The disadvantages of ABS
05-21-2003, 11:40 PM
#16
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I asked this same question to David Murry at track event. I was running my US Carrera Cup and was told that ABS was a down fall.
David said one thing I'll never forget and it has saved my car more than once in a race. "You can still steer the car with ABS".
Say what you want to about the physics and the idea of both feet during a spin, but two years ago racing in a HSR event at Sebring, in a 934, I went into turn 17 too fast, I locked up the brakes and hit the wall.
This past year at Sebring's PCA race, during qualifying, I did the same thing in my Cup car. I hit the ABS, steered away from the wall and later cleaned out my drvers suit.
Years ago many pro drivers had no choice but to drive a car without ABS. They learned to be able to modulate the brakes. I bet given the chance to have ABS or not today, most of them would take it. The pro drivers I know, have said just that!
David said one thing I'll never forget and it has saved my car more than once in a race. "You can still steer the car with ABS".
Say what you want to about the physics and the idea of both feet during a spin, but two years ago racing in a HSR event at Sebring, in a 934, I went into turn 17 too fast, I locked up the brakes and hit the wall.
This past year at Sebring's PCA race, during qualifying, I did the same thing in my Cup car. I hit the ABS, steered away from the wall and later cleaned out my drvers suit.
Years ago many pro drivers had no choice but to drive a car without ABS. They learned to be able to modulate the brakes. I bet given the chance to have ABS or not today, most of them would take it. The pro drivers I know, have said just that!
05-21-2003, 11:51 PM
#17
Three Wheelin'
Stuttgart,
You nailed it! I wouldn't trade my Supercup's brakes w/racing ABS for anything. Simply phenomenal! <img border="0" title="" alt="[Eek!]" src="eek.gif" />
You nailed it! I wouldn't trade my Supercup's brakes w/racing ABS for anything. Simply phenomenal! <img border="0" title="" alt="[Eek!]" src="eek.gif" />
05-22-2003, 10:57 AM
#18
Race Director
People like Vic Elford, Hurley Haywood, Jackie Stewart say they can better brake with a non-ABS equipped car: they have the sensitivity in their feet to be able to modulate the brake pedal with better modulation than any conventional ABS system, race-designed or not. And they probably can!
Club racers, DE participants (me!) and autocrossers (me again!) probably don't have the experience or sensitivity to be able to brake "better" than an ABS system allows you to.
ABS is a fantastic saftey net for me! I've just moved up into the "wild white" run group in my PCA region's DE program (intermediate level). So now, I'm gaining confidence in my driving, and as such, I'm braking later, harder into the corners. Occasionally, I'll over-cook it a little. At that point, ABS will allow me to do two things at once: still brake & turn in sharply. It's not the trail braking that I'm speaking of here: it's over cooking a corner and trying to slow down as much as possible even during the initial turn in. Without ABS, I'd be either spinning, or taking said corner much faster than I THINK I can take it. With ABS, I can stil be HARD on the brakes, and have a little steering control.
Aside from bumpy parts of the track, street derrived ABS systems still are great on the track.
Erick: I think the scenario you describe occurs more when someone goes off track, and then turns sharply to get back on track. Not anticipating the sudden gain in traction, the car hooks up and launches over to the other side. I do not think ABS would give one that much more traction if the car never left the track to begin with.
Just my $0.42
-Z.
Club racers, DE participants (me!) and autocrossers (me again!) probably don't have the experience or sensitivity to be able to brake "better" than an ABS system allows you to.
ABS is a fantastic saftey net for me! I've just moved up into the "wild white" run group in my PCA region's DE program (intermediate level). So now, I'm gaining confidence in my driving, and as such, I'm braking later, harder into the corners. Occasionally, I'll over-cook it a little. At that point, ABS will allow me to do two things at once: still brake & turn in sharply. It's not the trail braking that I'm speaking of here: it's over cooking a corner and trying to slow down as much as possible even during the initial turn in. Without ABS, I'd be either spinning, or taking said corner much faster than I THINK I can take it. With ABS, I can stil be HARD on the brakes, and have a little steering control.
