Braking with ABS - OK, or avoid at all costs?
Discussion
Morning All,
I know all the reasons for not locking up the wheels under braking in a car without ABS, but with the vast majority of road cars now having it, what is the best approach to take?
Let's say I can judge by braking to either 95% or 105% of the available grip. Take the brakes to 95% and I'm slowing without ABS. Take it to 105%, and the ABS kicks in. Will I lose speed faster at 95% or 105%? Will I have less control and stability at 95% or 105%?
If I'm pushing hard, I tend to brake to the point of getting the first judder of ABS, take this as the maximum braking force and back off slightly to cut the need for ABS. Is this right or wrong?
I know all the reasons for not locking up the wheels under braking in a car without ABS, but with the vast majority of road cars now having it, what is the best approach to take?
Let's say I can judge by braking to either 95% or 105% of the available grip. Take the brakes to 95% and I'm slowing without ABS. Take it to 105%, and the ABS kicks in. Will I lose speed faster at 95% or 105%? Will I have less control and stability at 95% or 105%?
If I'm pushing hard, I tend to brake to the point of getting the first judder of ABS, take this as the maximum braking force and back off slightly to cut the need for ABS. Is this right or wrong?
I was told (by Andy Walsh) to go straight to the ABS then back up to the bite point, in a straight line you can jump on the brakes but the transition off the brakes back onto power needs to be smooth (as you're likely to be turning or about to).
Surely if you use your 105% point you'll run out of track? Always leave a bit of margin for error imo.
Surely if you use your 105% point you'll run out of track? Always leave a bit of margin for error imo.
I do hope you are not relying on use of maximum braking on the road. But assuming that you are playing in a safe environment:
On the Andy Walsh Car Limits DVD, he demonstrates that he can stop in a shorter distance using 'Threshold Braking' just before the ABS cuts in than using the ABS. But he achieves this in a car and on a surface he knows very well - and it is quite an old car which does not have the latest and best ABS software. Take away some of those factors and you will probably stop in the shortest distance using the ABS. Ideally you should apply the brakes slightly progressively, so you get the pads in contact with the discs and then transfer weight forwards onto the front wheels before you apply maximum braking. This is the way I remember Don Palmer teaching it.
On the Andy Walsh Car Limits DVD, he demonstrates that he can stop in a shorter distance using 'Threshold Braking' just before the ABS cuts in than using the ABS. But he achieves this in a car and on a surface he knows very well - and it is quite an old car which does not have the latest and best ABS software. Take away some of those factors and you will probably stop in the shortest distance using the ABS. Ideally you should apply the brakes slightly progressively, so you get the pads in contact with the discs and then transfer weight forwards onto the front wheels before you apply maximum braking. This is the way I remember Don Palmer teaching it.
My understanding is that even with the latest ABS you can brake in the dry faster by locking up or by being on the edge of locking, or indeed by cadence braking. What you can lose is the ability to steer. Even very good drivers will find it hard to judge how much brake you can apply whilst steering (after all its generally a bad idea). So if you need to steer use ABS, if you don't you will stop faster without it (albeit that it harm your tyres more if you do lock up)
In 1987 I had a Citroen BX19GTi with ABS. I soon found that it would trigger far too soon if the road was at all greasy or bumpy and on that car I reckoned I could stop quicker without it. On one country road covered in wet mud it took forever to slow sown.
However, that was then and modern ABS is much more sophisticated. Current systems monitor and brake each individual wheel at a far quicker rate than a driver could cadence brake. My understanding is that the advice now is that, in an emergency, you should brake as quickly and as hard as possible and let the ABS do its thing. For those of us brought up to avoid locking the wheels, this is counter intuitive, but that's progress!
However, that was then and modern ABS is much more sophisticated. Current systems monitor and brake each individual wheel at a far quicker rate than a driver could cadence brake. My understanding is that the advice now is that, in an emergency, you should brake as quickly and as hard as possible and let the ABS do its thing. For those of us brought up to avoid locking the wheels, this is counter intuitive, but that's progress!
Kermit power said:
EmmaP said:
Unless I've been misinformed, I thought 100% equalled maximum capacity.
In this case, 100% = the braking force needed to reach the very limit of traction but not break it, not the maximum possible braking force.
Force applied to the pedal? How is the limit of traction different from maximum braking in your car, have you got an air brake or something?
If you want to shed the most speed in the shortest time just stamp on the pedal & let the ABS do it for you. Depending on the car, road surface etc there may be subtle differences between whether you'll stop faster modulating just before the ABS kicks in or using it's assistance but if you're on a track the braking is less important than the exit from a corner so the difference is very minor, and on the road any circumstance where you need 100% stopping ability is going to be a surprise so you won't know the road surface well enough to know exactly where 100% is until you exceed it anyway.
hth.
Kermit power said:
In this case, 100% = the braking force needed to reach the very limit of traction but not break it, not the maximum possible braking force.
