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]

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]

External links[edit]

• Elements of the racing line, illustrated
• Video: the physics of the racing line
• Tutorial: the physics of the racing line