St. Helens and District Group of Advanced Motorists
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Anti-lock Braking System (ABS)
Have you ever thought what ABS means and what it does? Hopefully the next few lines will shed a little light on the subject and dispel some of the myths. Stopping is one of the more important functions you carry out as a car driver, more importantly is being able to stop in a controlled manner without skidding. Under normal braking conditions this is not a problem to most of us, but in an emergency it can all go a little "pear shaped". This is where ABS (Anti-lock Braking System) comes into its own.
Momentum
When you are driving along the wheels of the car are moving forward at the same speed as the rest of the vehicle. But when you come to stop you are slowing the forward movement of the wheels whilst the rest of the car still wants to move forward under its own momentum. It's just like putting a cardboard box on the back seat, if you stop the car suddenly the box caries on at the speed it was traveling at and slides off the seat. In the case of stopping your car it is the grip between the tyre and the road that allows you to stop safely and stops you skidding. The problem arises when the forward force of the car overcomes the traction the tyres have on the road and you skid.
Slip Ratio
The difference between the speed of the wheels and the rest of the car is technically known as the slip ratio. A ratio of 0% means the wheels are turning freely, whereas a ratio of 100% means you're experiencing one of the most terrifying moments of your life, you're skidding.
Using ABS
If you have ABS on your car, do you know what it feels like when it operates? One problem that arises with ABS is that people only use it in an emergency and when they feel the pedal moving up and down (vibrating) under their foot they panic and take their foot off the brakes. It's also worth knowing that when snow or gravel forms a wedge under your front wheels it can sometimes confuse the ABS system and your stopping distance may increase. Remember, drive safely and hopefully you will never need your ABS.
By Iain Grayson
Disclaimer: Driving is never a black and white activity, but full of grey areas, therefore neither I nor my fellow Observers in the St Helens & District Group of Advanced Motorists are liable for any consequences you may experience as a result of reading our advice. You are the driver. You should be in control of your vehicle at all times.