Aside from bumpy parts of the track, street derrived ABS systems still are great on the track.
Erick: I think the scenario you describe occurs more when someone goes off track, and then turns sharply to get back on track. Not anticipating the sudden gain in traction, the car hooks up and launches over to the other side. I do not think ABS would give one that much more traction if the car never left the track to begin with.
Just my $0.42
-Z.
05-22-2003, 11:09 AM
#19
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I had a Rothmans Turbo 944 Cup. This series was one of the first that the driver had a ABS on/off switch. At the first of the series, the drivers hated the ABS and would keep the switch off. Later in the series everyone was using the ABS and the drivers for the series told reporters, the ABS braking was far superior in this series than not having it.
I have to believe that only a professional driver would have the experience to make a sensable reply on this thread.
We have to rely on what we have experienced in our own situations. I personally like having it and agree with an earlier post. Based on my experience, I feel my ABS Cup brakes are superior and I can drive deeper into a corner than a non ABS car. I can slow the car down by utilizing the ABS and turn the car at the same time. You can't do that when your wheels are locked.
I have to believe that only a professional driver would have the experience to make a sensable reply on this thread.
We have to rely on what we have experienced in our own situations. I personally like having it and agree with an earlier post. Based on my experience, I feel my ABS Cup brakes are superior and I can drive deeper into a corner than a non ABS car. I can slow the car down by utilizing the ABS and turn the car at the same time. You can't do that when your wheels are locked.
05-22-2003, 11:16 AM
#20
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Vic, Hurley, and Jackie are blowing smoke up your A$$ and don't know enough about ABS to be qualified to speak. Sounds like some of the crowd here know more than they do! And I do mean that as a compliment. Danno made the good point about algorithm, software levels, and even hardware levels - they've come a long way! Some mention loss of decel while braking over bumps. The old Chevy S10 is notorious for this. Old algorithm, can't deal with it. Things are much more advanced now. Likewise, compare the 3-channel wheel-speed-based ABS on a 951 with the 4-channel slip-based controller in the PSM ABS (which is what I work on). I'd count on the PSM level of ABS (Bosch ESP 5.3 or 5.7 IIRC) to just blow the doors off the old ABS 5.0 in the 951. You have the additional advantages of optimizing the braking force on every wheel, which cannot be done in a non-ABS car no matter how good your driver is, I don't care if he's Michael Freakin Schumacher. The old 3-channel system is still working through a prop valve on the rear, and cannot control the rears independently. A modern 4-channel system like PSM, or even the equivalent level ABS-only system, working without a prop valve, will be much better.
As an added advantage, the control with a PSM-based system is so much smoother, it will upset the dynamics of the car far less - kinda like taking to the track with a set of Penske's vs. a set of Bilsteins, I'd say. You can slam on the brakes and the car will just stand on it's nose, no pitching moment like normal ABS.
The point has been made - you can still steer with ABS. It's up to you, the driver, to make sure you're steering in an appropriate direction!! The car will do whatever you tell it to, so make sure you make an appropriate request!
FWIW, some Audi's had ABS-off switches...
As an added advantage, the control with a PSM-based system is so much smoother, it will upset the dynamics of the car far less - kinda like taking to the track with a set of Penske's vs. a set of Bilsteins, I'd say. You can slam on the brakes and the car will just stand on it's nose, no pitching moment like normal ABS.
The point has been made - you can still steer with ABS. It's up to you, the driver, to make sure you're steering in an appropriate direction!! The car will do whatever you tell it to, so make sure you make an appropriate request!
FWIW, some Audi's had ABS-off switches...
05-22-2003, 12:05 PM
#21
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One data point I can add to Bryan's earlier speculation: The acknowledged ability of abs to increase your late braking options in a corner has not prevented my discovering that, at least on my quattro S2 early-gen ABS, ABS does indeed work in reverse.
