Wheel fitment data.
Built into your product.

Getting access

1. Your company account is currently created by the FitmentCore administrator.
2. The administrator configures access status, request quotas and your key’s IP allowance.
3. You receive an API key. Save it securely: the full key is displayed only when issued.
4. Make your first request from the server that will run your integration.

Authentication

Use HTTPS and send the key in a request header. Both header formats are supported:

X-API-Key: YOUR_API_KEY

Authorization: Bearer YOUR_API_KEY

Use one format per request. Keep keys on your backend; do not embed them in a public browser app, mobile bundle or repository.

Base URL https://fitmentcore.com · Responses application/json

Build a vehicle picker

Get all catalog brands, then load all models for the selected brand. Both lists are alphabetically sorted and complete, without pagination. Each generation and year range is a separate model; multiple wheel fitments do not create duplicate model entries.

curl --get 'https://fitmentcore.com/api/v1/cars' \
  -H 'X-API-Key: YOUR_API_KEY'

{"brands":[{"brand":"BMW","bslug":"bmw","models_count":167}]}

Response excerpts show one brand or model; counts reflect the current catalog and may change.

curl --get 'https://fitmentcore.com/api/v1/cars' \
  -H 'X-API-Key: YOUR_API_KEY' \
  --data-urlencode 'brand=bmw'

{"brand":"BMW","bslug":"bmw","models":[{"model":"3 VII LCI (G20/G21/G28) [2022-2024]","mslug":"3-vii-lci-g20-g21-g28-2022-2024"}]}

brand accepts a brand slug or catalog name, case-insensitively, such as bmw or BMW. An empty value returns 400 invalid_brand; an unknown brand returns 404 brand_not_found.

Display the names in your brand/model dropdowns and pass the selected bslug and mslug to /api/v1/fitments/by-car. Fetch the catalog through your backend and cache the lists there to reduce requests. Catalog requests use the same API key, company quotas and IP allowance as fitment lookups and appear in usage analytics.

Find wheel specifications by vehicle

Identify the exact make and model, including its generation and year range. Alternatively, use the two slugs from the vehicle’s page URL.

curl --get 'https://fitmentcore.com/api/v1/fitments/by-car' \
  -H 'X-API-Key: YOUR_API_KEY' \
  --data-urlencode 'bslug=bmw' \
  --data-urlencode 'mslug=3-vii-lci-g20-g21-g28-2022-2024'

Replace YOUR_API_KEY with your issued key. --data-urlencode handles spaces, brackets and other characters in catalog names safely.

Find vehicles by wheel parameters

Start with a bolt pattern and diameter, then narrow the result with wheel width, offset and center bore.

curl --get 'https://fitmentcore.com/api/v1/fitments/by-wheel' \
  -H 'X-API-Key: YOUR_API_KEY' \
  --data-urlencode 'pcd=5x112' \
  --data-urlencode 'diameter=18' \
  --data-urlencode 'width=8.5' \
  --data-urlencode 'et=35' \
  --data-urlencode 'cb=66.6'

curl --get 'https://fitmentcore.com/api/v1/fitments/by-wheel' \
  -H 'X-API-Key: YOUR_API_KEY' \
  --data-urlencode 'mode=stag' \
  --data-urlencode 'pcd=5x112' \
  --data-urlencode 'diameter=20' \
  --data-urlencode 'wf=8' --data-urlencode 'ef=30' \
  --data-urlencode 'wr=9' --data-urlencode 'er=44' \
  --data-urlencode 'cb=66.6'

Matching allows ±0.5 inches for width and ±2 mm for ET. Bore comparison uses a 0.25 mm tolerance for catalog precision: a wheel bore more than 0.25 mm smaller than the vehicle hub is excluded. A larger bore may require a centering ring. Staggered matching checks the front and rear as one complete setup.

Reading the response

Wheel lookup returns results grouped by vehicle brand; each brand contains cars with model names and page slugs. An empty result list is a successful lookup with no compatible vehicles.

Wheel specifications such as diameter, width and DIA may be JSON strings. ET ranges are formatted text, such as 20–35 or ≤35, rather than a single numeric offset.

Request quotas & IP restrictions

Your company has per-minute and per-UTC-day quotas shared across all its API keys. Each key separately allows between 1 and 5 IP addresses, as configured by the administrator.

The first server IPs to use a key are registered automatically. A new IP over the allowance receives 403 ip_limit_exceeded. Ask the administrator to remove an old registration when moving servers. Treat each new server’s first request as an IP registration.

Quota windows reset at UTC minute and day boundaries. Requests that pass key, account and IP validation consume quota, including invalid lookup input and requests that exceed the quota. Requests denied by those earlier checks are logged without consuming request quota.

Errors & retries

{"error": "ip_limit_exceeded", "max_ips": 3}

Company accounts & subscriptions

Today, the administrator creates your company account, issues keys and manages billing status manually. Trial and active companies can use the API; unpaid or suspended companies cannot. Active accounts with a paid-until date expire after that UTC date.