How do ABS systems work in stick shifts?

[mikebai1990]

Usually in an automatic car, the ABS helps to control pulsing of the brakes to safely come to a stop when at a loss of traction. It lets the brakes off as soon as the tires slip/lock-up, and rapidly pumps the brakes to continue this process until you come to a stop or you let your foot off the brake.

If that's the case, then how does ABS work in a manual? In a manual when you are braking in gear, and you unexpectedly lose traction because of snow/ice/loose rocks, your wheels will lock up, correct? However, if you are in gear, won't the locking up of the wheels immediately stall the engine? If that's the case, how would the ABS system function if the engine is stalled?

Since you're not supposed to gear into neutral or depress the clutch when braking, there is always a possibility of losing traction, and I think it's hard to know when you are suddenly going to encounter, say, black ice on the road when braking. In these situations, what is the driver supposed to do?

Perhaps I'm completely misunderstanding something, so appreciate the help

[jomotopia]

i am interested to learn more about this as well.

the best thing that i can think of right now is that the most common thing that happens is that only 1 wheel would lock up and due to a differential the other drive wheel wouldn't lock up and the engine wouldn't stall.

but i really have no idea and i was just wondering about this when i read your enginge braking / winter thread.

i suppose that maybe the ABS keeps the wheels from ever locking and hence the engine from ever stalling. this also may be why you are supposed to clutch in for a panic stop, since a panic stop is when you are most likely to lock the brakes.

[JackBauer]

The engine won't stall if you lock up the wheels. if you seize the wheels- doesn't mean the engine will also. However- you could stall it if yuo can't think calm under pressure, and start skidding on 4th gear, and don't drop it into the lowest gear possible or neutral. In which case- you would obviously loose ABS. which is why if your going to break that hard, and conditions don't allocate time for a down shift you should have the clutch pedal to the floor. This is assuming your ABS is glitching out- i've had many glitches with ABS systems. A properly working ABS will not lock you up.

[mikebai1990]

I've also heard that you should immediately clutch in during an emergency stop to avoid stalling. However, what would happen in a situation where you are braking regularly, not expecting any traction loss, but you suddenly hit a patch of "black ice" and your wheels lock up?

Your reasoning that not all all 4 wheels lock up certainly does make sense, perhaps that is why stalling doesn't occur.

I read some more on wikipedia about ABS, and here's what I found:

In gravel and snow, ABS tends to increase braking distances. On these surfaces, locked wheels dig in and stop the vehicle more quickly. ABS prevents this from occurring. Some ABS calibrations reduce this problem by slowing the cycling time, thus letting the wheels repeatedly briefly lock and unlock.

So according to this article, ABS lets the wheels lock-up before releasing them and continuing the routine of pumping the brakes. But then again, ABS usually works at individual wheels, meaning they wouldn't lock up all four wheels, which would again corroborate your reasoning that 1 locked-up wheel will not stall the engine.

edit: JackBauer, I was posting while you were, so I didn't see your post. So do you mean that all 4 wheels can lock up for a certain amount of time until the engine speed drops to 0, which is when the engine will stall?

[JackBauer]

Think about it. What is the purpose of ABS? The essential, bottom line, this is why we put it in the car purpose. what is it? if you said not to lock the wheels up, you get a cookie! if you hit a patch of black ice, don't bother clutching in, just drop it into neutral first, don't fight with the car on ice, but keep it in control, via proper braking, which with modern abs is alot easier. make sure you are not pumping the brakes if your car is equiped with abs.

[Prodigal Son]

The thing about winter braking is not just that traction is low, but that it is highly variable. Just braking for a stop light you could encounter snowpack, bare pavement, loose gransulated snow, and glare ice. You need to vary the brake force you apply as conditions change.

ABS is really good a handling this kind of variablility. Active engine braking is really bad at handling it since it does not vary braking force at all for conditions. Your left foot is somewhere in between the two. In winter, my technique is clutch in, brake, watch for changing surface conditions and modulate braking accordingly. In an emergency situation, hit the brakes, let the ABS do its job, focus on steering, and, if all else fails, hit something cheap.

[jomotopia]

In an emergency situation, hit the brakes, let the ABS do its job, focus on steering, and, if all else fails, hit something cheap.

you clutch in for this too right?

[Prodigal Son]

In an emergency situation, hit the brakes, let the ABS do its job, focus on steering, and, if all else fails, hit something cheap.

you clutch in for this too right?

