As there is an obvious demand for it, let's collect points that are either unclear or plain missing from Racer's official documentation site: Racer.nl Documentation Whether it's missing units for parameters, conflicting information, layout issues or the search function not getting you the desired results, you can post about them here and the community will try to help you out and clear things up. Eventually, we can forward our findings to Ruud, so improvements can be made. The more specific your posts are, the easier it will be to respond to them efficiently. Also, if you already have an idea on how to improve, better explain or expand on a topic - please include it in your post. Keep in mind that this is not meant to include actual bug reports, feature requests and the likes. I'll start: Missing unit on engine.rumble_amplitude, can (not) be found at http://www.racer.nl/tutorial/engine.htm#rumble Any ideas? It's listed as a force, so Newton probably fits the bill.