But, we’re getting ahead of ourselves a little bit. Every data analysis program will make us a scatter plot of our long. and lat. G forces. Some programs, like Traqview do it automatically. In others you have to do an X-Y Plot of the long. and lat. G force. Once we do this, a common name for the graph is a G-G Diagram. This diagram can tell us a lot about our driving and the car in transitional areas. We can learn much more than the often hear “Look, I corned at 1.5 Gs!”
As a driver, it’s easy to develop all of the cars G Force when just turning, braking, or accelerating. When we start to combine the corning with acceleration when exiting a corner, it’s harder but most of us are pretty good at it. The hard combination is braking and cornering – what we all think of trail braking. Most of us can do it but not anywhere near the limits of the tires (or car). The G-G diagram is what helps us to see how well we are actually trail braking and using all of the traction that is available to us.
The diagram gives us a quick visual method to check the shape of the points to see how we are doing using all of the cars traction. In the green diagram, you can see that the lower sides are almost inverted. There is good braking G force, but as soon as any lateral loads are introduced, the braking force decreases (less G force) very quick. This means the driver was not making full use of the tires traction abilities. The tires still had enough traction left to continue braking at a higher level while doing the same amount of cornering.
That’s not all we can get from this graph, but it’s a good start. It’s a far way from just seeing how hard we are braking or cornering. Now you can evaluate your transitions from braking to cornering. And since this graph is a good approximation for your cars traction circle, you can see just how much of the available traction you are using.
If you want to learn more, there is a really good section in Jorge Segers book available here.