Yes. At least, I would. I've never driven a car with a clutch and ABS. Actually, the reason that I bought a Saturn in my slushie period was because it had ABS and traction control in the lower end models -- in most other makes in the mid 90s, you only got ABS and TC in the high end models with sunroofs and leather seats. I hate sunroofs and leather seats. And I did not want to give up my clutch without getting ABS and traction control. A clutch is a traction control device.

But ABS is really for emergency braking. You still want to control the braking yourself over the variable road conditions I described, and you want the clutch in while doing it.

I think I have heard that ABS works best when the clutch is in, which makes sense. It isn't fighting with the engine if the clutch is in. And I think that some ABS systems do do brief lockups under some conditions to reduce braking distance while maintaining steering control, so you would definitely want the clutch in under those conditions, to prevent stalling.

So, I'm planning to take a winter driving course this year (if I can remember to book it in time) so that I can see how modern technology has changed the techniques I learned on the winter roads of Nova Scotia in the 70s and 80s before all these fancy gizmos came along. But until then I see no reason why the ESP system in my current car would require a change in how I use the clutch in winter driving.

[SteveUK]

Braking in a manual with abs is exactlty the same as in an automatic except at the last moment you depress the the clutch.

Slam on brakes
Wheels lock
ABS pumps the brakes, faster than you can do your self
wheels will lock and unlock very quickly
last possible moment clutch in to stop the car from stalling when you stop

ABS is designed to work like this when the roads are slippery.

NEVER depress the clutch at the same time only at the last possible second.

NEVER EVER change to neutral.

Here if you can't do this, you cannot pass your test.

[SteveUK]

When you are competent (ie able to pass your test) yes you can do brake then clutch. This is how an emergency stop should be done. With practice it is second nature.

If you can do nothing else, this is one thing you must be able to do. It is normally done at the begining of the test. The instructor will suddenly say "STOP" and you have to stop the car immediately and safely. If you get it wrong you automatically fail. Therefore, by the time you're driving around on your own with your licence you can do it.

[scionkid]

I got acquainted with my ABS in the 1st week of owning my brand new box. Some kid rode a bike in front of my car on the street that I lived and I was doing about 15 mph. The engine didn't stall until the very last moment 'cause I didn't clutch in (I was a stick shift rookie).

Tires don't have to be completely locked up to be skidding. If you're doing 70 and your tires are doing 40, you're skidding and the ABS will release the brakes. Even if your wheels are completely locked up, releasing the brakes will probably "bump start" the engine back on.

[jomotopia]

NEVER depress the clutch at the same time only at the last possible second.

NEVER EVER change to neutral.

can you please elaborate as to why? thanks.

[Paolo300zx]

I've also heard that you should immediately clutch in during an emergency stop to avoid stalling. However, what would happen in a situation where you are braking regularly, not expecting any traction loss, but you suddenly hit a patch of "black ice" and your wheels lock up?

Your reasoning that not all all 4 wheels lock up certainly does make sense, perhaps that is why stalling doesn't occur.

I read some more on wikipedia about ABS, and here's what I found:

In gravel and snow, ABS tends to increase braking distances. On these surfaces, locked wheels dig in and stop the vehicle more quickly. ABS prevents this from occurring. Some ABS calibrations reduce this problem by slowing the cycling time, thus letting the wheels repeatedly briefly lock and unlock.

So according to this article, ABS lets the wheels lock-up before releasing them and continuing the routine of pumping the brakes. But then again, ABS usually works at individual wheels, meaning they wouldn't lock up all four wheels, which would again corroborate your reasoning that 1 locked-up wheel will not stall the engine.

edit: JackBauer, I was posting while you were, so I didn't see your post. So do you mean that all 4 wheels can lock up for a certain amount of time until the engine speed drops to 0, which is when the engine will stall?

i was under the impression that ABS was designed to apply the brakes, and not when but IF the brakes lock up, it releases to avoid a skid... the general idea was to avoid locking them up, not trying to, and then letting them go.

[Bodder]

Not a scientist or anything but,

ABS is designed to keep the wheels rolling, but barely. There is greater friction if the tire is rolling than if it is locked up and just 'sliding' across the pavement, hence you would stop faster.

Thats what Im told and I believe.
Ian

[Paolo300zx]

Not a scientist or anything but,

ABS is designed to keep the wheels rolling, but barely. There is greater friction if the tire is rolling than if it is locked up and just 'sliding' across the pavement, hence you would stop faster.

Thats what Im told and I believe.
Ian

no, sorry thats wrong, the smallest stoping time is created while the wheels are locked up, it is just very dangerous. abs takes a longer stoping distance, however its more safe.