Support this site

Every calculator here works without an account, without a signup and without a limit. The reference pages are complete rather than teased. That is how it is staying.

Running it costs money in the ordinary ways — a domain, hosting, and the time it takes to check figures and correct the ones that turn out to be wrong. A one-off contribution helps with that.

What contributions pay for

• Checking numbers. Platform records need re-reading as model years change, and every correction someone sends has to be traced back to the source before it is applied.
• Widening the catalogue. Each new size and each new platform is a small amount of research and a page that has to be genuinely worth reading rather than filler.
• Keeping the tools fast. Everything is computed at build time or in your browser, which is more work to build than calling somebody else's service and is why the pages load the way they do.

What it does not buy

Contributing does not change what the site says. It does not unlock anything, because there is nothing locked. And it does not buy an opinion on whether a tire fits your vehicle — that answer is not for sale here at any price, because it cannot be derived from the information this site works with.

If you would rather get something concrete for your money, the Fitment Reference Pack is a printable version of the reference tables, and buying it helps in exactly the same way.

Free ways to help that are worth as much

Send a correction. A wrong number found and fixed is worth more to this site than most contributions, because a calculation site with one bad figure is a calculation site nobody should trust.

Send a source. Several platform pages deliberately leave fields blank because the figures could not be confirmed. A pointer to a document that settles one turns a gap into a record.

Send a link. If a page here answered your question, saying so where the question gets asked is the single most useful thing anybody does for a small independent site.