A handy guide for your racing lines
Proper racing lines are the most important part of being fast, so let's analyse them to make you faster
You may think that the proper racing line is an easy thing to master. Brake near the outside edge of the track, hit the apex and accelerate while going near the outside of the track yet again. Sounds easy enough, but have you ever thought why even if you were doing all that you were slower than someone else. Ever wonder why you can brake later than someone in to a corner, but they will end up with a faster lap?
I know you have, so have I and many other people who have ever been on or at the side of a track. But while I may be a mediocre driver at best I have managed to figure out the thing with racing lines.
I will generally be talking about karts, which can be either gearbox karts or non-gearbox karts, but most of what applies to a gearbox kart, will also apply to a car.
First of all let's describe the differences between a gearbox and non-gearbox kart.
On the left is my KZ-2 gearbox kart, which has 6 gears and 50bhp. On the right is a non-gearbox kart which is a Rotax Max, a single speed kart with around 20 to 30bhp.
The gearbox kart
A gearbox kart will have a couple of gears, depending on the type of engine. It will also have brakes at the rear and front brakes as well. This type of kart, because of these things can brake very late in to a corner and accelerate very hard out of it. The idea with a gearbox kart is to stop it as quickly as possible, turn it and start accelerating out of the corner. The idea is that you make the brakes and engine do most of the work, because that is the strong side of those types of machines.
The non-gearbox kart
A non-gearbox kart on the other hand will have a single gear. This type of kart will only have a single brake at the rear and even if the kart is powerful. For example 30 or even 45-50bhp it won't be able to utilise that power in the same way that a gearbox kart can. Both because it has no brakes at the front and because having only one gear means that you can only get so much acceleration out of it. This type of kart in normally geared in such a way so as to hit its maximum revs just before you need to brake on the longest straight. This means that the main thing you need to concentrate on with this sort of kart is to maximise your corner speed. Because the more speed you carry through the corner, the easier it will be for the kart to accelerate afterwards. This applies especially for rental karts, which are the type of kart with the least power. So if you get a corner wrong in a rental kart, you will lose quite a lot of time.
So keeping in mind all that was said about the two types of karts let's see what that theory translates to on track.
Photo from Flickr / by Marco Verch Professional Photographer and Speaker
The white line is the one that the gearbox kart has to take. As you can see it makes heavy use of all the braking power the kart has. You can brake right in to the middle of the corner with this type of kart if you do it properly, as having front brakes means that the rear is less likely to slide. From around mid corner onwards you are back on the throttle and going through the gears. In the non-gearbox kart however as it only has a single brake at the rear, you need to brake in as much of a straight line as you can, as the back is more likely to slide and lose you time. In the non gearbox kart you would have to go for a later apex as well, because you will be trying to maximise the revs you will have at corner exit. Remember that you don't have the power of a gearbox kart to pull you out of the corner.
In a nutshell this shows that a in a gearbox kart you go for a policy of covering the least distance. Mid corner speed may be lower than some non-gearbox karts, but you will have the power to pull you out. Whereas with a non-gearbox kart you want to maximise the revs thought the corner, so you will have higher revs when the time comes for you to accelerate. The higher revs will make it easier for the kart to gain speed. If the revs fall too low as will happen with the sharp cornering approach of a gearbox kart, you will need lots of time to regain those revs again.
Furthermore as you probably know, speed lost exiting a corner means lots of speed lost at the end of the following straight. While a gearbox kart may be able to compensate for some of the lost speed, it will be more profound in a non-gearbox kart, which is heavily reliant on the technique of the driver. But the loss of speed on the straight via a bad corner exit will be analysed later in the article.
The complicated bit on track
Photo from Flickr / by Marco Verch Professional Photographer and Speaker
As I said, this is the complicated bit. Connecting two corners together in order to get the maximum out of the track and kart is easier said than done. The gearbox kart can always take the shorter path from one corner to the next and count on superior braking power and horsepower. However it is not so with a non-gearbox kart. If you look at the line of the non-gearbox kart between the two corners you may think that it's a bit odd. It certainly looks that way, but what the driver of that kart is doing is maximising the revs he can get between the two corners. Then he straightens off the line in order to brake as much as possible in a straight line. That is again followed by a late apex and an exit on to the straight.
Geometric vs Ideal racing line
Geometric line vs Ideal racing line / Images by M. Petkov
Nearly all the difficulty in understanding the racing line up to this point was placed on the shoulders of the non-gearbox class. But now let's place some difficulty with the gearbox class and car drivers. What you can see above is two images showing a difference in speed. Where that difference comes from is the use of either the geometric or ideal racing line for the previous corner. If you use the geometric line, that means that you will place the apex of the corner right in the middle of the corner, whereas if you use the ideal line, you will place the apex slightly after the mid corner point. This is important, because as you can see the difference in speed may be quite big depending on how long the straight after the corner is. Hence why one is called a geometric line, because it is mathematically correct for the specific curve and the other is called a racing line, because it takes in to account the loss of some corner speed but the gain of a lot of speed on the straight.
You may have to compromise one corner in order to get a better exit for another one, or adjust your line to get a better exit. What all racing lines come down to is the maximum speed on to a straight. The more speed you can carry on to a straight the better the lap time will be. Of course you can't give away too much minimum corner speed. That may even be more difficult to do in a non-gearbox kart, especially a rental kart, because you need to make sure to keep the revs up through the corner as well. So the racing line will be heavily dependant on the track layout and the vehicle you may be using, but use what has been said above and try to work on your lines. It's best to remember that a bit of speed lost on corner entry isn't that much to how much you will lose if you mess up on corner exit and carry that loss on to the straight.
How it looks on track
In this first video you will see a red and blue kart. The red one is a non-gearbox that completely missed any racing line but look at the blue kart, which is a gearbox kart. Notice the line it takes and compare it to the kart in the second video below.
This second video is a slow motion video of a non-gearbox kart cornering the way it should. Notice the late apex.
Let me know what you think. Have you ever driven on track? What was the experience like? How fast do you think you can go?