100% is always the maximum. Period. However, the percentage of potential force applied prior to loss of traction would be dependant on a number of variables. I'll stop being a pedant now
gdaybruce said:
In 1987 I had a Citroen BX19GTi with ABS. I soon found that it would trigger far too soon if the road was at all greasy or bumpy and on that car I reckoned I could stop quicker without it. On one country road covered in wet mud it took forever to slow sown.
However, that was then and modern ABS is much more sophisticated. Current systems monitor and brake each individual wheel at a far quicker rate than a driver could cadence brake. My understanding is that the advice now is that, in an emergency, you should brake as quickly and as hard as possible and let the ABS do its thing. For those of us brought up to avoid locking the wheels, this is counter intuitive, but that's progress!
However, that was then and modern ABS is much more sophisticated. Current systems monitor and brake each individual wheel at a far quicker rate than a driver could cadence brake. My understanding is that the advice now is that, in an emergency, you should brake as quickly and as hard as possible and let the ABS do its thing. For those of us brought up to avoid locking the wheels, this is counter intuitive, but that's progress!
I find that in the snow I can stop much quicker without ABS than with it in my 1997 Subaru Legacy (which does have proper 4-channel ABS). I think because the ABS applies, releases and reapplies the brakes so suddenly and quickly that it keeps locking the wheels when gentle gradual braking doesn't.
Similar thing with rough gravel too, ABS gets confused by the wheels momentarily locking as they skip over bumps and inconsistently loose stuff, whereas a wheel which is locked or nearly locked will bite through into the grippier stuff underneath.
Unless you go out and practice threshold or cadence braking a few times a month (which is almost nobody), then use ABS.
It's easy to overestimate how good you are at doing a non-ABS emergency stop. Even easier to overestimate your skill at brake-and-swerve. Both skills fade easily without practice.
Technology is there, so make use of it.
It's easy to overestimate how good you are at doing a non-ABS emergency stop. Even easier to overestimate your skill at brake-and-swerve. Both skills fade easily without practice.
Technology is there, so make use of it.
GravelBen said:
gdaybruce said:
In 1987 I had a Citroen BX19GTi with ABS. I soon found that it would trigger far too soon if the road was at all greasy or bumpy and on that car I reckoned I could stop quicker without it. On one country road covered in wet mud it took forever to slow sown.
However, that was then and modern ABS is much more sophisticated. Current systems monitor and brake each individual wheel at a far quicker rate than a driver could cadence brake. My understanding is that the advice now is that, in an emergency, you should brake as quickly and as hard as possible and let the ABS do its thing. For those of us brought up to avoid locking the wheels, this is counter intuitive, but that's progress!
However, that was then and modern ABS is much more sophisticated. Current systems monitor and brake each individual wheel at a far quicker rate than a driver could cadence brake. My understanding is that the advice now is that, in an emergency, you should brake as quickly and as hard as possible and let the ABS do its thing. For those of us brought up to avoid locking the wheels, this is counter intuitive, but that's progress!
I find that in the snow I can stop much quicker without ABS than with it in my 1997 Subaru Legacy (which does have proper 4-channel ABS). I think because the ABS applies, releases and reapplies the brakes so suddenly and quickly that it keeps locking the wheels when gentle gradual braking doesn't.
Similar thing with rough gravel too, ABS gets confused by the wheels momentarily locking as they skip over bumps and inconsistently loose stuff, whereas a wheel which is locked or nearly locked will bite through into the grippier stuff underneath.
You're right: snow and gravel are the only times when locking the wheels is a better option than keeping them rolling. That's why, on the original Quattros, there was a button to switch the ABS off.
What happens is that a locked wheel will build up a wedge of snow or gravel in front and this slows the car more effectively than if the wheel is turning. Incidently, I also had a 97 Legacy which was absolutley brilliant at keeping going in snow, but not so good at stopping, because of the ABS!
gdaybruce said:
GravelBen said:
gdaybruce said:
In 1987 I had a Citroen BX19GTi with ABS. I soon found that it would trigger far too soon if the road was at all greasy or bumpy and on that car I reckoned I could stop quicker without it. On one country road covered in wet mud it took forever to slow sown.
However, that was then and modern ABS is much more sophisticated. Current systems monitor and brake each individual wheel at a far quicker rate than a driver could cadence brake. My understanding is that the advice now is that, in an emergency, you should brake as quickly and as hard as possible and let the ABS do its thing. For those of us brought up to avoid locking the wheels, this is counter intuitive, but that's progress!
However, that was then and modern ABS is much more sophisticated. Current systems monitor and brake each individual wheel at a far quicker rate than a driver could cadence brake. My understanding is that the advice now is that, in an emergency, you should brake as quickly and as hard as possible and let the ABS do its thing. For those of us brought up to avoid locking the wheels, this is counter intuitive, but that's progress!
