[}{arlequin]

Originally Posted by TD in DC

The second benefit that you list is merely a byproduct of the first. The first benefit is really the only true benefit. Specifically, because ABS modulates braking force for you, you can steer without worrying about modulating the brakes. In reality, though, ABS does not take steering into consideration at all . . .

td, when you say "abs does nothing when you're travelling sideways" and then turn the phrase into "steering angle is not considered by abs sensors" i think it ends up confusing the issue. stop using extreme examples. well duh! when you travel sideways abs is useless. obviously. it also doesn't mean that it "doesn't work" when you're not pointed straight, it just means it doesn't work "as well", but it still does what it's supposed to- keep wheels from locking up.

and even though abs does not 'consider' your travel path nor slip angle on the tires, it does help (tremendously) in a midcorner application from spinning out the car. whether it's a by-product or not, it 'works' as in "it is effective" even if it's not in the ideal zero deviation from straight travel path of the vehicle... when you keep saying 'it doesn't work' i'm thinking 'it's not actuated' which isn't true.

sounds like we're all agreeing on the same thing but explaining/justifying it differently.

i know it helps the gen pop in driving when half the car is on slushy shoulder of the road and half on pavement so they don't lose control, but for me, (still and always), coming to an intersection w/ a speeding bus w/ a bomb on it heading for it, i'd rather stop sideways but w/in necessary distance, than stop in a straight line but be broadsided by the bus. how's that for extreme example?

[smdubovsky]

Originally Posted by }{arlequin

it does help (tremendously) in a midcorner application from spinning out the car.

}{, In a word- No. Thats not true. It does not change the physics of weight transfer at all. I've spun both the E30 and 996 at the track by braking (The 996 "situation" is on video somewhere and I'll be damned if I can figure out why it spun - but I digress.)

In the extreme examples of split traction, it can help, but thats not the majority of panic stop situations. ABS simply keeps you from locking the brakes. The main objective is shorter stopping. The side benefit (as TD pointed out), that since the wheels aren't locked, they can still steer. BTW, all of this is still doable w/o ABS.

FWIW, The E30 abs makes steering and braking WORSE. If I hit my braking mark, and get the ABS to kick in due to a bump (or just too much peddle), the car is going deep (and thus off). I have to cycle the peddle to get the braking back under control. Both at the chute and oak tree turns, if the ABS kicks in while trail braking, you can also kiss you line goodby. The front end goes from biting nicely to terminal understeer. Doesnt happen w/ the ABS off (but you will chirp/lift/lock the inside rear). The 996 & boxster don't extend braking - it works much better. I can't comment on their steering affect as I haven't trail braked either of them as wantonly. The boxster has PSM which does other stuff. That REALLY works to keep the car from spinning and is the solution the government is proposing.

SMD
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Harmed by zoloft

[TD in DC]

Originally Posted by smdubovsky

ABS simply keeps you from locking the brakes. The main objective is shorter stopping. The side benefit (as TD pointed out), that since the wheels aren't locked, they can still steer. BTW, all of this is still doable w/o ABS.

Thanks. That is all I meant.

[}{arlequin]

Originally Posted by smdubovsky

}{, In a word- No. Thats not true. It does not change the physics of weight transfer at all. I've spun both the E30 and 996 at the track by braking (The 996 "situation" is on video somewhere and I'll be damned if I can figure out why it spun - but I digress.)

In the extreme examples of split traction, it can help, but thats not the majority of panic stop situations. ABS simply keeps you from locking the brakes. The main objective is shorter stopping. The side benefit (as TD pointed out), that since the wheels aren't locked, they can still steer. BTW, all of this is still doable w/o ABS.

this is obviously not working through the keyboard for me.... i didn't mean to suggest that abs changes weight transfer of the car, merely that the fact that its real act, of not locking up wheels, has kept many a car still heading in the desired direction.

where i get this from?- had a 528 rental on a ski vacation. the long curvy descent through roads w/ varying conditions had abs kicking in frequently. could i have done the drive w/o abs? of course, but the average driver doesn't consider such aspects and would lose control of the car. if it was me, i'd have to lift, regain grip/steering and continue.... w/ the abs, i didn't have to lift. just do nothing and continue on down the hill.

even though the intended purpose is to shorten panic stops, i think the real application of not locking up wheels has helped many drivers in situations *other* than panic stops. meaning, abs for those people, was effective at times when they were not traveling straight.

as for track usage, i'm sure the older system on the e30 is a hindrance and can easily see how it screws up and makes you understeer. this goes along w/ my "stop straight but far enough to get hit by the bus" example... i used to turn it off completely in my prior track car.

[TD in DC]

Originally Posted by }{arlequin

even though the intended purpose is to shorten panic stops, i think the real application of not locking up wheels has helped many drivers in situations *other* than panic stops. meaning, abs for those people, was effective at times when they were not traveling straight.

