Racing 102 - Optimal Racing Line

July 12, 2019

Racing 102 - Optimal Racing Line

Key video points:

The Racing Line - The path around the circuit that allows optimization of the car's handling abilities, and carries maximum speed through every corner and onto every straight.

Turn-In - The initial point on the track at which the driver turns the steering wheel to guide the car into the corner. 

Apex - The inside edge of the corner that determines the transition from going into the corner, to going out of the corner.

Track-Out - The outermost point on the exit of the corner where the steering input should become zero when exiting onto a straight, or when the steering input is used for the next Turn-In point if exiting into another corner.

Every race track that you encounter, both in the sim and in real life, will be a series of straight-aways linked by a series of corners. [Insert lame joke and smugface]... Your job as a driver is to make us of all the available pavement on a race track, in order to find the optimal path, or line; a line that allows you to optimize the car's handling abilities and carry maximum speed through every corner, and onto every straight. The rewards for mastering the line in conjunction with your other driving skill sets are faster lap times and, hopefully, race wins! Also, keep in mind that whether you are racing on an oval or a road course, these basic principles still hold true. So, we're now going to take a closer look at how to find the best racing line, as well as proper techniques for cornering.

Although you will find that not all corners are created equal, let's take a moment to discuss some terminology that we'll be using to break down a corner. First is Turn-in, or the initial point on the track at which the driver turns the steering wheel to guide the car into the corner. The Turn-in point varies from corner to corner, but it is vital, because it adjusts the trajectory of the car to guide it to the next important target; the Apex. The Apex is the term used for the inside edge, or bottom, of the corner that you are negotiating. The Apex is the heart of the racing line, and accuracy is important. You want to be within inches of the apex of each corner, every lap. The final portion of the corner is the Track-Out, or the last possible piece of asphalt at the edge of the track as you exit the corner. This is the easy part, because if you've executed the Turn-in and Apex correctly, the car will naturally want to travel to the Track-out.

The reason that these three terms are so important is because, when driving through a corner, if we accurately place the vehicle next to each of these three points, we will be travelling on the largest possible radius through that corner. This is vital, because; the larger the radius, the higher the speed that we can carry through a given corner

If you could take a car onto a large, open parcel of pavement, turn the steering wheel a quarter of a turn, or 45 degrees (Note: One quarter of a turn, is 90 degrees... but, this is the guy who finds it difficult to get the radius of a circle, and he's nice enough to blabber on in our videos, so give him a break!), and start driving on that constant radius, you would eventually reach a maximum speed based on the grip available from the tires on that vehicle. Holding on that same radius, any efforts to increase your speed would either create understeer or oversteer; most likely understeer, as the increased lateral forces cause the vehicle to overstep its grip threshold. Now, if you were to reduce your steering angle by as little as five or ten degrees, changing trajectory to a larger radius, you would note that the vehicle would be able to travel at a higher speed. This is the principle that we have to apply at every corner. It's important to use all the available pavement to create the largest possible radius, for maximum speed through the corner. 

Key video points: (Definitions self explanatory this time...)

Constant-Radius Corner

Increasing-Radius Corner

Decreasing-Radius Corner

One of the more common corners that you'll encounter is a constant-radius corner; named so, because throughout the corner, the radius never changes. For examples of this type of corner, take a look at Mazda Raceway Laguna Seca, which has several 90-degree corners to choose from. To navigate this type of corner, you look for the apex at the middle, and adjust your turn-in and track-out accordingly. You can see from the overhead visual, that the car gets to a definitive point at the end of the braking zone and adjusts trajectory at the turn-in, beginning the radius through the corner. If the turn-in is executed properly, you should be right on topic for the apex, and then on to the track-out. As you can see, we've created the largest constant radius possible; that means speed.

With an increasing-radius corner, the radius changes throughout the corner, starting small and growing at the exit of the corner. This type of corner tends to be a lot of fun from a driving standpoint because you can turn in a little early and pick up an early apex. But, you still end up with plenty of pavement on the exit of the corner as you're tracking out. This can mean big speed, and big fun, depending on the size of the corner. 