Interesting trivia: these late '80's early '90's Audis all had a nice big abs on/off switch on the dash. I always kept abs on when I tracked the car.
Brandon H
quattro S2
911SC G-car
Interesting trivia: these late '80's early '90's Audis all had a nice big abs on/off switch on the dash. I always kept abs on when I tracked the car.
Brandon H
quattro S2
911SC G-car
05-22-2003, 02:31 PM
#22
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Post all the algorithms you want to. Talk about slide rules and scientific equations. Bottom Line: That all flys out the window if you the driver doesn't know how how to drive.
I know from experience these guys that you are saying are blowing smoke up my @5$#, are more qualified and experienced than you an I are.
I wonder 924rcr, have you ever raced against any of these guys? Have you ever been the co-driver in your own car, when one of these guys have taken it to a farther limit than you can? We are talking PSM, just ABS.
I know from experience these guys that you are saying are blowing smoke up my @5$#, are more qualified and experienced than you an I are.
I wonder 924rcr, have you ever raced against any of these guys? Have you ever been the co-driver in your own car, when one of these guys have taken it to a farther limit than you can? We are talking PSM, just ABS.
05-22-2003, 03:02 PM
#24
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Greg Fishman:
<strong>I am just impressed that a Chevy S-10 made it into this conversation. That has to be a first!</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">I can tie this in a bit better. A '95 Chevrolet Astro cargo van, aka 'the gearbox kart hauler' (obligatory racing content) has the most **** poor ABS system known to man. The ABS will engage over moderate bumps on dry pavement and not disengage till your foot is removed the from the pedal. When the ABS engages, it feels like the vehicle is on ice! I wouldn't be surprised if this ABS system has caused quite a few accidents.
<strong>I am just impressed that a Chevy S-10 made it into this conversation. That has to be a first!</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">I can tie this in a bit better. A '95 Chevrolet Astro cargo van, aka 'the gearbox kart hauler' (obligatory racing content) has the most **** poor ABS system known to man. The ABS will engage over moderate bumps on dry pavement and not disengage till your foot is removed the from the pedal. When the ABS engages, it feels like the vehicle is on ice! I wouldn't be surprised if this ABS system has caused quite a few accidents.
05-22-2003, 03:13 PM
#25
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Shhh, Steve, you'll start another lawsuit! <img border="0" title="" alt="[Wink]" src="wink.gif" />
Jim, I don't need to. I know the algorithms inside and out - that's what I do for a living, for Bosch. We have a cute little ad running in the trade magazines, an under-dash picture showing 4 brake pedals... kinda gets the point across. Your last sentence was typoed, but I presume you meant to say "we're NOT talking PSM here, just ABS." The comparison is only made WRT ABS, not PSM/ESP. A microprocessor operating on a 20ms loop time is far more capable than any human brain born of simultaneously modulating the pressure in four different control circuits to the limit of adhesion. To say otherwise is challenging the laws of physics. I do race, and I test cars on a regular basis at the test track. I for one don't plan on challenging the laws of physics.
Again, keep in mind here the discussion is ABS only, not the ability of the driver to maximize use of traction available at all times. I never said I could beat Jackie or the like around a track - only that my ABS tuning could beat them into a corner.
Before idolizing the racing greats, consider some of the lovely quotes attributed to the late, great, Carroll Smith...
Talk amongst yourselves.
Jim, I don't need to. I know the algorithms inside and out - that's what I do for a living, for Bosch. We have a cute little ad running in the trade magazines, an under-dash picture showing 4 brake pedals... kinda gets the point across. Your last sentence was typoed, but I presume you meant to say "we're NOT talking PSM here, just ABS." The comparison is only made WRT ABS, not PSM/ESP. A microprocessor operating on a 20ms loop time is far more capable than any human brain born of simultaneously modulating the pressure in four different control circuits to the limit of adhesion. To say otherwise is challenging the laws of physics. I do race, and I test cars on a regular basis at the test track. I for one don't plan on challenging the laws of physics.
