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'[EE]:: ABS increases stopping distance by typicall'
2008\01\26@020857 by Apptech

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A competent authority has assessed that ABS brakes INCREASE stopping
distances on gravel (metal) surfaces by typically 20+ percent.

       en.wikipedia.org/wiki/Anti-lock_braking_system
A 2003 Australian study[2] by Monash University Accident Research Centre
found that ABS:

 a.. Reduced the risk of multiple vehicle crashes by 18 percent.
 b.. Reduced the risk of run-off-road crashes by 35 percent.
On high-traction surfaces such as bitumen, or concrete many (though not all)
ABS-equipped cars are able to attain braking distances better (i.e. shorter)
than those that would be easily possible without the benefit of ABS. Even an
alert, skilled driver without ABS would find it difficult, even through the
use of techniques like threshold braking, to match or improve on the
performance of a typical driver with an ABS-equipped vehicle, in realworld
conditions. ABS reduces chances of crashing, and/or the severity of impact.
The recommended technique for non-expert drivers in an ABS-equipped car, in
a typical full-braking emergency, is to press the brake pedal as firmly as
possible and, where appropriate, to steer around obstructions. In such
situations, ABS will significantly reduce the chances of a skid and
subsequent loss of control.

In gravel and deep snow, ABS tends to increase braking distances.

On these surfaces, locked wheels dig in and stop the vehicle more quickly.

ABS prevents this from occurring.

Some ABS calibrations reduce this problem by slowing the cycling time, thus
letting the wheels repeatedly briefly lock and unlock. The primary benefit
of ABS on such surfaces is to increase the ability of the driver to maintain
control of the car rather than go into a skid — though loss of control
remains more likely on soft surfaces like gravel or slippery surfaces like
snow or ice. On a very slippery surface such as sheet ice or gravel it is
possible to lock multiple wheels at once, and this can defeat ABS (which
relies on detecting individual wheels skidding). Availability of ABS
relieves most drivers from learning threshold braking.

But part of the answer is that on heavy snow, locked wheels can be useful
because they gather up a "wedge" of snow which helps to slow the vehicle.
ABS allows this wedge to clear every time the wheels are unlocked. The same
can apply on sand in some conditions.

A June 1999 NHTSA study found that ABS increased stopping distances on loose
gravel by an average of 22 percent [1].



_________



Very interesting paper on ABS brake accident stats.

No great relationship to gravel roads.





2008\01\26@032631 by William \Chops\ Westfield

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On Jan 25, 2008, at 11:08 PM, Apptech wrote:

> A competent authority has assessed that ABS brakes INCREASE stopping
> distances on gravel (metal) surfaces by typically 20+ percent.

Is that a surprise?  I thought the point of ABS was to increase
CONTROL (steering) during heavy breaking, not so much to decrease
stopping distance.  In fact, I'm surprised that ABS *ever* decreases
stopping distance...

BillW

2008\01\26@073814 by Apptech

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>> A competent authority has assessed that ABS brakes
>> INCREASE stopping
>> distances on gravel (metal) surfaces by typically 20+
>> percent.

> Is that a surprise?

No.
I wrote that mainly for my son, who has recently purchased a
car with ABS and was telling me how well it stopped on
gravel.

> I thought the point of ABS was to increase
> CONTROL (steering) during heavy breaking, not so much to
> decrease
> stopping distance.

Yes & No.
ABS generally decreases stopping distances and that is a
major aim, as is increased control.

Optimum stopping typically occurs when the tyres are
slipping at about 10 - 15% of their rolling speed. More than
that and skid onset is imminent. Less than that and you
could get more stopping. A really really really competent
driver may be able to hold a vehicle in this region. Joe
average hasn't a show. ABS allows you to do this with ease
and concentrate on steering and avasion and ... .

> In fact, I'm surprised that ABS *ever* decreases
> stopping distance...

As above.

I've read that cars with ABS rates have a higher percentage
of solo male fatalities than cars without. That makes sense
:-) - but the reasons may not be what they first seem. eg it
could be that males who drive by themselves are more likelt
to buy cars with ABS brakes.


