Racing 101 - A thread covering race car physics, race terminology, and various race craft techniques.

Any professional driver will say the same thing, smoothness is a crucial aspect in racing for multiple reasons such as tire physics, traction management, and weight transfer. As a car is in motion, all these aspects affect how the car navigates around the course. Try to observe other faster drivers as often as possible and it will give you a rough idea of where the car should be at any given time but it's up to you to put the car exactly where you want it to be.


Traction Management - Knowing your car's limits and your tire's limits in addition to how they work is a crucial aspect in professional racing. Test the limits but never exceed the limits of the car and the tires as much as you possibly can until you know exactly what the car will do based on your steering, throttle, and brake input during all 4 driving conditions which are:

1) Accelerating
2) Threshold Braking
3) Balanced Throttle
4) Cornering

note: The colored circles around the tires in the diagrams below represent traction levels as indicated.

Yellow = Reduced Traction
Green = Moderate Traction
Red = Increased Traction


Acceleration - Under acceleration, only give enough input on the gas pedal to go as fast as possible without breaking road adhesion. Once the tires break traction even a little, you'll have to lift off and wait till the tires regain adhesion which will add time to your laps. It's also risky because it can unbalance the car and induce a spin due to the loss of traction in the rear.




Threshold Braking - Under braking, try to brake in a straight line as that will maximize traction on both front tires evenly while only giving just enough input on the brakes so that the tires are almost locking up but still rolling. This is known as "threshold braking" because you're braking on the threshold of the tire's capability. DON'T lock up the tires by applying too much brake pressure as it "flat-spots" the tires and can take a lot more distance to slow down plus it will prevent the car from turning while it slides.




Balanced Throttle - Balancing the throttle means maintaining a constant speed without accelerating or braking. It places the car in a "static speed / static traction" state. There are normally 3 times when a car is at static speed with static traction. It's when the car is at a dead stop, when the throttle is balanced and remains constant, or when it has reached it's absolute top speed. All 4 tires have an equal amount of traction as the weight is not shifting in any direction and is basically static which offers maximum tire adhesion to the track.




Cornering With Front Wheel Drive Cars - If you're in a front wheel drive car, you'll have to trailbrake slightly meaning you'll have to brake a little bit longer and for a split second while entering the turn as front wheel drive cars suffer from terminal understeer. As you brake for a split second longer while entering the turn, you're forcing the weight of the car on the front tires which adds more grip so the car can turn easier, it also unloads the weight of the car off of the rear tires which further helps the car turn by reducing grip which helps the car rotate. A common mistake most drivers make is using excessive steering input or over-turning the steering wheel. By turning the wheel too much, it generates heat and friction on the front tires while also binding the chassis.




Cornering With Rear Wheel Drive Cars - Rear wheel drive cars turn by a whole other method that doesn't involve trail braking as most rear wheel drive cars have to brake in a straight line then balance the throttle through the corner which will keep the outer tires in a static state that will maximize traction on those 2 wheels so the car can maintain a higher speed through the corner. Accelerating while turning will shift weight to the rear which reduces traction on the front tires making the car understeer. Braking while turning will unbalance the weight towards the front tires which will make the car oversteer as the added grip in front + reduced grip in the rear + weight transfer combined will induce the car into a spin in most cases. This is why you never brake if you're in a spin as it will only make the car spin even more.




Advanced Cornering Techniques - A more advanced cornering method requires the car to enter the turn at just the right speed while balancing the throttle so the car is on the verge of drifting yet maintaining adhesion. As the car is on the verge of drifting, you don't need steering input as you're controlling the car's angle by throttle only. This technique involves knowledge on slip angles and how much adhesion you can afford to play with without spinning out of control. If done properly, the steering input is basically zero, the throttle input is increased, and the car not only rolls better and faster through the corner, you're already on the gas and can hammer it at the exit. It's a technique that all formula car drivers have to master if they want to compete and can take years to learn.




Setups - Not all drivers and driving styles are exactly the same, what works for others may not work for you. A great example are 2 cars, both look identical in ride-height however the suspension setup can be drastically different. One car can have softer springs and a tall ride-height which is great for rally but not so great on a road track as you'd get more body roll and increased effect of weight transfer. The other car that looks identical can have stiffer springs with a lowered ride-height which would really plant the weight onto the tires while minimizing body roll which reduces the effects of weight transfer. The more weight transfer you have to deal with, the longer your car will take to correct itself back into a straight line. Less weight transfer equals more precise handling but at the same time, it can affect the car's ability to turn.


