One of the more useful channels to look at when using data to improve your riding is lean angle. This channel can show some interesting detail about what’s happening on the track, and it’s easy to visualize what is actually going on from looking at the data in graphical format. While many riders think absolute maximum lean angle is the most important number, there is far more information that is of value and can be utilized.
It’s not entirely necessary to have a lean angle sensor to obtain the required data, although a proper sensor is ideal. If you have a GPS system, or even one of the newer GPS lap timers such as the AiM Solo, lean angle can be calculated from lateral acceleration in a software math channel. Calculated lean angle is far from exact and does not take into account aspects such as the rider hanging off the motorcycle, but even still can provide plenty of information.
The attached chart shows several corners of Chuckwalla Valley Raceway in Desert Center, California. The top blue trace shows speed in mph (note the scale on the left) while the bottom red trace shows lean angle with its scale on the right. Here, lean angle is calculated from GPS-based lateral acceleration. Distance in feet is labelled across the bottom of the chart, while the individual corners and segments are numbered at the top. Turns 7 through 9 make up a right-left-right chicane; here you can see lean angle going to near 50 degrees in each turn, then returning to zero as the rider straightens the bike to vertical (zero degrees).
In each turn of a chicane or cluster of corners close together, the rider would ideally reach the same maximum lean angle. In turn 7, the rider reaches 50 degrees of lean, but somewhat less in turns 8 and 9. The cause may be a characteristic of the track, such as camber or available traction, but it is somewhat (and surprisingly) common that even expert-level riders will not quite reach maximum lean in the second turn of a chicane; the fix is simply a short discussion with the rider. In most cases, however, some further examination is required to determine the cause and any possible action.
How quickly the lean angle trace changes from maximum to zero and back to maximum shows how quickly the rider is transitioning from side to side between the corners. This value, usually referred to as roll rate, can be visually ascertained by looking at the data in time (rather than distance), or a math channel can be used to actually calculate a number. Here we see a roll rate of approximately 45 degrees per second between each corner. Note, however, that roll rate is dependent on speed; the faster the motorcycle is travelling, the more difficult it is to transition from side to side and the maximum possible roll rate correspondingly decreases.
Later in the lap, turns 10 and 11 are two long sweeping right-handers. Here, the lean angle trace would ideally ramp up smoothly and quickly to its maximum and remain at that maximum value for the length each corner. In turn 10, we see that the rider has accelerated through the corner (note speed is increasing) and lean angle must therefore decrease. In turn 11, there is a portion early in the turn where the lean angle decreases, then momentarily increases before returning to a fairly constant value. Again, these anomalies may be due to the track and not something the rider is necessarily doing wrong. In turn 11, for example, a look at the track map shows that section is actually two corners with a small straight in between, and the rider accounts for the slight straight with these changes. But perhaps a different approach would result in a faster lap time?
The lean angle channel is just one way to easily and quickly find areas of the track that need attention. Quite often more investigation into other data channels and some consultation with the rider is required, but the lean angle channel provides some easy reference and is usually a good place to start.
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