       Russell


2008\01\26@084723 by Carl Denk

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In the USA, you don't have a choice with ABS brakes, except with older
vehicles, and I agree, that a more skillful driver could reduce the
stopping distance, but it is nice to have that available, just wish I
could turn it off at times. But it appears to me that many times the
braking force available isn't as much as it could be. Many vehicles on
good friction dry pavement cannot with hard pedal pressure lock the
wheels sufficiently to bring the ABS into action. All that happen is
that you come to a longer than necessary stop.

The traction control, which is an add-on to the ABS is very nice, in
particular when one wheel has traction and the other does not, but
accelerating out of a tight corner, I frequently turn it off since
slight wheel slippage at full throttle can result in cutting power to
the fuel injectors.

Part of the real issue though is driver training. Today driving under
adverse conditions including defensive and playing the game with a
future vision, of eyes all over the place i.e. a mile ahead, the merging
traffic, etc. is not taught.

Apptech wrote:
{Quote hidden}

2008\01\26@090049 by Carl Denk

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Sure decreases stopping distance in certain conditions, take a sheet of
ice, compare just standing on the brakes with and without ABS on a
straight stop, or with one side wheels good traction. A skillful (how
many of those do you know) driver may be able to better the numbers.  
And yes the ABS is great on turns, but not the answer.Was just the other
day with 2002 Cougar, front wheel drive, big engine, ABS and traction
control, was making tight (maybe 50' radius) turn at low speed on ice.
Was at no throttle, tranny in drive, front start sliding, a little
throttle ans front sliding friction turned to static friction, and turn
completed on planned track. Neither ABS or traction control helped
there. To add enough throttle for those to become active, and the
remainder of the turn would have been too fast for anything to help.



William "Chops" Westfield wrote:
{Quote hidden}

2008\01\26@092227 by Funny NYPD

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this is not surprise at all. GM canceled the ABS as a standard equipment on all its America models couple of years ago, because  of the poor performance and constant issue it created.
GM claimed the user still can buy it as a option, but GM does't take any responsibility if anything happened. It is the user responsibility to put the ABS on the vehicle.
Hard to understand, isn't it?
Funny N.
New Bedford, MA
http://www.AuElectronics.selfip.com



{Original Message removed}

2008\01\26@094710 by Carl Denk

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Funny things happen, I ordered a 1989 Ford Bronco (full size 4WD SUV)
with the manual locking front hubs as standard equipment. Then there was
a Chevy ad on the TV showing the Ford driver getting out in the middle
of a water filled creek bed to lock the hubs, where Chevy had the
automatic locking hubs. When the Bronco got delivered 2 weeks later, the
automatic hubs were standard, and the manual were a $41 deduct. For
those not familiar, the locking hubs engage the front drive axles to the
front wheels. With the hubs unlocked, fuel economy is 3 MPG or more
better, which is around 25%. The disadvantage of the automatic hubs are:
don't know if they are engaged or not; if get stuck and have to rock to
get out, they can be ruined easily since they lock/unlock with each
change of direction; Much more expensive to repair ($250 for parts vs.
$50). Most experienced 4 wheelers prefer the manual hub, but there are
some variations out there including air  pressure/vacuum or electric
operated.

I'm amazed at the number of drivers out there who spend the money for
4WD/FWD/All wheel drive, and don't know how to use, or even use it when
it's slippery. On the other hand, daughter has a Ford Freestyle FWD
minivan. I stopped at the Ford dealer to understand how the system
worked so I could help her use it best. Sales didn't know, went with me
to parts and service. We learned nothing. The unit is serviced as a
unit, the parts book only had a picture of the unit, no gears, bearings,
etc. The technician (mechanic) who had been to the service school didn't
know anything more.

Funny NYPD wrote:
> this is not surprise at all. GM canceled the ABS as a standard equipment on all its America models couple of years ago, because  of the poor performance and constant issue it created.
> GM claimed the user still can buy it as a option, but GM does't take any responsibility if anything happened. It is the user responsibility to put the ABS on the vehicle.
> Hard to understand, isn't it?
> Funny N.
> New Bedford, MA
> http://www.AuElectronics.selfip.com
>
>
>
> {Original Message removed}

2008\01\26@101155 by Apptech

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> And yes the ABS is great on turns, but not the answer.Was
> just the other
> day with 2002 Cougar, front wheel drive, big engine, ABS
> and traction
> control,

A man here has a Lamborghini for sale on the local auction
site.
Then it turned up in multiple photos in the main city paper,
and disappeared from auction site.

