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All Disciplines of Motorsport – The Racing Line and Techniques

01/08/2011

OK, off we go with the next publication in our training and advise category. This time we are going to look at the racing line. Many people think they know their racing line, start on the outside of the corner, touch the middle and back out … Wrong ! yes that’s traditionally what a racing line is but there’s much more to it, what about sacrificing speed into a corner to maximize your speed onto the straight, and dealing with surface irregularities…

The racing line is the route a racing driver follows in order to take track corners in the fastest possible way. By using all or as much as needed of the available space on the track, cars can travel in a straighter line and travel faster before reaching the limits of grip. Determining the racing line is an essential skill to master for both track days and racing events.

The Apex:

To carry maximum speed through a corner, you need to take the route that minimises the tightness of the corner arc. This minimises cornering force and frees up precious grip for maintaining speed. This route tends to use the geometric apex of the corner and is  usually know as the classic racing line. In the diagram the turn illustrated is a constant radius 90 degree right hander and the geometric apex is exactly half way around the corner.

A Typical Corner:

Start at the outside edge of the track full throttle toward the corner. Take your foot off of the accelerator, start changing down through the gears whilst braking and as late as you can. To do this you obviously you need to know how good your brakes are. How quickly can you reduce your speed from 100mph to 40? How does your car behave when the front wheels are locked? All these factors determine your braking point. It’s a sensible strategy to brake earlier as you’re learning the track and your car, and progressively shorten the braking area as your experience grows.
Turn in at the correct point toward the apex of the corner. If you leave it too late and you’ll miss the apex, too soon and you’ll have to tighten your line mid corner. Remember that the apex may be further round the turn than you can see, so make sure you learn the track and the apex points before driving in anger.
Now accelerate out of the corner and aim your car back toward the edge of the track. The racing line doesn’t always needed to be used to its full extent if the car is not moving fast enough to need to utilize all of the road. Say you are approaching a very wide corner at a not so fast speed, it would be quicker to stay in the middle of the track and take the racing line in to the apex and then back out to the centre of the track than it would be to stay at the far edge and turn into the apex and then back out to the far edge.
A good way to get around a corner faster is to hang the front wheel nearest the apex over the kerb, you can gain a good amount of grip from a kerb, but don’t stray too far over. This will only gain a penalty or a spin.

Late Apex:

Oddly enough, carrying the highest average speed round corners may not actually be the quickest way around a track. If the corner leads onto a straight it can be better to take a late apex, straighten the car out early and get the power on for a high speed exit. This is generally regarded as the best strategy for racing, with a slightly lower entry speed but a faster exit speed. The amount of grip available is the factor which determines how late you can brake and apex.
The Slower The Corner the More You Need To Late Apex:

The faster the corner, the closer to the geometric line you should drive. The slower the corner, the more you need to alter your line with a late apex. The ideal line in the picture shows the tighter initial radius of a late apex meaning you will need to enter the corner slower. However it allows you to begin accelerating earlier, which will result in faster speeds on the following straight. Also you spend less overall time cornering and more time braking and accelerating.

Cornering Example:

 