The decreasing-radius corner is a tough one to master. As its name implies, it is a corner that begins with a large radius that gets progressively smaller throughout. A classic example of a decreasing-radius corner is Turns 1 and 2 at Lime Rock Park. Although this is by name two corners, it's almost treated as one. The trick here, is that the initial radius of the corner will allow you to carry large amounts of speed but, as you get into the turn and the radius begins to shrink, you must slow the vehicle down in order to meet the grip threshold of the smaller radius. Notice how the vehicle can carry a lot of speed into the first part of the corner, but as the radius decreases, notice that there needs to be a speed adjustment at the halfway point in order to get through the smaller radius of Turn 2. The primary reason this type of corner is so difficult is because you have to slow down mid-corner, which disrupts the balance of the car and can cause both understeer or oversteer, depending on the vehicle being driven and your driving techniques. 

Your average 180-degree hairpin turn can be a unique challenge, and can be handled in a variety of ways depending on your driving style or the type of car that you're driving. On the face of it, it would appear that simply turning in and apexing in the middle of the corner would be the most efficient way to handle this type of corner, particularly if you're dealing with a fairly small radius. However, it doesn't necessarily give you the optimal exit speed. Another option for negotiating a hairpin is to treat it like two separate corners, with apexes at one-quarter and three-quarters distance around the turn. You enter the corner and pass the first apex, run wide in the middle of the corner, and rotate the car to aim it towards the second apex, and on to the exit. This is particularly effective if the corner has a relatively large radius, and the car that you're driving is pretty nimble and has good power to accelerate quickly. The third option, and most common approach, is to simply treat the hairpin like a late-apex corner. At the end of the braking zone, you'll turn in very late, and aim for an apex that is about three-quarters of the way around the corner. This allows you to get back to power early, and optimize your exit speed. However, you do have to be careful about using this method in traffic. Your slower entry speed will certainly make you susceptible to being passed by a competitor.

Key video points:

Type 1 Corner - A corner that leads onto a long straight.

Type 2 Corner - A corner situated at the end of a long straight.

Type 3 Corner - A corner that leads into another corner, and in which the racing line must typically be compromised to set up for the corner it leads into.

In this section, we've learned how to find the right racing line by locating the turn-in, apex, and track-out, as well as how to handle the various corners you can encounter on a given track. Now, we'll take a look at the types of corners found at tracks all over the world, and we'll put everything we've learned together.

A Type 1 corner is one that leads onto a long straight. These corners are critical, because you need to make every effort to achieve the highest possible exit speed in order to carry that speed down that straight. There's no better way to gain speed than when the car is traveling in a straight line, and the gas pedal is on the floor. Turn 10 at Summit Point is a great example, and a good one to practice. It's a classic constant-radius corner followed by a long straight. There are two items that you should analyze in replay mode in the sim; first, your speed at the track-out of Turn 10, and your speed at a given point at the end of the straight (ideally, just before you apply the brakes). These two data points should give you a clear picture of your progress. The more comfortable you get, the more your speeds will increase.

Type 2 corners are found at the end of long straights. Regardless of the radius of these corners, it is vital to consider the amount of time that you have the accelerator fully depressed on the straight. Traditionally, exit speed on Type 2 corners is not as vital as is focusing on optimizing your braking, and carrying speed into the corner. Turn 1 at Lime Rock Part is a great example particularly because, past the apex, you're going to need to reduce your speed to make it through the tighter radius of Turn 2. This turn is a great location to work on your late braking all the way to the apex of the corner. Be sure to review your data to check your top speed just before braking, as well as your speed at the apex of the corner. 

Sometimes called a "compromise corner", a Type 3 corner is basically a corner that leads into another. A great example of this is Turns 3 and 4, or the Left Hander and Right Hander at Lime Rock Park. Because you have TWO interconnected turns, you are unable to optimize the radius of both, so you sacrifice the optimum line through the first corner in order to be on the best possible radius for the second corner. At Lime Rock, because Turn 4 leads onto a straight, we choose a line through Turn 3 that's only purpose is to set us up for the ideal entrance into Turn 4. This is a great segment of track to practice on, and make sure you always check your speed at the exit of Turn 4 to rate your progress. Additionally, if you want to really challenge yourself, check out the double compromise corners of Summit Point's Turns 7 and 8.

