What this is
Suspension and drivetrain calculators for anyone building an off-road vehicle, from a first weekend project to a shop’s customer builds. Enter your mounting points, tube sizes or gearing and see the geometry and loads, including how they change as the axle moves through its travel.
Where the math comes from
The 3-link and 4-link calculators follow the link spreadsheets that a generation of builders has trusted:
- the 3 Link Calculator v1.0 by Dan Barcroft;
- the 4 Bar Linkage Calculator v3.0 by Dan Barcroft and Greg Blanchette;
- its v3.1 suspension travel edition, revised by Chris Macock.
Their geometry is reproduced and checked value by value against the spreadsheets running in Excel. Where a spreadsheet takes a shortcut that breaks for some layouts, these calculators use the full physics. The reference page lists every such difference and why.
The coilover, crawl-ratio and axle-shaft calculations use standard mechanics; there is no spreadsheet behind them.
Use with judgment
Every result is an engineering estimate for the load case stated beside it. Real vehicles see impacts, fatigue and conditions no calculator captures. Use these numbers to compare designs and catch mistakes before you cut metal, not as a sign-off that a part is safe.
Privacy
- All calculations run in your browser.
- Your inputs are saved on this device only, so they’re there next time. Reset clears them.
- A share link carries your inputs in the part of the URL after the
#, which browsers never send to a server. - Visits are counted with Cloudflare Web Analytics: which page was viewed, the page that linked to it, your country, your kind of device and browser, and how quickly the page loaded. It never sees what you type, and it leaves out the part of a link after the
#. - There are no accounts and no cookies.