  • Fast Line

The objective in this turn set is to maximize the exit speed coming out of the hairpin. The straight after the hairpin is longer than the one leading into it after turn 1, therefore maximizing speed coming out of turn 3 is more important than maximizing speed
heading into turn 2. To do this, the driver must drive a line which allows the earliest acceleration point. Planning the line by working the corners in reverse (because the highest priority one is the last one), the driver would want to late apex the entry to the hairpin to allow early acceleration out of it (show by the green arrow). To carry the highest speed possible into that late apex, the line to the apex must have as large a radius as possible (the radius prior to the green arrow). To accomplish a large radius entry into the hairpin, the left
hand bend of turn 2 must be entered with a very late apex, allowing the car to travel the far left side of the track through turn 2, then into a wide radius late apex for the hairpin. This line creates a very short straight through turn 2 into turn 3. Depending on the
speed of the car coming out of turn 1, the braking line through turn 2 is likely to be too short. Additionally, because of the sharpness of the hairpin, it will be easy to create understeer entering the turn from either too sharp a turn-in or not easing off the brakes smooth enough. This is a very tight corner set and a common mistake will be to brake very hard through the short straight in turn 2, jump off the brakes quickly for the turn-in to the hairpin, and sharply turn the wheel. This will create a lot of understeer, and slow the car significantly. To maximize the speed through the hairpin, it will be important to come off the brakes smoothly, and have a smooth turn in. To set up for this, most braking may have to be done before the turn-in to turn 2, the trail braking through the turn-in, and easing up
through the apex of turn 2. Entering the short little straight of turn 2 a little too slow is not going to cost as much time as entering it too fast, understeering and going wide through the hairpin, and delaying the point of getting back onto the gas. Such a mistake will cost several MPH of top speed down the following straight.

  • Slow Line

This line might be your first instinct. It carries higher speed into the corner set by taking a straight path between the two bends of turns 2 and 3. This reduces the initial turn-in, and delays the braking point. It will feel much faster heading into the turns, and that segment will indeed be faster than the fast line alternative shown. However, that fast entry line causes an early apex on the right hand bend heading into the hairpin. An early apex pushes the car to the outside of the track early to carry speed through the initial part of the corner. After that, a very tight turn after apexing is required to stay on the track. Compared to a late apex for the second bend, this requires a slower speed throughthe hairpin, and delays the point where you can get back on the gas. This line is faster for a short distance through turn 2, but is much slower along the entire straight after turn 3.

Trail Braking:

While the general rule for road driving involves separating braking and cornering where there is a period of coasting between releasing the brakes to the point you reach the apex of the corner and start to accelerate again. However with trail braking we can brake later and
continuing to brake into the early phase of the corner before the apex. This can help improve your lap times, but also pushes your car closer to the limits of grip. You will be able to see much more of the bend before you have finished adjusting speed and Forwards weight
transfer from braking enhances front tyre grip at the turn in point.
HOW TO TRAIL BRAKE?
Trail braking is quite a difficult technique as it requires a lot of feel and balance to be carried out correctly. However, with the knowledge, practice and perhaps an instructor it’s a new skill that can be learnt over a relatively short amount of time.

The main thing to think about is the Traction Circle. To reiterate a section of this fundamental theory: you cannot both brake and turn together, as much as if you carry out these events by themselves. Therefore, when you are entering a corner you must be reducing braking as you increase steering angle. When you are driving on track you cannot be thinking about numbers and percentages; it is
all about feel. You need to feel whether traction is about to break and this requires a good amount of practice. Always remember the fundamental rule of being as smooth as possible; be very gentle as you are removing the brake as you smoothly turn in. If you try to turn in too fast or with too much steering angle, you are guaranteed to oversteer and have a possible spin. Let that be a warning!

 

Track Surface Irregularities:
One factor that comes into play when finding the ideal line is whether the corner has any elevation changes, banking, bumps, or track surface changes. The general rule is this: most times, it is better to drive where the track offers more grip or traction to drive the perfect line. The same thing applies to any banking in a corner. If the corner is banked early in the turn and then flattens out, you will probably want to do most of your turning early on and then allow the Kart to follow a straighter path on the less banked part of the track. Focus on the most important corner first; and lastly the least important: The corner that is the most challenging or difficult can also be the most important turn. Usually, the most difficult corner will give your greatest improvement in lap time. Why? Simply because that is the corner you are most likely to be farthest away from having “perfected.” And, of course, if it is challenging to you, it probably is to your competitors as well. That means that if you can perfect it, you will have gained the most on the drivers you are racing against.
Slipping the Clutch:
Similar to the clutch kick in drifting however instead of spinning the wheels to send the car into oversteer we want to gain some power from the cars powerband. If you come out of a tight corner at low revs you can simply slip the clutch to and gradually release the clutch as you build up speed.

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