Braking with ABS
Sixty-five per cent of all cars now have ABS fitted and most countries require new models to have it as standard. ABS stands for ‘anti-lock braking system’, itself a misnomer because the system permits the tyres to lock partially during heavy braking. ‘Locking’ is when the brakes ask for so much slowing that a tyre stops turning altogether and drags along the road surface.
Road cars assign most of their braking force to the front tyres to benefit from their increased grip levels as weight shifts forwards during braking. A fully locked tyre provides no steering at all, and this is the point that ABS was designed to address. ABS works by sensing that one of the wheels has momentarily stopped turning, or is about to, so it reduces the braking force to that individual wheel momentarily to allow it to rotate again and retain enough grip to steer and continue slowing the car.
In simple terms, all you have to do with ABS is press the pedal as hard and fast as you can and keep the pressure on. Ironically, when you do push hard enough, the pedal vibrates underfoot as if you had just trodden on a Rottweiler’s tail, which can be disconcerting. So a lot of people take their foot off and have an accident.
That vibration simply indicates the car’s computer is doing its job by varying the brake pressures up to fifteen times per second. The pulsing will be accompanied by mini lock-ups and squeaks from the tyres as they scrabble between the stages of gripping, stopping and rotating again.
It’s a weird sensation, so it’s not a bad idea to try it out in the safety of an empty car park. Remember to check that nobody’s following you…
ABS filters the effects of panic by preventing major wheel lockups that might otherwise reduce your stopping power and allows you to ‘stomp and steer’. Stomp on the brakes as hard as possible and steer around the terror. It is critical that you keep your foot pressed hard on the pedal so the ABS can do its job, even when it comes to steering. The car will turn more lazily than usual so you’ll need to apply extra force to the wheel to make it obey.
For me, that’s where the honeymoon with this technology ends because having ABS onboard doesn’t mean you can stop in shorter distances. In fact, we were safer as a species before its invention.
In the 1970s, vehicle manufacturers were producing galactic-sized cars like the Ford Capri and Rover SD1. These big beauties lumbered around roads like bulls in china shops and squealed through corners at the behest of men with dubious ’taches, bell-bottom trousers and permed mullets.
It didn’t escape the attention of software engineers these mullets were getting bent out of shape whenever their owners were required to take evasive action on slippery roads. Skinny front tyres would lock up under braking and the driver lost all steering control as the fronts ploughed along the tarmac unless the leather loafer relinquished pressure on the centre pedal to unlock them again.
Back at work with a fresh set of paisley-patterned underwear, mullet man would regale his brush with death to his colleagues. Those stories kept people informed and alive.
Meanwhile, the cone-heads designed software to control the brake pressure without macho intervention. In the event of a driver panicking and pressing the brakes too hard, the tyres would only lock a little bit and retain some steering. At first there was a debatable safety improvement, but any benefit quickly evaporated. People felt safer so they switched off, followed the car in front more closely and started braking later.
The average crashing-in-a-straight-line-with-the-fronts-locked experience was replaced by a faster accident further around the corner, with a higher and more dangerous incidence of rolling over.
The tyres have fundamental limitations. If you exceed these with a combination of speed and heavy braking, the ABS won’t save you.
ABS-equipped vehicles are not designed to run without it. When ABS develops a fault the system usually sends too much braking to the rear, which can spin the car. Another fault is false recognition of a skid and the pedal goes solid without slowing you down. Been there, got the T-shirt.
If you see an ABS warning light on the dashboard it genuinely needs love from your mechanic.