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ABS, ESC, And Their Effects On Vehicle Safety

The second last article I wrote was on the effects of different differentials and traction control systems.

These systems are designed to maximize the amount of power a vehicle is able to put down in less than optimal conditions. The following link will lead you to that article.


This article however will be less concerned with overall performance, and more concerned with overall safety.

Starting out with ABS. If you live in a part of the world that freezes, chances are you have had plenty of experience with ABS. If you live in a part of the world that freezes and don't know what I'm talking about, I'm talking about that weird pulsing feeling you get when you brake too hard.

The main idea behind ABS is that peak grip isn't achieved when a vehicles wheels lock up. It occurs just before braking free... or to be more precise, when they are slipping at about 10%... in layman's terms, for every 10 feet you move forwards, your wheels only rotate about 9 feet.

The trouble with getting this scenario however is that if you lock up your wheels, the overall force spinning those wheels dissipates, and it ends up that your original slightly overpowered braking force now severely overpowers the braking force necessary to start skidding, and as such your wheels will stay locked until you lower the braking force applied to the wheels.

Once you have sufficiently lowered the braking force on the wheels and they regain traction, they bite into the ground with their newly found traction, and you find yourself in a scenario where you are not braking to your full potential.

What ABS does is bring you past that critical lockup point numerous times ever second, keeping you in the critical braking zone longer than just simply locking up.

It should be noted however, that using basic abs is not the fastest way to come to a controlled stop. If a driver were to know their vehicle and the road conditions well enough, a driver can ride the thin line of traction keeping the vehicle just before skidding. Thankfully, most ABS systems only engage when the vehicles wheels have fully locked up and such skilled driving maneuvers are still possible.

In more advanced ABS systems, each wheel is monitored. Since each wheel always sees different loading scenarios, the brakes can be modulated so that each wheel is brought to its own unique lock up zone. In adverse conditions, this form of abs is superior even to a skilled driver. The skilled drivers limitation lies in that he can only bring it up to the critical point of one wheel since all wheels are tied to the same pedal. They have to cross their fingers and hope that the other wheels have as close as possible to a similar loading/grip scenario... which is never the case.

This advanced form of ABS also can potentially lead to the vehicle spinning out. For example if the car is braking and there is ice on the right hand side side of the road and pavement on the left. Bringing each of the wheels to their critical braking limits will cause the vehicle to spin to the left. Having your vehicle unintentionally spin left and into oncoming traffic is very dangerous. This is why these more advanced ABS systems are built in to another system. This other system is called ESC or electronic stability control.

ESC is a vehicles way of controlling the turn in rate of a vehicle. Most ESC systems control the turn in rate of a vehicle by selectively applying brakes and/or limiting power to certain drive wheels. By braking on one side, you can adapt a vehicles trajectory by causing it to over steer into a corner, or under steer thus inhibiting its ability to turn into a corner.

What this means in driving a vehicle with ESC enabled is that if you try to drift it, it will fight you tooth and nail, since it's trying to keep you going straight. This fighting will undoubtedly cause you to slow down as the brakes are applied, and if you're trying to drift a car... slowing down isn't the name of the game.

It also means, that if you are trying to turn harder then is physically possible, you will see under steer, and will no doubt skid off trajectory. Hopefully skidding off trajectory doesn't mean into another car, off the road, or into a wall.

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