ElI5: What does traction/traction control mean?


ElI5: What does traction/traction control mean?

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When you are driving a car, there’s a limited amount of force that can be transferred from the car to the road, through the tires. This of course gets lower in wet weather, or really bad road conditions like snow or ice.

So traction is the ability of the tires to transfer force from the car to the road. For instance if you are accelerating quickly from a red light in wet weather, it might be that the driven wheels on the car begin to spin, because the force they are trying to transmit to accelerate the car exceeds the amount of traction the wheels have on the road.

Traction Control is smart electronics in the car which will lower the power being sent to the wheels so that the power being transmitted no longer exceeds the available traction, and instead of spinning the wheels, the vehicle accelerates as close as possible to the limit of traction available.

Traction is how much grip your tires have on the road. Not all tires are the same, and not all surfaces are the same.

Tires are like shoes in a way – if you have inappropriate footwear you will have less grip – if you’re using racing slicks on a drag strip, which is dry and sticky with no debris, there is a lot of contact between the tire and the ground, so you get the most traction with that flat piece of rubber…

But if the track is wet, those slick tires are now not capable of channeling water to the side. So the car will tend to glide across the surface, almost like ice.

So you end up with different sorts of tires that are optimized for different uses.

Traction control is a system that a car has that either cuts engine power or applies the brakes when it detects that a wheel is spinning freely. Some people misunderstand and think that traction control gives them more traction, which is not true. But something it does do is stop you from wasting the traction that you have – so it’s a little bit more difficult to lose control of the car.

The simple electronic traction features of cars can be described in 3 categories. These are ABS, TC, ESC.

ABS is Anti-lock braking system. It does exactly what it says. When you brake too hard, the wheels lock up and this reduces braking performance, and also it makes it impossible for you to change direction. When the wheels lock up, you’re still decelerating, but at a slower rate than the max theoretical amount. ABS is a mechanism that automatically engages and disengages the brakes very rapidly many times a second. This allows you to still have control, and at the same time help you stop. On casual road cars this system is quite simple (basically a simple on-off switch that’s very quick), but on advanced sports cars it can optimize braking by applying the exact braking pressure to maximize traction without locking up.

TC stands for traction control. It has the same idea as ABS, but works for acceleration. If you step on the gas too much, the wheels might get more power than what the tyres can handle, so instead of helping you go forward, they start spinning. This has two drawbacks. Firstly, instead of providing optimal acceleration, the loss of friction makes you accelwrate slowly. Also, it can cause you to completely lose control, especially on rear-wheel drive cars. TC cuts the power from the engine, so that the wheels stop spinning. The same thing applies in simple cars vs sports cars. On a Yaris, TC will completely cut the power for 0.5-1 seconds. This will slow the car very much. But on a sports car, the computer can modulate the power to provide optimal acceleration by keeping the wheels exactly on the grip limit. Electric cars are very good at this because they have complete control of power delivery.

ESC is electronic stability control. The basic system can brake individual wheels when it detects loss of traction. Usually happens when the car has understeer or oversteer. For example, if you try to go left but the car continues straight, ESC will try to decelerate the left-side wheels, to help rotate the car. Once again, this is simpler on slow cars, and much more sophisticated on sports cars or AWD cars.

In general, race cars have zero ESC, and may have ABS and TC depending on the race class. For example, F1 has zero assists. Spinning the wheels is extremely easy (1000 hp will do that to you), especially in the rain. Other series, like GT3, have ABS and TC and it performs very well.