In the paper it was notched beautifully onto a power pole
with bits of Lambo strewn far and wide
As may be seen here.

       http://zoltuger.orcon.net.nz/lambo/gotcha/-post

An "explanation" of how a presumably competent driver can
wrap a $NZ450,000 car around a suburban power pole is given
here

       http://zoltuger.orcon.net.nz/lambo/newspaper.jpg

They say that the traction control was off and that a rear
wheel skid as the car turned right was picked up by the
computer sending power to the front wheels as the driver
corrected by turning to the left, as one does. Needless to
say, anyone who attempts to drift a Lamborghini through a
city T intersection under significant power really should
know his (her) car and does really deserve the outcome if
they haven't done their homework.

They quote Michael Schumaker on traction control in
supercars. "If you have the skills of a Formula One driver,
turn it off. If you don't, don't."
_____________

My ye olde Mk1 Supercharged MR2 has none of these things.
There is a local corner - right hand, off camber, BIG bump
in the middle, around a wee traffic island, gutter protrudes
into apex. I used to delight in throwing lesser cars into
this corner at the legal speed limit (50 kph). Kabump
kathump hop skitter,  crabs sideways claws for traction
maybe drifts a bit under under steers, throttle on, here
comes the curb, cmon bite now or, ah - kathump, turns right
and claws its way up the street past the island.
I had to give it up with the MR2 - it just goes round the
corner, shakes its head a bity and proceeds up the hill. To
make it exciting I'd have to throw it into the corner at far
far far greater speeds. I try to not exceed speed limits -
not always successfully. So paradoxically, in the MR2 I
instead go around that corner slower :-). The MR2, though
traction controlless, will take "open road" bends at 2x
posted speed with ease and 3x with suitable care. So
anything posted at 50 kph+ is suitable for legal open road
100 kph speeds and at 30 kph + posted you can do it while
making life interesting. You can take ANY right angle corner
at 50 kph and stay on the correct side of the road (with
good tyres on) if you are willing to believe it is possible.
Doubt tends to set in occasionally. A fun car.







       Russell


2008\01\26@103710 by Carl Denk

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That 89 Bronco, nothing like an adrenalin rush with 5.8L HO (high
output) at full throttle in low range at 50 MPH, hitting a 5 foot high
snow drift, snow flying everywhere. Better have the driver's side window
rolled down and watching the side of the road, because a lot of that
snow is going to end up on the hood (bonnet) in front of the windshield.:)

Apptech wrote:
{Quote hidden}

2008\01\26@114015 by McReynolds, Alan A

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Indeed it is true on gravel, sand, and other loose material.  In my experience loose gravel stopping distances are more like 2x not +20%.  That experience is mostly on dry desert gravel and sand.

An off-road vehicle should have a manual or automatic means of disabling the ABS system.  For example, locking any of the differentials on my truck automatically turns off the ABS.

...Alan

{Original Message removed}

2008\01\26@123045 by Carl Denk

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The 1996 Bronco with manual hubs and transfer case (part time), the ABS
cannot be turned off. The vehicle has limited slip differentials both
front and rear that are the spring loaded multiple friction disc
variety. With everything locked up, stops on slippery, the ABS does
kicking in occasionally, but not near as frequently when 4wd not locked
up. The limited slip does pretty much keeps things turning at the same
rate. With slightly different depth tire treads side/side on the front,
with the hubs locked, it will pull to one side. When rotating tires for
the winter, need to pay attention to that. On tight corners on dry,
locked up, slow speed, sometimes can feel tires slipping, kind of like a
hop, probably part due to the non-constant velocity cross/yoke U-joints.
On very slippery tight corner, locked up, might go straight, where the
forward component overpowers the side component with steering hard to
one side. On other hand very stable straight ahead on sheet of ice, can
cruise on ice at 65 mph with no concern for staying on straight road, as
long as don't have to stop the 5300+ pounds fast.

McReynolds, Alan A wrote:
> Indeed it is true on gravel, sand, and other loose material.  In my experience loose gravel stopping distances are more like 2x not +20%.  That experience is mostly on dry desert gravel and sand.
>
> An off-road vehicle should have a manual or automatic means of disabling the ABS system.  For example, locking any of the differentials on my truck automatically turns off the ABS.
>
> ...Alan
>
> {Original Message removed}

2008\01\26@140907 by Gerhard Fiedler

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Funny NYPD wrote:

> this is not surprise at all. GM canceled the ABS as a standard equipment
> on all its America models couple of years ago, because  of the poor
> performance and constant issue it created.

