---
title: "Drill down into a generation: per-vehicle modifications with OEM specs and fitment deltas for tire"
method: GET
path: "/v2/classified/by_tire/search/modifications/"
tags: ["Classified methods"]
---

# Drill down into a generation: per-vehicle modifications with OEM specs and fitment deltas for tire

`GET /v2/classified/by_tire/search/modifications/`

## Request

- Base URL: `https://api.wheel-size.com` (the document declares no server; this is the origin it was published from)
- URL: `https://api.wheel-size.com/v2/classified/by_tire/search/modifications/`
- Auth: API key in query parameter `user_key`
- TypeScript: <https://skmtc.dev/wheel-size/apis/wheel-fitment-api/docs/v2/classified/by_tire/search/modifications/get.ts> (a function with typed inputs; its response is checked against the schema)

Given a specific generation from the `by_tire/search/` hierarchy, returns individual trims/modifications with their OEM wheel and tire specs and per-vehicle fitment data.

Each result describes the vehicle's OEM wheel pair closest to the searched tire: its rim and tire specs plus deltas showing how much the searched tire differs from it: `ow_delta_mm` (overall width), `od_delta_mm` and `od_delta_percent` (overall diameter), and `ar_delta` (aspect ratio, percentage points). `load_kg` / `load_index` are the maximum over all of the vehicle's matching pairs.

Matching is identical to `by_tire/search/` — exact rim diameter, with tire overall width and overall diameter within ±2 mm — so against the same data every generation returned by the parent endpoint resolves here to at least one modification. The two responses are cached independently, so right after a catalogue update an empty result is possible. The ±2 mm window also bounds `ow_delta_mm` and `od_delta_mm` to ±2: they report how exact the match is, not a size change.

There is no `cb_diff_mm` here — a tire has no centre bore.

## Query parameters

- `section_width` integer, required
- `aspect_ratio` integer, required
- `rim_diameter` number, double, required
- `make` string, required
- `model` string, required
- `generation` string, required
- `limit` integer
- `offset` integer

## Response `200`

- VehiclesByTireGenerationReportOutput
  - `data` VehicleByTireData[], required
    - `slug` string, required: Identifier for the element. Value is a hash based on ID
    - `trim` string, required
    - `body` string, nullable, required
    - `production_start_year` integer, required
    - `production_end_year` integer, required
    - `regions` unknown[], required
      - unknown
    - `oem_rim` string, nullable, required
    - `oem_tire` string, nullable, required
    - `oem_rim_diameter` number, double, required
    - `oem_rim_width` number, double, nullable, required
    - `oem_rim_offset` number, double, nullable, required
    - `oem_tire_width_mm` integer, nullable, required: OEM tire section width, mm.
    - `oem_tire_diameter_mm` integer, nullable, required: OEM tire overall diameter, mm.
    - `oem_tire_aspect_ratio` integer, nullable, required: OEM tire aspect ratio, %. 82-series tires are reported as 82.
    - `ow_delta_mm` number, double, nullable, required: Overall width delta vs OEM, mm. Positive = searched tire is wider. Bounded to ±2 mm by the match tolerance.
    - `od_delta_mm` number, double, nullable, required: Overall diameter delta vs OEM, mm. Positive = searched tire is taller. Bounded to ±2 mm by the match tolerance.
    - `od_delta_percent` number, double, nullable, required: Overall diameter delta vs OEM, % of the OEM diameter.
    - `ar_delta` integer, nullable, required: Aspect ratio delta vs OEM, percentage points. Positive = searched tire has the taller sidewall.
    - `load_kg` number, double, nullable, required
    - `load_index` integer, nullable, required
  - `meta` ClassifiedMeta, required
    - `count` integer, required
    - `offset` integer, required
    - `limit` integer, required

## Changes

- **2026-09-17** `7fcbbffc6275`: 1 info
  - endpoint added

[Operation history](https://skmtc.dev/wheel-size/apis/wheel-fitment-api/changes/v2/classified/by_tire/search/modifications/get.md)

---

[API](https://skmtc.dev/wheel-size/apis/wheel-fitment-api.md) - [All operations](https://skmtc.dev/wheel-size/apis/wheel-fitment-api/llms.txt) - [OpenAPI document](https://skmtc.dev/wheel-size/apis/wheel-fitment-api/revisions/0283a9f8acf0?raw)