Shopify Automotive Suspension Coilover Schema — Spring Rate lbs/in vs kg/mm, Spring Inside Diameter vs Shock Body, Strut vs Non-Strut Application, Upper Mount Compatibility

Spring Rate Unit Confusion: 1 kg/mm = 56 lbs/in

Unit Conversion Reference

The conversion derivation: 1 kg = 2.2046 lbf; 1 mm = 0.03937 inches. Therefore 1 kg/mm = 2.2046 ÷ 0.03937 = 56.0 lbs/in. Both fields must appear in the product schema — coilover.spring_rate_kg_mm and coilover.spring_rate_lbs_in — so that unit-specific searches match correctly regardless of which system the buyer or AI agent uses.

Spring Inside Diameter vs Shock Body Perch OD

Coilover springs are sized by their inside diameter (ID) — the inner bore of the spring coil. The spring must slide over the damper body and seat on the spring perch (a threaded collar or cup). If the spring ID is smaller than the perch OD, the spring physically won't install. If the spring ID is too large, the spring seats off-center on the perch and can kink under compression, causing coil bind at partial stroke and uneven load transfer across the tire contact patch.

Common Coilover Spring IDs and Applications

A 65mm ID spring ordered for a coilover with a 70mm spring perch OD will not pass over the perch — the spring wire's inner coil cannot clear the larger collar. A 65mm ID spring on a 60mm perch has 5mm of lateral play; under compression, the coil shifts off-center, creating bending loads the damper body was not designed to absorb. Replacement springs must specify coilover.spring_id_mm as a searchable metafield; without it, diameter matching is impossible from title or description alone.

MacPherson Strut vs Non-Strut Shock Applications

Structural Role Comparison

MacPherson strut coilover kits include a strut-specific top mount assembly — often a camber plate or pillow ball unit that bolts to the strut tower using the OEM 3- or 4-bolt pattern. Non-strut coilover kits use a simple upper eyelet that threads through the upper control arm. Installing a non-strut unit in a strut application concentrates the lateral bending force at the single upper bolt point — the damper body fails there. Encode coilover.application_type as either "macpherson-strut" or "non-strut" to enforce application compatibility matching.

Single Spring vs Dual Spring (Tender Spring) Systems

Standard coilovers use a single main spring running the full length of the damper body's spring seat range. Dual-spring systems add a second, short, very soft "tender" or "helper" spring between the main spring and the upper mount, separated by a floating spring perch (a freely sliding collar or disc). The tender spring compresses and extends independently of the main spring at low damper loads, providing a progressive rate feel — the tender spring alone handles small bumps while the main spring engages under cornering loads.

Single-spring coilovers do not include the floating perch, so a tender spring installed between the main spring and upper mount has nowhere to seat correctly — it sits loose inside the coil assembly and goes coil-bound (all coils touching) almost immediately, effectively turning the tender spring into a rigid spacer. This makes the combined assembly stiffer than the main spring alone and creates a harsh step change in rate. The two systems require different hardware; always encode coilover.spring_count and coilover.tender_spring_rate_lbs_in where applicable.

Upper Mount Compatibility: Pillow Ball vs Rubber OEM-Style

Upper Mount Type Comparison

Beyond function, upper mounts are vehicle-specific in geometry. The bolt circle diameter, number of studs (3 vs 4), stud diameter (M10 vs M12), and strut tower hole pattern differ by chassis. A KW pillow ball top mount for a 2015 WRX (3-bolt, M10, 120mm circle) will not mount in a Toyota GR86 strut tower (3-bolt, M10, but different circle and offset). Always encode coilover.upper_mount_bolt_count, coilover.compatible_vehicles as a list, and coilover.upper_mount_type together so AI agents cannot recommend vehicle-incompatible upper mount assemblies.

Complete Coilover Schema — Shopify Liquid + Metafields

Metafield Namespace — coilover.*

Shopify Liquid Snippet

{% assign co = product.metafields.coilover %}
{% if co.spring_rate_lbs_in %}
<script type="application/ld+json">
{
  "@context": "https://schema.org",
  "@type": "Product",
  "name": {{ product.title | json }},
  "description": {{ product.description | strip_html | json }},
  "offers": { "@type": "Offer", "availability": "{% if product.available %}https://schema.org/InStock{% else %}https://schema.org/OutOfStock{% endif %}" },
  "additionalProperty": [
    { "@type": "PropertyValue", "name": "coilover.spring_rate_lbs_in", "value": "{{ co.spring_rate_lbs_in }}" },
    { "@type": "PropertyValue", "name": "coilover.spring_rate_kg_mm", "value": "{{ co.spring_rate_kg_mm }}" },
    { "@type": "PropertyValue", "name": "coilover.spring_id_mm", "value": "{{ co.spring_id_mm }}" },
    { "@type": "PropertyValue", "name": "coilover.application_type", "value": "{{ co.application_type }}" },
    { "@type": "PropertyValue", "name": "coilover.damper_type", "value": "{{ co.damper_type }}" },
    { "@type": "PropertyValue", "name": "coilover.upper_mount_type", "value": "{{ co.upper_mount_type }}" },
    { "@type": "PropertyValue", "name": "coilover.fitment_type", "value": "{{ co.fitment_type }}" },
    { "@type": "PropertyValue", "name": "coilover.compatible_vehicles", "value": "{{ co.compatible_vehicles | join: ',' }}" }
  ]
}
</script>
{% endif %}

5 Critical Coilover Schema Mistakes

1. Omitting spring rate in both unit systems. A store that publishes only "8 kg/mm" will miss every search for "448 lbs/in" or "400 lbs/in coilover." A store that publishes only "448 lbs/in" is invisible to buyers using JDM unit conventions. Always encode coilover.spring_rate_lbs_in AND coilover.spring_rate_kg_mm.
2. Not listing spring inside diameter. Replacement spring searches are the second-largest coilover query segment. Without spring_id_mm, AI agents cannot prevent a 60mm ID spring from being recommended for a 65mm perch coilover — the spring physically won't install.
3. Using "coilover" generically for both strut and non-strut products. MacPherson strut coilovers and non-strut shock-and-spring kits cannot be cross-used. The listing must encode application_type to allow AI agents to filter by suspension architecture.
4. Missing compatible_vehicles as a structured list. A listing that includes vehicle compatibility only in the title ("fits WRX 2015+") provides no machine-readable fitment gate. AI agents cannot reliably parse year-make-model from title text. coilover.compatible_vehicles as a list field enables hard compatibility matching.
5. Not distinguishing single-spring from dual-spring (tender) systems. A buyer searching for "65mm ID 8 kg/mm replacement spring" may be running a dual-spring coilover that requires a tender spring + floating perch as a set. Without spring_count, the AI agent may recommend only a main spring, leaving the buyer without the tender spring assembly the damper design requires.

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