Method & sourcing

Where the data comes from

Every vehicle on this site is identified by its manufacturer SKU (for example ARA7604V3T1). For each SKU we start from the manufacturer's own product page and its official exploded-view parts diagram for that exact SKU. We don't transcribe numbers by hand: a small extraction script reads the structured product data embedded in the archived product page and the part-ID list embedded in the archived exploded-view diagram, and writes out one JSON record per vehicle. Every displayed spec cell carries the source page it came from and the date we checked it.

Normalizing without changing the meaning

Manufacturers don't write specs consistently across generations — the same gear ratio might be written 4.3 on one generation's page and 4.30:1 on the next. Before comparing two generations, each value goes through a normalization step (numbers are parsed and compared numerically; short phrase fields like connector types are split on commas/slashes, sorted and compared as a set; free-text fields are case-folded and have "and"/"&", punctuation and extra whitespace ignored, so Painted, decaled and trimmed and Painted, Decaled, Trimmed read as the same value) so that a pure notation change doesn't get flagged as a real spec change, while an actual value change still does — Painted becoming Unpainted is still flagged, because the words themselves differ. This logic lives in one place in the code, and its tests include a set of cases built by sabotaging that logic on purpose — the point being to confirm the test would actually notice if the comparison broke, not just rubber-stamp whatever the code currently does.

Two kinds of row are flagged "not directly comparable" instead of being reported as a change. The first is product weight. When only one generation's weight is noted by the manufacturer as measured with electronics installed and the other isn't, the two figures aren't on the same basis, so we mark it rather than reporting a weight change that might just be a measurement-basis change. The second is a length-type dimension (the fields we compare in millimetres, such as length, width, height, wheelbase or track) that looks filed under the wrong label. We flag it when the two generations' figures differ by a factor of two or more and one of them equals, to the same rounding, a different dimension figure published for that model. In that case the number probably belongs to another field on the official page. We only add the note and leave the manufacturer's text as published.

Parts diffs

Exploded-view diagrams list a part ID for every component shown. We deduplicate each generation's list and compare the two as sets: an ID in both is "shared," an ID only in the newer generation's diagram is "new," and an ID only in the older generation's diagram is listed as not appearing on the newer diagram. That last category is a diagram fact, not a claim that the physical part was discontinued or is incompatible — a part can still be used even if a later diagram doesn't happen to list it separately.

The exploded-view diagrams label parts by number only, so we never guess a name from context. On newer comparison pages, a "system by system" section does show a name next to each changed part: it is the descriptive part of the address Horizon itself uses for that part's product page (taken from Horizon's published sitemap), with hyphens turned into spaces and the brand prefix dropped — nothing added. Parts are sorted into systems (gearing, differentials, shocks and so on) by keywords in that address; screws, bearings, shims and similar hardware are counted but left out of that section, and a part whose address we don't have stays a bare number. Every part number links to the manufacturer's own page so you can check the current name and fitment yourself, except where we requested that part number's page and the manufacturer's site returned "not found"; those are shown as plain, unlinked numbers.

What we won't do

• No sentence here is lifted from the manufacturer's marketing copy or manual text; each one describing a vehicle is composed fresh from the structured spec and part data. A check built into the release process compares every page against an archive of that manufacturer copy and blocks the build the moment it finds a long matching stretch.
• We don't reproduce official photos, logos, exploded-view diagrams or manual pages.
• Links to a part's manufacturer page are plain, un-tracked links to that part number's own page, labeled with the part number itself. We don't add store-style calls to action or figures around those links, and a build check enforces that.
• We don't publish a comparison built from data we haven't independently pulled and verified for both generations. If we only have one generation's numbers, the page says so instead of guessing the other one.

Staying current

Manufacturers revise spec pages after launch. Every page shows the date each side's data was last checked. Data older than a few months triggers an internal warning to go re-check the source before the next update, rather than silently getting stale.

Independence

Horizon Hobby, ARRMA, Losi and Axial have no hand in this project — they didn't build it, don't sponsor it, and haven't put their name behind it. It's an unofficial site, run on its own.