Racing 101 - Race Car Physics

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.

I'll create a section soon on cornering theory but wanted to explain complex-S turns as promised. 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.

only just noticed this section - thanks its a very informative guide which gives a good insight into the physics

Thanks B as I appreciate it! :DI wanted to share the knowledge I had to pay for in racing schools so others can also benefit from it! Here's one of the graphics I made for the cornering theory section. It's fairly complex but the images make it easy to understand lol.


   Advanced Cornering Theory: How To Calculate Trajectory Paths

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.

very good information actually
thank you RFX  

Final Turn - WE1

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.