Adjusting Setups - Try adjusting one setting at a time but set it from the lowest setting to the highest setting so you can get an idea of what each setting does and how it affects the car, then you'll be able to adjust accordingly to your driving style. I have 3 setups per track, one for short races under 5 laps, one for long races over 20 laps, and one just for testing out settings without altering the other 2.

Next part will cover advanced cornering theories, bisecting corners, mapping out geometric apexes and real apexes, and trajectory arcs for decreasing, increasing, and constant radii.

to be continued...

This would be better suited in lfs beginners section

Quote from Sueycide_FD :

This would be better suited in lfs beginners section

You're probably right in that sense as it would be helpful to beginners for sure. The thread though is geared towards the highly technical side of professional race car driving, race craft techniques, race terminology, and race car physics.

I just figured the general racing forum would be the best place to post it as a few people tend to :arge: when something is posted in the wrong place... lol I actually think that's kinda funny. :biggrinfl

Interesting post

Always good to know how car behaves in order to drive it more efficiently and to know what to modify when something is wrong !

If I can give my 2 cents.

Actually everything start from tyres. When you are setting the car, what you want is to use as best as possible the grip your tyres can provide. I'll stay on the basics as tyres is the most complex thing on a car.

Maximum Acceleration

Tyres provide maximum acceleration both longitudinal and lateral. However you can't achieve maximum longitudinal and lateral acceleration at the same time. When you are accelerating in both direction (i.e. braking while turning or accelerating into a corner) you are actually reducing the maximum amount of acceleration you can have both in longitudinal axis of your car and lateral axis.

Actually acceleration (and also Forces) that a tyre can provide looks like this diagramm. x axis is lateral acceleration (negative = left hand turn, positive = right hand turn) and y axis is longitudinal acceleration (positive = acceleration, negative = braking).

http://www.temporal.com.au/fig2.gif

You can note that you can't have the same maximum longitudinal acceleration than deceleration. Indeed you are power limited by your engine.

How to maximize your car acceleration (and laptime)

In early days, drivers were trying to use only maximum longitudinal and lateral acceleration and not trying to combine both. That's mean braking in straight line, release brakes, turn in, apex, turn out, throttling.

https://wiki.eee.uci.edu/images/7/73/Ggdiagram3.JPG

In term of G-G diagramm (the one I have shown before), it looks like that :

https://wiki.eee.uci.edu/images/8/89/Ggdiagram4.JPG

Actually this graph isn't good. The fastest way to take a corner is to use the maximum combined acceleration. That mean that for any longitudinal acceleration, you should be as close as possible to the maximum lateral acceleration and exploit the previous graph.

How to do that?

Let's analyse a typical corner in term of that diagramm.

When you are at the end of a straight, your acceleration longitudinal is near 0 (maximum speed) and your lateral's one also. When you hit the brake, you reach maximal negative acceleration exactly as the example before. However, this time you will not release brake pedal before turn in point but stay on the brake while turn in. Of course you release it a bit not to lock up as your tyres can't manage the same deceleration. you wil then follow the lower circle of the graph until you hit the apex. On the apex, you hit the maximum lateral acceleration. From there, you can start being back on throttle and accelerate the car again. But once again, you will achieve that while turn out so as you decrease your steering angle (next step is about that ) you will be able to increase longitudinal acceleration and finally full/maximal longitudinal acceleration.

One last point, don't worry you almost do that everytime when you are driving quite quickly. I suggest you do some laps in hotlap mod and save raf file. Then you download LFS replay analyzer and plot the GG diagramm of your lap.

Case study : XRR at BL1

Here is an example of a lap of Sean Lyddon with XRR in BL1. Well Blackwood isn't really a symetrical track but still it can illustrate what I said above with a slight difference which is aerodynamics that increase the maximum acceleration and combined acceleration.

