Why some ABS brakes work flawlessly others don't ?

[supton]

Well, the truck suffers from little weight in the rear, so even with snow tires it may well be still tail-happy. The other two cars, no details so can't tell.

30mph may have been too fast for you also, and you were just lucky.

If you see lots of ice in your area, it may be worthwhile to get studded tires. Or tires with great ratings for ice, I have not read up on the studless snows but tire tech seems to keep moving forward. In my area we see more fluffy stuff than ice, and not that much, so I have not paid as much attention as I ought.

 

[JHZR2]

So much of this is in weight distribution and tires. Maybe some conrtrol systems are a little "antsy", but overall even my 23 year old systems seem to work well.

 

[Quest]

IMO ABS systems work effectively only if the following conditions apply:

(1) all 4 tires are not overly worn and/or hardened
(2) all 4 shocks/struts are in good functional order
(3) all 4 corners: the braking hardware (for calipers, the slider pins are not binding/seized; for drum type ABS: the auto adjustment mechanism is functioning properly (not seized,bind) so as be able to maintain proper brake shoe to drum clearances, drum braking mechanism is functioning properly with no seizure nor binding.
(4) no brake system leaks, air, or issues on the hydraulic system.

Most of the partial ABS issues I came across has more or less to do with these 4 points. When all 4 of these are in good working order, your ABS system should be able to keep the vehicle in fairly straight line during ABS-assisted braking.

Q.

 

[Petersubaru]

Originally Posted By: supton
Well, the truck suffers from little weight in the rear, so even with snow tires it may well be still tail-happy. The other two cars, no details so can't tell.

30mph may have been too fast for you also, and you were just lucky.

If you see lots of ice in your area, it may be worthwhile to get studded tires. Or tires with great ratings for ice, I have not read up on the studless snows but tire tech seems to keep moving forward. In my area we see more fluffy stuff than ice, and not that much, so I have not paid as much attention as I ought.
…I don't think I was possibly just lucky…never a problem with the subi, and same goes for my 1986 jetta..pulling on the parking brake is the only way to cause a spin for that car...

 

[morris]

it all comes down to the fact the car makers make a car ONLY GOOD ENOUGH.

 

[eljefino]

Originally Posted By: RF Overlord
Originally Posted By: Tegger
depending on the driver's skill, and on moral hazard.

on icy roads, where danger is the greatest, traction the least, and moral hazard your worst enemy.
What exactly is a "moral hazard"? I'm familiar with drinking, gambling, and cheating on your wife, but never heard it applied to a driving condition.


A moral hazard is shielding someone from consequences even though you previously declared you wouldn't.

Example, bailing out the banks who frittered away their money back in the crisis.

The moral hazard here is assuring drivers that no matter how dumb they are they can stand on the pedal and everything will be all right.

A coworker had a late model dodge (avenger?) with traction control and "hi fly" all season tires that would sit there at 1500 RPM in drive with the pedal to the floor, not moving in the snow.

 

[turtlevette]

ABS is not stability control and won't correct a operator induced slide. That said, it should allow the vehicle to brake straight in most situations.

Stability control has several accelerometers that detect motion of the vehicle front to back and side to side and apply the brakes individually and unequally to correct a slide. On some cars there is a normal mode and sport mode which decides how aggressive the computer is going to be. The guys writing the code determine how it is going to perform. Some have more experience than others. The sports car guys probably have the better experience. I believe the Corvette people were some of the first to do this and have more experience with it.

 

[Tegger]

Originally Posted By: 440Magnum
nowhere does it say that the computer does anything with the steering rack. It implies "steering" the vehicle, but not in the sense of turning the wheel anywhere other than where the driver turns it.

This is a quote from the page I referenced:
"...if the steering wheel refuses to turn from over-speeding
(under-steering), the vehicle will take control to steer toward
the inner curve. Also, when the vehicle begins to spin from
abrupt steering handling (over-steering), the vehicle will
take control to steer toward the outer curve."

I don't know how else to interpret "vehicle will take control to steer" other than that the computer will manipulate the power steering system so as to force the steering wheel into the direction it wants the wheel to go.