ABS may not be (and probably isn't) ABS. This seems to be a rather tricky
control feature, and I'm sure there are big differences between different
ABS manufacturers.

Gerhard

2008\01\26@142432 by Carl Denk

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I don't know but I alway thought ABS = Anti-lock brake system, where the
relative motion of each wheel/axle was sensed, analyzed, and if a wheel
had significant less speed than the remaining (other?) wheels, it's
brake was applied, and without getting into a lot more detail. And yes
there are many different systems and how they react out there. Generally
there is a sensor at each wheel consisting of a slotted rotating disc,
and a hall effect sensor. The 1996 Bronco, and that's early in the ABS
evolution has sensors on each front wheel, but only one on the rear
differential ring gear. Now we a getting into the turf of knowing your
vehicle and how it functions.

Gerhard Fiedler wrote:
{Quote hidden}

2008\01\26@190206 by Matt Pobursky

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On Sat, 26 Jan 2008 17:08:27 -0200, Gerhard Fiedler wrote:
> Funny NYPD wrote:
>
>> this is not surprise at all. GM canceled the ABS as a standard
>> equipment on all its America models couple of years ago, because  of
>> the poor performance and constant issue it created.
>>
>
> ABS may not be (and probably isn't) ABS. This seems to be a rather tricky
> control feature, and I'm sure there are big differences between different
> ABS manufacturers.
>
> Gerhard

Ding, Ding, Ding! We have a winner!

One of my major clients makes ABS systems for trucks and for the past
several years I've been designing test and diagnostic equipment for them as
well as some aftermarket add-ons. I'm not an ABS expert by any means but I
have observed a lot of test data can tell you that the level of what passes
for ABS hugely varies between the automotive companies.

GM makes the most "brain dead" ABS system on the market for use with their
"mainstream" models. It uses the cheapest and fewest wheel sensors,
relatively crude brake modulators and the simplest braking algorithm. The
reason they pulled ABS as standard was two-fold: 1) Cost and 2) It only
worked well if you just hammered the brake pedal to the floor and kept it
there (letting the ABS system totally control the braking). They had a lot
of problems with drivers pumping the brakes (as they were taught to do),
which caused the ABS system to modulate braking on top of the user
modulating it... very bad. There were accidents (and legal actions) caused
by this so it's no wonder GM no longer supplies it as standard equipment.
On the other hand, I've heard the ABS systems on Cadillacs and Corvettes
are quite excellent. Amazing, huh?

The ABS systems you see from BMW, Mercedes, Acura, Lexus are much more
sophisticated and generally tied in with the other traction and throttle
control functions. Toyota and Honda are somewhere in the middle and the
rest of the U.S. manufacturers bring up the rear. Generally, the more
quality and engineering oriented auto companies have the best ABS systems
(big surprise, huh?).

Truck ABS systems are quite a bit more interesting as the better ones
integrate things like anti-rollover algorithms where they take
accelerometer data into account along with wheel speed to sense trailer
sway and wheel lift and apply braking that counteracts the trailer motion.
You should see them test these systems, it's very cool! I asked one of the
test drivers how many trailers he's rolled over and his answer was "too
many to count". :-)

Matt Pobursky
Maximum Performance Systems

2008\01\26@194051 by Jake Anderson

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>
> GM makes the most "brain dead" ABS system on the market for use with their
> "mainstream" models. It uses the cheapest and fewest wheel sensors,
> relatively crude brake modulators and the simplest braking algorithm. The
> reason they pulled ABS as standard was two-fold: 1) Cost and 2) It only
> worked well if you just hammered the brake pedal to the floor and kept it
> there (letting the ABS system totally control the braking). They had a lot
> of problems with drivers pumping the brakes (as they were taught to do),
> which caused the ABS system to modulate braking on top of the user
> modulating it... very bad. There were accidents (and legal actions) caused
> by this so it's no wonder GM no longer supplies it as standard equipment.
> On the other hand, I've heard the ABS systems on Cadillacs and Corvettes
> are quite excellent. Amazing, huh?
>  
I was under the impression that "pumping" the brake pedal was always a
bad idea. If you don't have ABS and you can't threshold brake (which is
most likely) you lock it up unless/until you need to steer. Just
randomly pumping it sounds like it will just extend your stopping
distance and given all those shocks of going into and out of a skid it
seems like there would be a larger chance of getting sideways.

