In LRA I calculate the G forces by differentiating the position: this results in the center of the turn circle, and the lateral and longitudinal forces on the CoG. These need to be corrected for the slip angle of the car's body, using the forward vector and right vector.

To calculate the center of the turn circle at time T, LRA takes the position at <T - 0.05s> and <T + 0.05s> (formula). This also "averages out" some noise.

Your approach (calculating the G forces from the tyre forces) had crossed my mind, but I didn't follow that route, because:

1. It will give wrong results for the longitudinal force, because you need to subtract the force from air resistance -- which isn't in the RAF data. (At top speed the force on the wheels is pretty high, but acceleration is zero.) For the lateral force you should get a similar error, but smaller, because lateral drag will be very low, if LFS models this at all.

2. The tyre forces have big spikes when the wheel touches a kerb or bounces on the road surface. I expect the G forces derived from that will also be "spikey."

(I never tried it, though.)

If you want a good test for your calculations, use a RAF file from a lap at the Kyoto Oval. The banked turns there are an extra complication.

To calculate the center of the turn circle at time T, LRA takes the position at <T - 0.05s> and <T + 0.05s> (formula). This also "averages out" some noise.

Your approach (calculating the G forces from the tyre forces) had crossed my mind, but I didn't follow that route, because:

1. It will give wrong results for the longitudinal force, because you need to subtract the force from air resistance -- which isn't in the RAF data. (At top speed the force on the wheels is pretty high, but acceleration is zero.) For the lateral force you should get a similar error, but smaller, because lateral drag will be very low, if LFS models this at all.

2. The tyre forces have big spikes when the wheel touches a kerb or bounces on the road surface. I expect the G forces derived from that will also be "spikey."

(I never tried it, though.)

If you want a good test for your calculations, use a RAF file from a lap at the Kyoto Oval. The banked turns there are an extra complication.