One of the most fundamental aspects of safe and fast driving is making sure that you’re driving on the “proper line.” There are theoretical and geometrical lines to take through corners on the road and turns on the race track. Which is the best one for you? If you have two identical radius 90 degree corners, is the line the same through each one? Not necessarily. This is where the theory gets complicated just as quick as the geometry.
The “line” is made up of a curve that includes multiple points of reference. In fact, before you even start turning in, there’s usually a braking point and zone before you get to the “turn in” point. After the turn in point you get to the apex, and from there you exit at the “track out” point. By connecting the dots in a smooth and wide radius, this allows the driver to lessen the steering input. This allows for more mid-corner speed which ultimately leads to a lower lap time.
If you have an X long straightaway followed by another X long straightaway, with a 90 degree corner in the middle, the geometrical apex of the corner and the largest radius might be very close to the theoretical best line through the corner. However, it also depends upon what kind of car you’re driving and where you’re driving it. If it’s a high-horsepower car, you might want to move that apex point further away (later in the corner) from the geometric point.
What are the results of hitting your apex early or late? If the corner is increasing radius, an early apex is okay. If it’s a “textbook” 90 degree or a decreasing radius corner, the results of an early apex can be severe. Once you’ve turned into an apex at speed, there’s very little correction that can be made if you’re not hitting it within a few inches. If you apex early, you will run out of room, or roadway position, at the exit. This typically brings up two responses – the first being that you lift off of the throttle because you’re carrying too much speed. The second being that you turn the steering wheel more to avoid driving off the outside edge of the road. Both of those actions combined can create a TTO, or Trailing Throttle Oversteer. The result is that at this point you can fly off the road surface backwards, or if you’re racing on a grand prix street course, you can hit the concrete barrier.
If in contrast you apex late, you will leave excessive room on the roadway position at the track out point. It’s safer, and also slower. It’s also a great way to start to learn a track or an unfamiliar mountain road.
In Part II, we’ll take a look at turn combinations and other aspects of driving the line.
By Larry Mason
Copyright © 2021 Larry Mason