ABS

[TheInsanity1234]

So, the Beeb continues to get it wrong for Dr Who - he's really Dr Whom!
Does he know? Back to driving now?

I read that as "Dr Wh-om" rather than "Dr Who-m" and was slightly bemused

[Graham Wright]

I'm so pleased I have been able to provoke yet another thread drift topic.

Anybody else like to try?

[Silk]

A bit like "heal and toe" and "double de-clutch".

Is your foot injured?

Both my feet are in perfect working order, thank you for asking.

[TheInsanity1234]

I'm so pleased I have been able to provoke yet another thread drift topic.

Anybody else like to try?

I had to look at the thread title to remind myself what we were discussing
Congratulations!

A bit like "heal and toe" and "double de-clutch".

Is your foot injured?

Both my feet are in perfect working order, thank you for asking.

What about your eyes, ears, mouth and nose?

[TripleS]

A bit like "heal and toe" and "double de-clutch".

Is your foot injured?

Both my feet are in perfect working order, thank you for asking.

Maybe the problems are all between the ears.

[TheInsanity1234]

Is your foot injured?

Both my feet are in perfect working order, thank you for asking.

Maybe the problems are all between the ears.

My ears ARE the problem in my case

[true blue]

I wouldn't presume to lecture on grammar, but having spent some time playing at Bruntingthorpe yesterday I can vouch for the fact that ABS is bloody marvellous! It's astonishing how quickly one can come to a controlled stop from motorway cruising speeds, and equally marvellous how responsive and stable a car can be under pretty severe evasive manoeuvres.

Perhaps this progress and technology malarky isn't so bad after all, though I'm still not entirely convinced by automatic gearboxes...

[Astraist]

Anti-lock braking systems (historically antiblockiersystem) have developed over the years and are not all alike. Over the years, they progressed from monitoring only one axle and from mechanically-induced "cadence braking", to a system that monitors each wheel individually and keeps it around the threshold of locking up.

Anti lock braking systems achieve three goals. The first and foremost is to retain steering control while braking, although steering is quite sluggish when the system "kicks" in. This feature has caused a series of collision when the system was introduced, since drivers were inclined to combine coarse steering with sharp braking, driving themselves off road.

A secondary aim is to reduce stopping distances. Early systems achieved this mainly in slippery conditions, where on a high-friction environment shorter stopping distances would sometimes be achieved even on four locked wheels. Nowadays, stopping distances are shorter in all conditions, aside from soft surfaces.

The third aim is to keep the car directionally "stable" on split-grip conditions. This is a lesser concern on private cars and vans (unlike lorries) made in the late eighties and onwards, and some systems even compromise this in sake of a shorter stopping distance.

ABS is also used in aircraft (it's historic origin) for shorter stopping distances and stable braking during crosswinds, and on motorcycles, allowing hard braking on either or both brakes without falling and, lately, to allow braking while cornering, much like it does on cars and trucks.

1. When the pedal starts pulse keep pushing down as hard as possible - you don't actually increase any pressures in the system (your foot is actually isolated from the brake hydraulics) but it stops the system reconnecting your foot to the pads.

So, in your opinion, if ABS is activated during braking on a slippery surface (where little pedal pressure is required to activate it), more pressure would reduce stopping distance further?

[martine]

1. When the pedal starts pulse keep pushing down as hard as possible - you don't actually increase any pressures in the system (your foot is actually isolated from the brake hydraulics) but it stops the system reconnecting your foot to the pads.

So, in your opinion, if ABS is activated during braking on a slippery surface (where little pedal pressure is required to activate it), more pressure would reduce stopping distance further?

No that's not what StressedDave said. He was suggesting you need to keep the pressure on the pedal (and not instinctively back-off) to ensure the ABS maintains maximum possible braking.

[jonquirk]

I think the point StressedDave is making is that if you lift off the brake pedal when ABS activates you remove the skid condition and ABS deactivates. If you haven't reduced speed sufficiently you are going to have to brake again, maybe causing the ABS to activate again.

You could end up going round in a loop of brake, ABS activates, back off brakes, ABS deactivates, reapply brakes, ABS activates and so on. Clearly it will take longer to stop doing that rather than just keeping your foot on the brake pedal and letting the ABS sort out how much retardation can be applied at each wheel.

[trashbat]

Thinking out loud... I find this a bit hard to qualify or quantify but I wonder if there is a narrow set circumstances where, upon triggering ABS, the best thing to do is, well, back off and try again later.

Obviously not as you're approaching stopped traffic, and for most of us here we don't go around unnecessarily braking, but perhaps on occasion it tells you about a localised loss of friction that you can avoid.

I'm kind of thinking about cycling here and how sometimes when having "friction issues" under braking, the best thing to do is come off the brake again and ride it out. I'm not sure it translates to cars very well. Maybe that's the whole point of ABS in a nutshell - that you don't need to do it.

[true blue]

As a cyclist (usually on skinny road tyres) I only back of the brakes if I lock up the back wheel. Then I'd be back on, with less pressure, trying to bring the speed down while maintaining control.

If I lock the front wheel up (usually once per year when there's ice and snow about) it's game over straight away.

If I had ABS on the bike, I don't think I'd ever need to back the pressure off.

[trashbat]

I've locked up my front wheel loads of times without crashing, be it on loose gravel when mountain biking, on ice, or painted lines on the road in the wet. It's usually recoverable. I wouldn't know whether the same can be said for road bikes.

[TheInsanity1234]

Is it good that I've never locked up the front wheel on any bike I've had?

I locked up a back wheel quite often, rather than the front, because of an experience when I was 5, I found that rear wheel mishaps were easier to get out of than front wheel lock-ups.

The only accident I've ever had on a bike was when I was 5 and I was riding down a hill on a nice, smooth stretch of tarmac, which then suddenly gave way to gravel, and the bike started to move around, so I just put the brakes on the rear wheel, and foolishly, the front too.

Suffice to say, I've still got a scar on my forehead from that mishap.

Never again, have I experienced the misfortune of front-wheel locking under harsh braking - I've learnt to lean back and put maximum weight over the back wheel, and keep the back wheel locked up, and try to steer around the obstacle, but if I just need to brake in the shortest distance possible, then I centre my body and try to keep both wheels as close to locking as possible.

[trashbat]

It's not something you really want to encounter because it's inherently unstable, but if you ride enough in varied conditions and sometimes asking a bit of the bike, it happens.

You have a much better continuous idea of surface grip on a bike though, especially on roads, and ride accordingly, so it's rare.