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  Jan. 13, 2011 7:19 a.m. Streetwiseguy HalfDork

  AngryCorvair wrote:

  Streetwiseguy, (1) he wasn't on glare ice, (2) he still had his foot on the brake, and (3) he was on a downhill grade. As far as the Astro = Deathtrap comment, perhaps you could cite some reputable numbers linking Astro ABS performance to crashes? And a question for you: How do you "use up all your ABS capacity"?

  I don't have reputable numbers. I have, however, driven Astro vans with 4 wheel abs. They are terrifying. Glare ice conditions, they will not stop in a reasonable distance without engaging neutral or turning the key off. If you would care to join me in the frozen north, I think I can get my habds on one, and we can do some testing.

  As to the using up comment, that was a bit random.

  I also am frightened regularly by my 2k Silverado, which hates potholes. I don't mind the antilock as such, but it pushes back on the pedal so hard the braking to the other wheels is compromised. I'm a big guy, and I can't push the pedal hard enough to get things slowed down until the abs has quit actuating.

  In my experience, GM has the most over-intrusive abs and traction control in the industry.

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  Jan. 13, 2011 12:38 p.m. AngryCorvair SuperDork

  Streetwiseguy wrote:

  Glare ice conditions, they will not stop in a reasonable distance without engaging neutral or turning the key off. If you would care to join me in the frozen north...

  Sounds like an issue with ineffective rear brakes or poor system balance, but not something that can be blamed solely on the ABS.

  I also am frightened regularly by my 2k Silverado, which hates potholes. I don't mind the antilock as such, but it pushes back on the pedal so hard the braking to the other wheels is compromised. I'm a big guy, and I can't push the pedal hard enough to get things slowed down until the abs has quit actuating.

  short answer is that ABS controls fronts individually, and rears either individually (on cars and some light trucks) or together (some light trucks). When ABS dumps pressure to one circuit in response to speed signal from the sensor on that circuit indicating that the tire(s) on that circuit are approaching lockup, it must also prohibits pressure buildup on that circuit for the duration of the dumping event plus some stabilization time after that dumping event as it waits to see the wheel speed on that circuit come back to normal.

  So, during the dump and hold event, you can not increase pressure on that circuit no matter how hard you push on the pedal.

  The "pushing back on the pedal" is from the pump moving dumped fluid from the holding area inside the unit, through a check valve, to the portion of that hydraulic circuit between the MC and the ABS unit. It absolutely 100% in no way affects the pressure available to the other circuits. Certainly, overall vehicle deceleration is affected, but so is vehicle stability and vehicle steerability.

  If you're going a speed that requires 80 ft to stop at max decel, and something (a kid on a bike, a car backing out of a driveway, etc) pops out 50 feet in front of you, do you want max decel or are you willing to trade some decel for some steerability?

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  Jan. 13, 2011 1:12 p.m. Streetwiseguy HalfDork

  AngryCorvair wrote:

  Streetwiseguy wrote:

  Glare ice conditions, they will not stop in a reasonable distance without engaging neutral or turning the key off. If you would care to join me in the frozen north...

  Sounds like an issue with ineffective rear brakes or poor system balance, but not something that can be blamed solely on the ABS.

  I also am frightened regularly by my 2k Silverado, which hates potholes. I don't mind the antilock as such, but it pushes back on the pedal so hard the braking to the other wheels is compromised. I'm a big guy, and I can't push the pedal hard enough to get things slowed down until the abs has quit actuating.

  short answer is that ABS controls fronts individually, and rears either individually (on cars and some light trucks) or together (some light trucks). When ABS dumps pressure to one circuit in response to speed signal from the sensor on that circuit indicating that the tire(s) on that circuit are approaching lockup, it must also prohibits pressure buildup on that circuit for the duration of the dumping event plus some stabilization time after that dumping event as it waits to see the wheel speed on that circuit come back to normal.

  So, during the dump and hold event, you can not increase pressure on that circuit no matter how hard you push on the pedal.

  The "pushing back on the pedal" is from the pump moving dumped fluid from the holding area inside the unit, through a check valve, to the portion of that hydraulic circuit between the MC and the ABS unit. It absolutely 100% in no way affects the pressure available to the other circuits. Certainly, overall vehicle deceleration is affected, but so is vehicle stability and vehicle steerability.

  If you're going a speed that requires 80 ft to stop at max decel, and something (a kid on a bike, a car backing out of a driveway, etc) pops out 50 feet in front of you, do you want max decel or are you willing to trade some decel for some steerability?

  I want the vehicle to do what I request of it. I'm sure there are lots of good arguments about maintaining steering control while not stopping when you were supposed to, but most of the half wits that would help probably have taken their hands off the wheel to cover their eyes while screaming to their death.

  My last statement on the situation is this- Over- intrusive ABS scares the E36 M3 out of me.

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  Jan. 13, 2011 1:44 p.m. Brett_Murphy Reader

  In reply to MrJoshua:

  Preach on, brother.

  What I'd like to see is tunable ABS, since it would be nice to have more options besides "off" and "What the engineers decided to use".

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  Jan. 13, 2011 2:07 p.m. AngryCorvair SuperDork

  kb58 wrote:

  Good points! As I recall, some "real" cars (ws it Porsche?) have a disable button for the ABS

  i am unaware of any abs-equipped vehicle ever designed for sale in North America that ever came equipped with an ABS Disable button. ever.

  did i mention ever?

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  Jan. 13, 2011 2:59 p.m. MrJoshua SuperDork

  AngryCorvair wrote:

  kb58 wrote:

  Good points! As I recall, some "real" cars (ws it Porsche?) have a disable button for the ABS

  i am unaware of any abs-equipped vehicle ever designed for sale in North America that ever came equipped with an ABS Disable button. ever.

  did i mention ever?

  Sure they did-they just hid it in the fuse box disguised as a fuse.

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  Jan. 13, 2011 4:23 p.m. 4cylndrfury SuperDork

  Brett_Murphy wrote:

  What I'd like to see is tunable ABS, since it would be nice to have more options besides "off" and "What the engineers decided to use".

  +a whole lot

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