Less Steering For Quicker Lap Times

Published: July 9, 2013

At Summit Point Main the conventional line through turns 7, 8 and 9 is to run a very late apex, roughly following the blue line below:

In order to execute the blue line, the driver typically applies significant steering input at the entry for turns 8 and 9, marked with arrows. Most of the rotation of the car happens at those turn in points.

I saw Spec Miatas take a different line through that segment which did not involve late apexes. Their line was roughly the red line below:

The red line is essentially "normal" apexes in 7, 8 and 9. The red line covers less distance than the blue line, especially in turn 8. Finally, the red line tracks out sooner exiting turn 9.

The trick to running the red line is to have a sufficiently high grip to power ratio. In a car that is able to run the red line flat out, the difference is 0.2-0.3 seconds.

A notable feature of the red line is faster track out in turn 9. Most drivers do not really need to use the entire track width at the exit of 9, which suggests that their mid corner speed is too low. However, low power cars like Miatas are flat out from the exit of turn 6, making it impossible for them to take turn 9 any faster. However, that extra corner exit grip can be used for steering past the apex, which is how we arrive at the red line - it cuts the distance traveled before the apex at the cost of "compromising" the line at the apex, but because there is grip available after the apex the car still fits into the track.

Eliminating substantial rotation at the entry of 8 and 9 removes scrubbing of speed that occurs there as well, leading to a higher speed at the apex of 9.

Lastly, turn 9 is uphill. Once the car is going up the hill there is additional grip available for the front tires, which can be used to finish the turn. Similar situation applies to the uphill turn at Lime Rock.

Tagged: advanced