Again, keep in mind here the discussion is ABS only, not the ability of the driver to maximize use of traction available at all times. I never said I could beat Jackie or the like around a track - only that my ABS tuning could beat them into a corner.
Before idolizing the racing greats, consider some of the lovely quotes attributed to the late, great, Carroll Smith...
Talk amongst yourselves.
05-22-2003, 03:20 PM
#26
Burning Brakes
My impression was that all pro Carrera Cup/Supercup drivers (964/993/GT3) used the ABS at all times unless they are in an emergency in which case the punch button mounted very close to their hand is used to disable the ABS. This emergency would be going on gravel or going backwards.
05-22-2003, 09:55 PM
#27
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This is getting a bit out of hand....
anyway the part number for the Carrera cup USA edition ABS defeat swtich/harness is 964.612.003.75. this switch hooks up to the existing S C2 harness (the US edition used the standard C2 harness). i have no idea if this harness is advailable at the parts counter (prob not) and if it will work with a non-motorsports ABS system.
My 2 cents - if you are tring to modulate an ABS to the point of lock up you are waisting your time, the system cycles faster than a human. while not fool proof it allows you to steer out of trouble. The ABS defeat switch is intended for off track excursions (wet grass,etc) where locked wheels will stop you faster, hopefully!
anyway the part number for the Carrera cup USA edition ABS defeat swtich/harness is 964.612.003.75. this switch hooks up to the existing S C2 harness (the US edition used the standard C2 harness). i have no idea if this harness is advailable at the parts counter (prob not) and if it will work with a non-motorsports ABS system.
My 2 cents - if you are tring to modulate an ABS to the point of lock up you are waisting your time, the system cycles faster than a human. while not fool proof it allows you to steer out of trouble. The ABS defeat switch is intended for off track excursions (wet grass,etc) where locked wheels will stop you faster, hopefully!
05-23-2003, 09:30 AM
#28
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WRT shutting the system off... following comments apply to "normal" (street-only) ABS... you've got a couple of options. A number of 951 drivers need to cycle power to the unit after setting a fault (wheel speed sensor fault) on track after running across gators' teeth. For this purpose, when you only want to briefly disable the system, I recommend use of a normally-closed (on), momentary-off (open) pushbutton switch. Naturally this gets wired into the power lead of the ABS ECU (which is usually pin #1, but YMMV). This way you can just tap the switch briefly to cut power only momentarily, then power is restore and the unit resets without any additional effort from the driver. Minimal distraction. I see a lot of this done with a standard pushbutton switch, which requires 2 movements from the driver, and so provides more distraction.
Of course, the latter type of switch would be more appropriate if you're looking to turn it off and leave it off for the aforementioned reasons, in gravel. I'd be rather surprised, based on my experiences driving sideways with ABS on and off, to find that it made a big difference, particularly in the negative direction, in spin recovery. More typically you'll just lose the reference (vehicle speed) calculation as the car gets totally sideways and, as mentioned, the wheels don't recover (spin up), so you'll just end up w/ locked wheels anyway.
Of course, the latter type of switch would be more appropriate if you're looking to turn it off and leave it off for the aforementioned reasons, in gravel. I'd be rather surprised, based on my experiences driving sideways with ABS on and off, to find that it made a big difference, particularly in the negative direction, in spin recovery. More typically you'll just lose the reference (vehicle speed) calculation as the car gets totally sideways and, as mentioned, the wheels don't recover (spin up), so you'll just end up w/ locked wheels anyway.
05-23-2003, 10:18 AM
#30
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Hm. About the only relevant experience I've got is threshold braking to stay just OUT of the ABS. I've read that *straight-line*, dry surface braking distances are longer w. ABS than without. Perhaps this is just the older systems? At any rate, my heavy braking is all in a straight line, with some light trail braking at the end. When I'm heavy on the brakes in a straight line, I'm able to flutter just on the edge of ABS. I *think* this is the right thing to do for maximum deceleration; am I wrong here?