ABS doesn't care what your purpose is. It is merely a stupid mechanical system designed to modulate braking when the wheel stops rotating. That's it. So, whenever the wheel stops rotating, ABS will activate. Keeping the wheel rotating helps you whether you are engaging in a straight line panic stop or trying to steer, or just trying to burn off speed. ABS doesn't care about your intent. It just cares that the wheel isn't turning anymore.

P.S. I don't see how ABS would be bad under any circumstance. I am not saying that it isn't, but I am just admitting that I don't get it. If ABS activates, it means that you would have locked up the tire in its absence. You can still modulate manually, so why would you need to turn it off.

[smdubovsky]

}{, I'd vote the average driver doens't know to swerve so the steering side-benefit of ABS isn't as usefull. Most accidents are full on rear ends. All THREE of the people who have rear ended me didn't think to swerve. Sort of a deer in the headlights / target fixation thing.

Originally Posted by TD in DC

P.S. I don't see how ABS would be bad under any circumstance.

Drive an ABS car in snow. To us who used to live where we'd get FEET of snow every year, driving an ABS car in the stuff induces some panic. My old toyota corolla (RWD) and the girlfriends 66 VW where champs in the snow. (though the corolla required a full tank of gas) My old Jeep XJ sucked in the snow w/ its wider tires, but its 4wd would allow you to just stay on the gas though the turn... even though the rear tires were in the ditch outside said turn

Also, I've done donuts/powerslides in the E30 here at work. I got overzealous ONE time, ran out of steering lock, and went two feet in. The car instead of going straight in the direction I was travelling, hooked towards the curb since I couldn't lock'em up. I didn't hit it, but caught lots of flak from my friend who was right behind me (he was laughing his ass off). When I spun the 996 the ABS also very nearly looped me into a wall (instead of spinning safely straight.) Its hard to reteach your brain on why the car wont go the direction its supposed to. The 996 ABS was FANTASTIC at Roebling in the pouring rain though (for stopping in a straight line).

SMD
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BLACK AMATEUR

[TD in DC]

Originally Posted by smdubovsky

}{, I'd vote the average driver doens't know to swerve so the steering side-benefit of ABS isn't as usefull. Most accidents are full on rear ends. All THREE of the people who have rear ended me didn't think to swerve. Sort of a deer in the headlights / target fixation thing.



Drive an ABS car in snow. To us who used to live where we'd get FEET of snow every year, driving an ABS car in the stuff induces some panic. My old toyota corolla (RWD) and the girlfriends 66 VW where champs in the snow. (though the corolla required a full tank of gas) My old Jeep XJ sucked in the snow w/ its wider tires, but its 4wd would allow you to just stay on the gas though the turn... even though the rear tires were in the ditch outside said turn

Also, I've done donuts/powerslides in the E30 here at work. I got overzealous ONE time, ran out of steering lock, and went two feet in. The car instead of going straight in the direction I was travelling, hooked towards the curb since I couldn't lock'em up. I didn't hit it, but caught lots of flak from my friend who was right behind me (he was laughing his ass off). When I spun the 996 the ABS also very nearly looped me into a wall (instead of spinning safely straight.) Its hard to reteach your brain on why the car wont go the direction you want it to. The 996 ABS was FANTASTIC at Roebling in the pouring rain though (for stopping in a straight line).

SMD

I grew up driving in a lot of snow . . . and I still don't understand . . . honestly. When the ABS starts to chatter, why can't you just modulate your braking force exactly like you would do in a non ABS situation. The "only" difference I can see is that you would lose the ability to stop by "piling" up snow and debris in front of your tires (creating your own chock by pushing the lose stuff). So, I guess I can see how ABS might make stopping distances longer in really loose sloppy stuff, but how would it have any impact on direction of travel? Honest question.

[}{arlequin]

Originally Posted by TD in DC

I grew up driving in a lot of snow . . . and I still don't understand . . . honestly.

yes but did you drive then w/ the same mentality you have now? eye on usage/performance etc ...since the answer is no i'm betting you weren't aware of what you were missing from the 'evaluation'

i've felt the system continue doing its thing even after i lifted off the pedal... i think what's happening is that once you 'tell it' to take over, it will continue to take over until all the readings on its sensors come w/in specified parameters, ie: speed, attitude, steering angle, weight load etc etc... wheras w/o that 'help' you could lock up, throw the car into a slide and stop in a straight line while sliding in the predicted direction. w/ abs running, the wheels don't lock ever, so you continue to roll even though you simply wished the wheels to stop rolling so you could slide in the desired direction instead of rolling in the undesired direction

[racer]

Originally Posted by TD in DC

ABS doesn't care what your purpose is. It is merely a stupid mechanical system designed to modulate braking when the wheel stops rotating. That's it.

Which begs the question, how does a car with ABS know that you actually want to come to a complete stop and not just keep you moving?