Traction Circle Question

Hi everybody, I am just about to finish the data analysis fundamentals course and have a quick question about the traction circle. Below is a screenshot from a session of a driver I have started working with. It looks like the driver is not using all the available grip during turn in and is then coasting as they get to max cornering gforce at the apex. Just wanted to double check if I am reading this correctly. Thanks in advance.

Is the datum point on the exit or entry of the corner? I would expect it to be on the exit due to the loading direction, but they do not have any acceleration on the vehicle at this point, so it may also be a transition from braking to coast on the entry to the corner.

Do you have steering angle logged? Understeer on entry can also look like this, especially on long changing radius corners.

Sorry the datum point is on entry, on the run into turn 6 at symmons plains. I don't have steering data as this is from a solo 2 running in an excel cup car.

I would expect to see a negative trace on the longitudinal axis that bleeds back from the peak to about where the compass pointer is, there should also be an increase in the lateral loading to that point that continues increasing to past the apex, and then bleeding back out as as the car straightens out and more longitudinal acceleration is generated.

That trace looks typical and normal to me. You have correctly diagnosed that the driver isn't "riding the rim" of the traction circle. The "coasting" phase at maximum cornering changes depending on the radius of the corner, the tire scrub also keeps the vehicle from accelerating longitudinally.

Definitely an opportunity to talk about trailbraking! The test is can you turn the wheel more and will the car respond? If it does, you have slowed down too much. Carry more speed into the corner with a lighter brake application, and test with the steering. If the car won't turn, then more brake until it does. Ride the traction curve!

Thanks for the input guys.