I guess it all boils down to knowing your vehicle. When you buy an
airplane you get "checked out" on it as a rule and this is for people
who know their stuff. Perhaps a similar idea would be a good thing for
cars. You buy it then the dealer/certified person takes you for a 20
minute drive with some emergency stops and cornering in it. As well as
telling you how to turn your fog lights off when there is no actual fog.

2008\01\26@195339 by Carl Denk

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I worked for 3 years at Bendix Truck R&D headquarters (I worked in the
facilities management area for the building and equipment). My turf took
me to everyone and the facility there. There is a powerhouse of
mechanical and electrical engineers working on the products which
included ABS and disc brakes for heavy highway vehicles. They run there
own fleet of various including some not so common vehicles for full
scale testing, and every winter send a considerable crew to Northern
Michigan for ice and old weather testing.  The facilities include
numerous  thermal test chambers and a brake dyno with a huge flywheel.
It's exciting to see a full scale test as Semi sized tires are subject
to a high speed test as the brakes are applied. Also there was a regular
string of fleet equipment in and out for actual useage testing.

Matt Pobursky wrote:
{Quote hidden}

2008\01\26@214515 by Funny NYPD

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Bendix ABS is designed in Germany by another "small" company. The Bendix traditional-Technology ABS works like a charm, but not the new digital network ones with J1939 network.

It's J1939 protocol design is very bad. Almost every time, when there is any issue on a new J1939 network for a new Motor Home/Trucks product, Bendix is the trouble maker.

And the real issue is: Bendix never fix those issues.
So, don't be surprise if you found it is not working right on your new Coach or Trucks.

Funny N.
New Bedford, MA
http://www.AuElectronics.selfip.com



{Original Message removed}

2008\01\27@015526 by Dumitru Stama

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ABS generally enlarges braking distance, it's a fact. You can disable it
by pulling out the fuse from the fusebox. Especially in the winter time
where having ABS is almost a suicide in our country it is a really good
ideea to render it unusable because without ABS you have a greater
chance of stopping the car when in need.
The system is implemented differently in various types of cars, i own
a suzuky jimny (or Sierra in USA) and the ABS kicks in very very
late in the process of braking. It also has a very bold engine brake
\which helps a lot in the city traffic.
On the other hand on my other car which is a honda accord (or Acura
TSX in USA) the ABS system kicks in quickly. When i break in
emergency situations i tend to keep the foot down on the pedal.
With my old car (a peugeot) i already had two minor accidents (bumps)
because of ABS. I guess it depends from driver to driver but for me is
better to keep ABS OFF because i encountered more situations when
it didn't help then the ones when it helped.

2008\01\28@055141 by Alan B. Pearce

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>Truck ABS systems are quite a bit more interesting as the better
>ones integrate things like anti-rollover algorithms where they take
>accelerometer data into account along with wheel speed to sense
>trailer sway and wheel lift and apply braking that counteracts the
>trailer motion. You should see them test these systems, it's very
>cool! I asked one of the test drivers how many trailers he's rolled
>over and his answer was "too many to count". :-)

Sounds like a fun job ... ;))

2008\01\28@073356 by Michael Rigby-Jones

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> -----Original Message-----
> From: spam_OUTpiclist-bouncesTakeThisOuTspammit.edu [.....piclist-bouncesKILLspamspam@spam@mit.edu] On
Behalf
> Of Matt Pobursky
> Sent: 27 January 2008 00:02
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE]:: ABS increases stopping distance by typically 20%+
> ongravel surfaces
>
>
> Truck ABS systems are quite a bit more interesting as the better ones
> integrate things like anti-rollover algorithms where they take
> accelerometer data into account along with wheel speed to sense
trailer
> sway and wheel lift and apply braking that counteracts the trailer
motion.
> You should see them test these systems, it's very cool! I asked one of
the
> test drivers how many trailers he's rolled over and his answer was
"too
> many to count". :-)

That sounds more like a stability control system than simple ABS, e.g.
similar to BMWs DSC system.