 

[Tegger]

Originally Posted By: eljefino
A moral hazard is shielding someone from consequences even though you previously declared you wouldn't.

"Moral hazard" is the unintended consequences of shielding -- or appearing to shield -- someone from the consequences of his actions. Previous declarations are not part of the concept.

When people feel protected when performing a given action, they take less care in what they do. This means that protection can actually increase harm. For example: Concussions were almost unheard of in the NHL before helmets were mandated. Now hardly a month goes by when they don't talk about the serious problem of concussions.

 

[440Magnum]

Originally Posted By: Tegger
Originally Posted By: 440Magnum
nowhere does it say that the computer does anything with the steering rack. It implies "steering" the vehicle, but not in the sense of turning the wheel anywhere other than where the driver turns it.

This is a quote from the page I referenced:
"...if the steering wheel refuses to turn from over-speeding
(under-steering), the vehicle will take control to steer toward
the inner curve. Also, when the vehicle begins to spin from
abrupt steering handling (over-steering), the vehicle will
take control to steer toward the outer curve."

I don't know how else to interpret "vehicle will take control to steer" other than that the computer will manipulate the power steering system so as to force the steering wheel into the direction it wants the wheel to go.


The problem is, its written in Engrish, not English.

It doesn't make ANY sense the way its actually written. Why would the "steering wheel refuse to turn" for any reason? What happens is the wheel turns due to driver input and the vehicle may refuse to turn due to understeer or turn too much due to oversteer. When that happens, the stability system uses BRAKES to try to correct. But it can only do that if grip exists.

It does NOT turn the steering wheel, trust me on that one. The most sophisticated systems may manipulate the power assist to encourage the driver in a particular way or to shake the wheel as a warning, but that's the limit of it.

 

[hattaresguy]

Originally Posted By: 440Magnum
Originally Posted By: Tegger
Originally Posted By: Rand
What cars does it turn the steering wheel for you?

Maybe all of them.

http://www.toyota-global.com/innovation/...active/vsc.html



That system uses brakes, just like all of them. Read it CAREFULLY- nowhere does it say that the computer does anything with the steering rack. It implies "steering" the vehicle, but not in the sense of turning the wheel anywhere other than where the driver turns it. I don't think any of them do, or ever will because the steering wheel is the only thing that tells the stability algorithm what the driver is trying to actually DO with the car. The computer senses the rate of rotation of the car, compares it to which way the driver is pointing the steering wheel, and does everything it can with the brakes to get the car to go where the driver is pointing it. The minute the computer takes over moving the wheel, car is driving itself, blind to the driver's input, and any stability algorithm without added external inputs (lane sensors, obstacle sensors, etc.) fails. What is still TOTALLY incumbent on the driver is anticipating what's going to happen. The driver cant just throw the best stability control system in the world into a hairpin turn at 80 mph in the snow and expect to come out the other side with the shiny side up.

It would be different if the car could sense the lane boundaries... but even then what if the driver is swerving out of the lane to avoid a kid in the road? Eventually we'll get to self-driving cars that can detect the lane AND the kid, but for the most part we're not there yet.




The new E and S class Mercedes are nearly self driving.

Still people stuff them in the ditch which I think is rather challenging. Morons really.

I remember last winter a poor driver almost took me out with their brand new IS Lexus which has all kinds of traction aids. They were simply going to fast.

Modern cars are very good though, they really cut down on accidents.



Look ma no hands!

Modern cars are like modern fighter jets, the computers do things no human could possible do. While this car is driving its not only reading the lines, but it has night vision and infrared for night driving and is always looking 360 degrees around the car. It also knows what the speed limits are on every road.

 

[440Magnum]

Originally Posted By: hattaresguy




Look ma no hands!

Modern cars are like modern fighter jets, the computers do things no human could possible do. While this car is driving its not only reading the lines, but it has night vision and infrared for night driving and is always looking 360 degrees around the car. It also knows what the speed limits are on every road.


If drivers went through the same training as fighter jet pilots so that they were competent to a) not exceed the abilities of the driving aids, and b) be competent enough to recover quickly if the aids fail, then that might be a good idea. As it is, I think its just one more thing to turn drivers into semi-involved passengers rather than being DRIVERS first and foremost.