So, with what you've learned about the race line and cornering, it's important to put it all together and make it useful on the track. Like learning any skill, getting a feel for the racing line is gonna take time and practice. That said, you should have a process in place to learn new circuits and new corners, that will help you to ramp up your learning curve relatively quickly. First, when tackling a new track, try to be methodical in your approach; start slowly, take in your sight picture, pick up reference points along the track and get a feel for the terrain for the first couple of laps. For each corner, start with a late turn-in and a late apex, leaving you with a lot of room at the exit of the corner. As you become more comfortable, gradually turn in and apex earlier until your track out point is right at the edge of the pavement. This will indicate that you're right on line!

As you won't have a coach sitting next to you every time you drive, another important aspect of your training is learning how to identify your mistakes. A symptom of turning in too early is that you'll need to turn the steering wheel more after the apex. If you're doing this, try turning in later, and keep the steering wheel steady all the way 'til track-out. Although we've talked about taking a late apex as part of the process of learning a track, it is certainly not the quickest way around. It's harder to identify when you're turning too late; you're general impression will be that the corner seems too easy after the apex. If you're not a little worried that you might go wide at the exit, you may be turning in too late. Try turning in a little earlier until your exit speed is maximized. Remember! As you're exiting the corner, you want to allow the car to travel to the edge of the pavement.

As you can see, learning the art of the racing line isn't exactly black and white. There are rules that apply to one track, that might not apply to another. Yet, there is no question that practice and experience will pay dividends in the long run. Cultivating and mastering this skill set will help you to quickly learn new tracks, and outsmart your competitors.

Well, they nailed it; the iRacing.com Driving School videos very clearly explain the development and reasoning for a driver to choose a specific line around track. You will notice, although they didn't come out and say it directly, that in order to put ANY of this to good use, the driver must be able to start out slow. It is incredibly important that once you decide to pursue a more professional attempt at sim racing, you choose to do so from scratch, and to start at the bottom rung. Heading to one of iRacing's free tracks, booting up the school circuit, and using the cones is a great way to settle down and get back to basics. Don't worry for a second about how fast you're going or what this lap time will be; just focus on turning in at the same exact point on this corner every single lap. Focus on hitting the apex points of your corner perfectly, no more than inches up, down, or across the road than the previous time around. Work on that smooth, effortless track out. Begin blending corners and start observing the differences in speed at the apex if you turn in at this point or that, and what that translates to at the end of the following straight. 

It should be abundantly clear even this early in the series how important programs like iSpeed, MoTeC, and ATLAS can be. Not only in determining setup changes and effects, but also for assessing the proper racing line, what you're doing wrong from a driving standpoint, and comparing different lines through individual corners. At this Second Stage of the Racer's Bible threads, you should now learn to use the tools given to you. Video replay analysis and data logging and analysis are crucial to benefiting from these exercise. Consider our Example exercise below, carried over from entry #1...


Example:
Mid-Ohio Sports Car Course, full circuit
Turn 4 - "China Beach"

Problem - You notice that in your practice session (because you are an intelligent racer and spend many laps in practice becoming consistent with your chassis and track combination and learning how to deal with traffic at this particular event), most of your competition can get through turn four and into turns 5 and 6 of "Madness" quite a bit faster than you. Using the first Racer's Bible entry, you consider vehicle dynamics and immediately characterize your issue as understeer; you then consider your Racing Line and work out a solution.

The Optimal Racing Line Solution -

You take what you know and understand to be understeer and consider what causes understeer from the racing line's point of view. After studying the video footage and checking your lap analysis tools on MoTec, you notice a tell-tale sign of early turn-in. Your steering inputs are increasing past the apex. Not only that, but instantaneous tire temperatures at the front sky rocket, and as you roll onto the throttle post-apex, you notice that each and every lap you lift off the throttle to reduce speed, then return to the throttle before beginning the turning sequence for turn 5. This problem is solved by turning in a little later. Turn 4 is a very important Type 3 corner at Mid-Ohio, as well as one of the few Type 2 corners and therefore a fantastic passing opportunity. It also leads into the "Madness" section of the circuit, comprised almost entirely of Type 3 corners, so nailing Turn 3 is extremely important for fast lap times and good race finishes. Your solution is worked out slowly and from the opposite side of the problem. You turn in late, and pick up a late apex at first, setting up for Madness much better. Eventually through data analysis you can reel the turn in point to a little earlier than your first changes, but later than what gave you the initial problem, to find the Optimal Racing Line that allows you to carry as much speed as possible into Turn 3 as well as out the exit of the corner and into the technical, flowing section of Turns 4 and 5. Well done.

 

 



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