The one big advantage that the better anti-lock systems have over a
skilled driver is that the modulator has control over individual wheels,
so it can resolve a single locked wheel without affecting the rest of
the wheels.  Cadence braking releases pressure from all wheels,
decreasing the amount of valuable braking work they can achieve.

On loose surfaces optimum braking is often achieved by locking the
wheels and allowing the loose surface to pile up in front of the tyres,
so ABS often loses in these situations.  Another problem with some ABS
is on some rough road surfaces where the tyre can leave the road
intermittently which causes the ABS to activate far too quickly, and
gives a "driving on ice" feeling.

Regards

Mike

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2008\01\28@112732 by Eoin Ross

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My old Discovery has a "centre diff lock" that locks up the transfer case diff - otherwise its permanent 4WD, it only binds up like yours when that is locked. Same issues in a Suzuki Samurai, Subaru Leone/DL, Suzuki XL7 - anything that locks front/rear drive together.

It's due to the front and rear driveshafts turning at the same speed, even though the front needs to go faster. The hops come from the driveline forces building up and overcoming the tyre/ground forces, relieving the pressure in a "hop", then building up again. Much like earthquakes from a faultline.

>>> cdenkspamKILLspamalltel.net 26 Jan 08 12:30:41 >>>
The 1996 Bronco with manual hubs and transfer case (part time),
<snip>
On tight corners on dry, locked up, slow speed, sometimes can feel tires slipping, kind of like a
hop, probably part due to the non-constant velocity cross/yoke U-joints.
<snip>


2008\01\28@122255 by Carl Denk

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I believe why the Bronco is so stable on ice in a straight line is, the
front turns at a slightly greater speed than the rear axles. The front
an rear differentials are the same ratios, the transfer case has a
timing chain that has slightly different number of teeth on the main
drive, and the front drive. This is good gear and chain design practice
so the chain "hunts", doesn't always mesh the same teeth, but every
revolution is over a tooth or 2. Yea, the terms part-time and full-time
four wheel drive are really misnomers. The Bronco is considered
part-time, the transfer case full disconnects the front driveshaft from
the tranny, and hard connects when in engaged, no fluid, slip clutches
or differentials. The better gas mileage results when both the transfer
case and front hubs are disengaged and the front differential gears are
not turning. I'm amazed at the number of Dodge pickups I follow, and am
able to see the front U-joints turning, even on bright sunny days, a
vehicle that looks like it never will get near the mud. :)

Eoin Ross wrote:
{Quote hidden}

2008\01\28@130612 by Martin

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Carl Denk wrote:
> In the USA, you don't have a choice with ABS brakes, except with older
> vehicles, and I agree, that a more skillful driver could reduce the
> stopping distance, but it is nice to have that available, just wish I
> could turn it off at times. But it appears to me that many times the
> braking force available isn't as much as it could be. Many vehicles on
> good friction dry pavement cannot with hard pedal pressure lock the
> wheels sufficiently to bring the ABS into action. All that happen is
> that you come to a longer than necessary stop.
> ...
Pull the fuse or disconnect the ABS box. You're in for a bad time if you
do this and get in an accident (lawyers).
>
> Part of the real issue though is driver training. Today driving under
> adverse conditions including defensive and playing the game with a
> future vision, of eyes all over the place i.e. a mile ahead, the merging
> traffic, etc. is not taught.
>
>  



Take a motorcycle safety course then. They teach highly defensive
driving skills.
-
Martin

2008\01\28@152121 by Carl Denk

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One of the things done is increase the normal (perpendicular) force to
the fiction surfaces (disc caliper) by either increasing the caliper
piston area, or the effective area of the vacuum power booster. I have
had on my back burner, on the 96 Bronco (think Ford F150 pickup), is to
change out the calipers to 2 piston version from I think it's a full
size sedan, maybe police interceptor Ford, the master cylinder bore
size, and the power brake booster from a 1 diaphragm to a smaller dia. 2
diaphragm from and F-250. There is info available, but, just haven't had
time to take vehicle out of service for a few weeks to  find and fit the
right pieces. And yes it has to be a concentrated effort to match all
the sizes, diameters to have a good working system.