You got on it 1 straight braking (actually not completely straight as racing line is slightly turning), 2 combined braking through the corner, 3 maximum lateral acceleration on apex, 4 combined acceleration on corner exit. Note that it was early stage of setup development and that we got some issues with power control which cause some snappy oversteer (5 ) but that illustrate the fact that if you try to introduce too much longitudinal acceleration (i.e. accelerating full throttle too quickly) you will overload your tyre. On the other hand you can see on 6 the effect of engine on longitudinal acceleration. Indeed you lose you acceleration when speed is increasing (drag making it even worse).

http://imageshack.us/f/43/seangg.png/

It is important to highlight that all those different step can be long (i.e braking from 300km/h to 90km/h) or really short (step 2, 3 or 4). So even that powerslide isn't that big and Sean managed to do quite a decent laptime. It illustrate as well how power control can be an issue and that counter steer makes you lose some longitudinal acceleration. (See Pablo's post about what happen when cornering with throttle).

That's quite a complex thing to get but that's really the basic of everything. Setting the car is about trying to increase that circle radius and driving is about being at the limit of this traction circle.

New to lfs, learning on Blackwood GP, just switched from xf to xr. After reading this article I was able to shave 3 seconds off my PB with the xr, and now am close to my xf time. Still a noob-like time (1:47.77), but I at least feel I know what to work on. And I don't slide around so much. Thanks - this kind of article really works for me.

Advanced Cornering Theory: How To Calculate A Trajectory Path

When navigating around a race course, you'll encounter numerous direction changes and will have to adapt to each of them. Car positioning going into turns is by far one of the most important aspect in competition racing.

Most drivers only know about this general rule: "Outside, inside, outside" or "apex the turn". It's a method of using the most road possible to turn as little as possible making the car travel as fast as possible. Here are the actual physics and mathematics involved in calculating a trajectory arc.

There are several types of "arcs" as noted:

- decreasing radius arc is a turn which gets tighter or smaller
- increasing radius arc is a turn that opens up or straightens out
- constant radius arc is a turn that stays the same without deviating
- multiple arc radii are multiple turns that have more than one arc radius

Each arc has to be converted to an angle in degrees then bisected (cut in half) down the middle by dividing the turn degree number in half. Below is a 90 degree angle bisected into 2 halves, each being 45 degrees. Next step is to map a trajectory path that starts on the outside edge of the turn and allows the biggest arc radius possible while passing through the turn apex or inner corner, and leads back out to the opposing edge of the turn.

Most drivers will use the geometric apex as a marker to put the car over. Others use what's called the "real apex" which is slightly after the geometric apex. By shifting the apex and adjusting the arc radius to allow more room on the turn exit, the car will actually gain speed faster and is especially important if there is a long straight after a turn. If your car is able to accelerate even 1 second ahead of your opponent, that become several feet within the next few seconds time.

Going into turns fast is not as important as maintaining control of the car and having a stable yet quick exit out of the turns.





Advanced Cornering Theory: Trajectory Paths For S-Turns With Multiple Arc Radii

Anytime there's an S-turn leading to a long straightaway, exiting the S-turn is actually more important than entering it. Below is an image showing 2 trajectory paths.



The red path shows the most common line used in this corner which allows a large arc radius for both corners. The 2nd corner though requires the driver to take a smaller arc radius and won't allow the car any room to accelerate.

The yellow path shows a different line that sacrifices the first corner to position the car in a way that allows the 2nd corner to be taken with the largest arc radius possible and allows the car room to accelerate much sooner. As a result, it will exit the corner onto the straightaway at a higher exit speed and will make up for any time lost in the first section of the S-turn.



Advanced Cornering Theory: Exiting Fast Wins Races, Entering Fast Ends Races...

When you enter a corner too fast, odds are you're already losing time just trying to keep the car on the road and most drivers will anticipate this then dive to the inside for the pass. The ideal braking point & turn-in point depends on how much fuel you have, how worn your tires are in addition to their temp + track temp, and how hard you're pushing the car. The ideal racing line would be the shortest path from point A to point B and to win the race, you'll need to gain or lose momentum faster than your competition.

Final Turn - WE1 An example scenario of corner exit theory. In this section, the last turn starts very tight and slowly opens onto the main front straightaway. Taking this turn as fast as possible depends more on how long the car takes to change direction than it does on the moving speed the car goes through it.

Red dotted line: The braking and turning markers are too early causing the car to apex early and go wide since it runs out of road to use.

Green dotted line: The braking and turning markers are just right allowing the car to slow down enough to cut inside the racing line. Cutting inside at the exit of the turn is what will allow the car to accelerate sooner and will carry that speed onto the straightaway.

Black solid line: This is the normal racing line where braking points are a bit late or going too fast so it stays on the outside of the turn most of the time.