Build A Faster Car - helping drivers engineer

The very first reason I looked into starting a site like this was, quite simply, to host a series of online suspension tools that I planned to write. I am writing them as a way of learning Adobe's Flash, since I've never used it before.

This is my first project with Flash and Adobe's ActionScript. So, I'm kind of relieved that I got it to work- it took me many hours to find out how to do some pretty basic things!

Anyway, if you haven't already noticed it on the front page, it's posted here:
http://www.buildafastercar.com/tech/Sway-Bar-Rate-Calculator

Comments? Is the user interface easy enough to use? I want these things to be as easy to use as possible.

One thing I have planned is to allow users to put select which car they have, then all the measurements pertaining to that car will fill in automatically. I expect this will be a lot of work, but that's the very next thing I plan to work on.