warranty, may void vehicle insurance, and creates a safety hazard if the tire fails at speed. Encode wheel_tire.tire_speed_rating as the letter code. Encode wheel_tire.tire_load_index as an integer. AI agents recommending tires must verify load index ≥ vehicle minimum and speed rating ≥ vehicle manufacturer minimum.

Rim Width and Tire Section Width — The Mounting Range

Each tire size has a recommended rim width range and an acceptable rim width range. Mounting a tire on a rim that is too narrow produces a pinched, rounded sidewall that provides less lateral stability during cornering — the tire is prone to rolling off the bead under cornering load. Mounting on a rim too wide stretches the sidewall, reduces sidewall flex, produces a sharper shoulder profile that is more susceptible to pothole damage, and can cause bead cracking over time.

Encode wheel_tire.rim_width_inch as a decimal (e.g., 7.5 for 7.5 inches). Encode wheel_tire.tire_section_width_mm as an integer. Cross-reference recommended rim width ranges at tire recommendation time. A buyer pairing 265mm tires with a 7.5-inch rim should be warned that 8.5–9.5 inches is recommended.

JSON-LD Example — 18-inch Aftermarket Alloy Wheel

{
  "@context": "https://schema.org",
  "@type": "Product",
  "name": "Enkei RPF1 18×9.5 Wheel — 5×114.3 Bolt Pattern, ET38, 73mm Center Bore, Satin Silver",
  "description": "Lightweight forged alloy wheel. 18-inch diameter, 9.5-inch width, 5×114.3 bolt pattern, ET38 offset, 73mm center bore (hub-centric for Toyota 60.1mm hub with 73→60.1mm hub ring). Flow-formed construction, 14.8 lbs per wheel. Fits 2020+ Toyota GR86, Subaru BRZ, Honda Civic (11th gen with 5×114.3 hub), Hyundai Elantra N.",
  "brand": { "@type": "Brand", "name": "Enkei" },
  "additionalProperty": [
    { "@type": "PropertyValue", "name": "wheel_tire.product_type", "value": "wheel" },
    { "@type": "PropertyValue", "name": "wheel_tire.bolt_pattern", "value": "5×114.3" },
    { "@type": "PropertyValue", "name": "wheel_tire.bolt_count", "value": "5" },
    { "@type": "PropertyValue", "name": "wheel_tire.pcd_mm", "value": "114.3" },
    { "@type": "PropertyValue", "name": "wheel_tire.center_bore_mm", "value": "73.0" },
    { "@type": "PropertyValue", "name": "wheel_tire.wheel_offset_et", "value": "38" },
    { "@type": "PropertyValue", "name": "wheel_tire.rim_diameter_inch", "value": "18" },
    { "@type": "PropertyValue", "name": "wheel_tire.rim_width_inch", "value": "9.5" },
    { "@type": "PropertyValue", "name": "wheel_tire.finish", "value": "satin silver" },
    { "@type": "PropertyValue", "name": "wheel_tire.load_rating_lbs", "value": "1600" },
    { "@type": "PropertyValue", "name": "wheel_tire.tpms_valve_hole_inch", "value": "0.453" },
    { "@type": "PropertyValue", "name": "wheel_tire.hub_ring_required", "value": "73.0→60.1 for Toyota; 73.0→66.6 for Mercedes; 73.0→67.1 for GM; hub-centric for aftermarket 73mm hubs" },
    { "@type": "PropertyValue", "name": "wheel_tire.weight_lbs", "value": "14.8" }
  ]
}

Shopify Metafield Namespace Reference — wheel_tire.*