As for pulling the fuse, unless I'm missing something, the ABS is not
active until  there is differential rotation of a wheel, and then will
loosen the brake on the offending wheel. If the ABS is not active, then
it's straight hydraulic pressure from the master cylinder to the wheel
pistons, force on the master cylinder amplified by the vacuum booster.
Since unable to lock up or even slid any wheel, the ABS has no effect
and pulling the fuse won't help.

Martin wrote:
{Quote hidden}

2008\01\29@134037 by Herbert Graf

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On Mon, 2008-01-28 at 13:05 -0500, Martin wrote:
> Carl Denk wrote:
> > In the USA, you don't have a choice with ABS brakes, except with older
> > vehicles, and I agree, that a more skillful driver could reduce the
> > stopping distance, but it is nice to have that available, just wish I
> > could turn it off at times. But it appears to me that many times the
> > braking force available isn't as much as it could be. Many vehicles on
> > good friction dry pavement cannot with hard pedal pressure lock the
> > wheels sufficiently to bring the ABS into action. All that happen is
> > that you come to a longer than necessary stop.
> > ...
> Pull the fuse or disconnect the ABS box. You're in for a bad time if you
> do this and get in an accident (lawyers).

ABS is becoming more and more integrated with other systems. It is
common in many cars for the same fuse feeding the ABS module to feed
other systems, so pulling the fuse has become less and less an option.

The fact is ABS is a compromise, while it adversely affects car
performance in some situations, for most people for the conditions they
are in it is a good thing.

Personally I find ABS to be complete junk in real winter driving
(stopping distances are FAR longer, by a large margin), but that's for
someone who grew up driving in winter conditions.

TTYL

2008\01\29@134321 by Herbert Graf

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On Mon, 2008-01-28 at 15:21 -0500, Carl Denk wrote:
> As for pulling the fuse, unless I'm missing something, the ABS is not
> active until  there is differential rotation of a wheel, and then will
> loosen the brake on the offending wheel. If the ABS is not active, then
> it's straight hydraulic pressure from the master cylinder to the wheel
> pistons, force on the master cylinder amplified by the vacuum booster.
> Since unable to lock up or even slid any wheel, the ABS has no effect
> and pulling the fuse won't help.

I once had an 88 olds that on dry pavement could NOT lock the wheels
with full brake force. I looked in the manual and basically they said
that was for safety reasons since a car with spinning wheels is more
controllable!

ABS was an option on that car, I wonder if the ABS version of the car
had stronger brakes?

TTYL

2008\01\31@142841 by Dumitru Stama

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> As for pulling the fuse, unless I'm missing something, the ABS is not
> active until  there is differential rotation of a wheel, and then will
> loosen the brake on the offending wheel. If the ABS is not active, then
> it's straight hydraulic pressure from the master cylinder to the wheel
> pistons, force on the master cylinder amplified by the vacuum booster.
> Since unable to lock up or even slid any wheel, the ABS has no effect
> and pulling the fuse won't help.

What do you mean ? If ABS is non-functional then you will have a classic
braking system on your hands (or under your foot). Pulling out the fuse
will deactivate ABS system and your wheels will lock under hard breaking.
If the fuse controls something else besides ABS then it may be a little harder
to choose the "pull out" option

2008\01\31@154142 by Carl Denk

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What I said, was the power assisted brakes do not have sufficient
hydraulic pressure > clamping force to the front calipers to skid the
wheels on dry good friction pavement with modern tire tread material. If
a wheel doesn't slide, then the ABS is not entering the picture. Yes
this is the non-abs situation. I did check the electrical diagrams, and
there is a wire going to the powertrain (engine & transmission)
controller. Have no idea what that's doing, didn't get into the
troubleshooting area of the manual.

Dumitru Stama wrote:
{Quote hidden}

2008\01\31@163633 by Herbert Graf

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On Thu, 2008-01-31 at 21:28 +0200, Dumitru Stama wrote:

> What do you mean ? If ABS is non-functional then you will have a classic
> braking system on your hands (or under your foot). Pulling out the fuse
> will deactivate ABS system and your wheels will lock under hard breaking.
> If the fuse controls something else besides ABS then it may be a little harder
> to choose the "pull out" option

The op was speaking of a car that CAN'T lock it's wheels under full
braking on dry pavement. Those cars are out there, I had one! :)

TTYL

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