Traction Control is as it says – to control traction, as best as it can in the conditions it encounters! It must be said that traction control won’t save you if you run out of talent at higher speeds and it will probably scare some drivers when it kicks in at low speeds that makes them react suddenly that causes an accident anyway!
For this article, I’m going to concentrate on the electronic type – like many automotive ideas, mechanical “traction control” has been around for over 80 years thanks to Ferdinand Porsche wanting to improve the abilities of a racing car and working with ZF to design the Limited Slip Differential. This idea, in probably every production car built today that uses a “diff”, enables the slipping wheel to receive less power thus enabling the wheel with traction to move and hopefully allow the other wheel to find grip.
Maximum traction is obtained when the tyres on the drive wheels just begin to slip against the road surface. Maximum traction for braking is between 14% and 20% slippage. For maximum traction during acceleration, the electronic systems on today’s cars allow up to 30% slippage.
Electronic traction control works by doing a few things that depend on the situation. It could apply brake to the wheel that has lost traction, it could reduce power by breaking the electricity to one or more spark plug or it could close the throttle (depending on the throttle mechanism used). The idea is to slow the vehicle (or specific wheel) enough for the rubber to grip again – without any sudden change of direction by the driver.
My research suggests that Buick were the first to get a production ready electronic system to market. They brought out a version called MaxTrac in the early 1970s on the 3rd series Riveria. This had sensors on the front wheels and the transmission. It was a rear drive car however the MaxTrac was using the speed of the the front wheels to measure whether the front and back speeds were in sync. An electronic control unit then adjusted the ignition to reduce power to the rear.
Traction control is often connected with the Anti-Lock Braking System and Electronic Stability Control and is especially useful on a front wheel drive car where the wheels are trying to do too much, i.e. steer and provide power through the rubber. Incidentally, on a motorcycle you are taught that the front wheel should only do one thing at a time: either steering or braking, never both at the same time. I believe the same principle for driving a car should also apply – especially on a front drive: power and steering gives grip, braking and steering loses grip.
Development of traction control has typically been as a part of a wider safety control system for luxury cars which then flows down as the cost of components reduces. Today most cars except for really cheap models have some form of electronic system and if you’re lucky you can switch it off to take back control of the vehicle – provided you know your limits and the car’s. I personally think that many drivers assume that the electronics will save them in a crisis, which it may. However, it doesn’t replace skill and ability to know where to look and what to do quickly should the car get out of shape. These are human skills that no computer can replicate.
I have traction control, ABS and other electronics on both the car and motorcycle. For the bike I found that the traction control and ABS needed to be switched off on dirt roads – where you would think that they would be useful. However the ABS doesn’t allow the front wheel to get to the maximum braking point and the traction control cuts the power when slippage is detected and this then means that the ride is rougher as you try and get the power back up, making the ride harder.
For the car, the traction control is in the background and you only notice it when a little dashboard light flashes to say it is doing something. However, again it reduces my input because I do not feel the weight of the car moving and so do not experience where the limits of the chassis or tyres are. This reduces my ability in a major incident. For normal driving it is OK to have it on (when in reality it does nothing!), for fast road use or track days it has to come off so that I can learn how to handle the car in different situations and be able to react quickly to them.