I find that in the snow I can stop much quicker without ABS than with it in my 1997 Subaru Legacy (which does have proper 4-channel ABS). I think because the ABS applies, releases and reapplies the brakes so suddenly and quickly that it keeps locking the wheels when gentle gradual braking doesn't.
Similar thing with rough gravel too, ABS gets confused by the wheels momentarily locking as they skip over bumps and inconsistently loose stuff, whereas a wheel which is locked or nearly locked will bite through into the grippier stuff underneath.
You're right: snow and gravel are the only times when locking the wheels is a better option than keeping them rolling. That's why, on the original Quattros, there was a button to switch the ABS off.
What happens is that a locked wheel will build up a wedge of snow or gravel in front and this slows the car more effectively than if the wheel is turning. Incidently, I also had a 97 Legacy which was absolutley brilliant at keeping going in snow, but not so good at stopping, because of the ABS!
A spin (on circuit, one hopes) represents another occasion when locking the wheels is advantageous, as it allows you to predict the direction that the car will take. I remember Porsche's 944 Turbo race car derivative had a brake system that allowed the driver to press "through" the ABS, to disengage it in the event of a spin. I also remember seeing an NSX spinning along the pit straight at Silverstone, until the rotating (ABS enabled)tyres gripped and fired the car into the pitwall...
WilliBetz
gdaybruce said:
...on the original Quattros, there was a button to switch the ABS off.
Really? I never knew that. Some of the quickest classic shape Imprezas (STi TypeR/RA) don't have ABS at all, but thats more because it gets confused by the lockable centre diff.
gdaybruce said:
What happens is that a locked wheel will build up a wedge of snow or gravel in front and this slows the car more effectively than if the wheel is turning.
Putting it sideways can also help scrub off speed more quickly on gravel as you then have 4 tyres using their sidewalls and tread to push wedges of gravel along, rather than 2 wheels pushing wedges with the tread and 2 following along their swept path. Might work in deepish snow too but doesn't seem to do much on thin stuff. I generally try to avoid using the brakes much in snow anyway though, prefer using weight transfer and that pedal on the right to keep it going where I want it to.Its very simple really:
If you want to stop with maximum effectiveness in an ABS car you should brake hard until the abs cuts in, then reduce brake pressure so the ABS only cuts in once every second or two rather than constantly going 'gnngnngnn'.
This method is the best compromise that will get you stopped quickest irrespective of unfamiliarity with the car and surface.
If you want to stop with maximum effectiveness in an ABS car you should brake hard until the abs cuts in, then reduce brake pressure so the ABS only cuts in once every second or two rather than constantly going 'gnngnngnn'.
This method is the best compromise that will get you stopped quickest irrespective of unfamiliarity with the car and surface.
MartinMGBGTSV8 said:
you should brake hard until the abs cuts in, then reduce brake pressure so the ABS only cuts in once every second or two rather than constantly going 'gnngnngnn'.
You seem to be suggesting that the maximum braking force is generated when the ABS is just barely coming in. And this may be true for all I know. But what makes you believe it is?
EmmaP said:
Kermit power said:
In this case, 100% = the braking force needed to reach the very limit of traction but not break it, not the maximum possible braking force.
100% is always the maximum. Period. However, the percentage of potential force applied prior to loss of traction would be dependant on a number of variables. I'll stop being a pedant now
GreenV8S said:
MartinMGBGTSV8 said:
you should brake hard until the abs cuts in, then reduce brake pressure so the ABS only cuts in once every second or two rather than constantly going 'gnngnngnn'.
You seem to be suggesting that the maximum braking force is generated when the ABS is just barely coming in. And this may be true for all I know. But what makes you believe it is?
Yes, I would also be interested to know. As far as I was aware, in an emergency braking situation the standard advice is to apply maximum pressure to the brake pedal and keep the pressure on, leaving the ABS to do its stuff.
Best wishes all,
Dave.
Edited by TripleS on Friday 20th April 09:32
TripleS said:
...A far as I was aware, in an emergency braking situation the standard advice is to apply maximum pressure to the brake pedal and keep the pressure on, leaving the ABS to do its stuff.
The standard advice is generally that given to all drivers regardless of ability though, so is the option likely to have the best effect for the largest number of morons. This is not necessarily the same as the way in which a more skilled driver could stop quickest though.
Also, ABS and/or stability control is tougher on the pads, discs, and calipers than threshold or cadence... vibration is never friendly to moving parts. so on track, that may be a factor. certainly wet sessions with DSC on in mine kill rear pads in short order.
I also agree that you need 5pc spare to deal with marbles, surface changes, missed gear, etc
The standard road-based answer to this is that ABS is there to allow steering, not to shorten stopping, and therefore improves brake-and-avoid.
Out of interest, was the OP talking about road or track?
I also agree that you need 5pc spare to deal with marbles, surface changes, missed gear, etc
The standard road-based answer to this is that ABS is there to allow steering, not to shorten stopping, and therefore improves brake-and-avoid.
Out of interest, was the OP talking about road or track?
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