Racing line

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On racing tracks, black stripes of rubber on the tarmac from previous cars often indicate the racing line.

In motorsport, the racing line is the optimal path around a race course.[1] In most cases, the line makes use of the entire width of the track to lengthen the radius of a turn: entering at the outside edge, touching the "apex"—a point on the inside edge—then exiting the turn by returning outside.

Description[edit]

Racing line showing earlier and later apices in a standard corner

Driving the racing line is a primary technique for minimizing the overall course time. As the optimal path around a race course, the racing line can often be glimpsed on the asphalt in the form of tire skid marks.[2] A.J. Baime described its formation in the early laps of a race at Le Mans:

As the pack stretched out in single file—carving the black stripe into the pavement that was the racing line—the real competition began.[3]

Racing line optimization[edit]

A primary goal of the racing driver is to determine the optimum line around a race track. This optimum line may vary depending on whether a driver wishes to achieve a minimum lap time during a qualifying session, conserve tires and fuel, or fend off a pass from another driver during a race.

Race tracks are often broken down into separate elements such as standard corners, chicanes, double apexes, and straights. A corner can then be further broken down into the deceleration phase of corner entry, followed by the apex, and finally the acceleration phase during corner exit.[4]

Corner entry[edit]

The corner entry phase often begins with straight-line threshold braking where the goal is to achieve maximum deceleration rate. This is followed by the turn-in where the driver begins to steer the vehicle toward the apex. Traditionally, many drivers were taught to complete all braking before this turn-in portion and take a more circular path with a constant speed to the apex. Later, many racing drivers started to incorporate trail-braking into their corner entry. Trail-braking involves carrying brake pressure past the turn-in point which allows the forces generated by the tires to decelerate the car in a more optimized direction. This more optimized direction of force causes a vehicle to travel on an Euler spiral shaped path of decreasing radius to the apex. If done properly, this results in a higher average speed and lower elapsed time to the apex compared to the traditional circular entry.

Apex[edit]

In basic terms, the apex or clipping point is the point on the inside portion of a corner that a vehicle passes closest to. The apex can also be described as the point of minimum radius and slowest speed achieved in a corner. An apex can be defined as being an earlier apex or later apex. An earlier apex will reach the inside of a corner at a higher speed and with a larger radius than a later apex. A driver will typically choose their apex based on their vehicle's corner exit abilities with higher acceleration optimally requiring a later apex.

Corner exit[edit]

The corner exit phase begins at the apex when the vehicle begins to accelerate. The corner exit phase is often understood to be the most important aspect of a corner for minimizing lap times and so a driver will often focus on optimizing corner exit performance. A driver's goal during corner exit is to maximize the acceleration of the vehicle in the direction of the following straight. Vehicles with lower acceleration potential in a corner will typically achieve this by applying full throttle from the apex and taking a more circular path. Higher acceleration vehicles may be limited by wheelspin and will not achieve full throttle until the corner is nearly complete. This will create a corner exit path of increasing radius that will often mirror the Euler spiral-shaped corner entry path.

References[edit]

  1. ^ Bentley, Ross (2011). Ultimate Speed Secrets. Minneapolis, Minn: Motorbooks: MBI Publishing Company. p. 51. ISBN 978-0760305188.
  2. ^ Anderson, George A. (1993). Winning: A Race Driver's Handbook. Osceola, Wisconsin: Motorbooks International. p. 56. ISBN 0-87938-776-9.
  3. ^ Baime, A.J. (2010). Go Like Hell. Mariner Books: Houghton Mifflin Harcourt. p. 232. ISBN 9780618822195.
  4. ^ Development, Paradigm Shift Driver; Brouillard, Adam (2016-03-18). The Perfect Corner: A Driver's Step-By-Step Guide to Finding Their Own Optimal Line Through the Physics of Racing. Paradigm Shift Motorsport Books. ISBN 9780997382426.

External links[edit]