Anti-Lock Brakes

<div class='quotetop'>QUOTE(GeronimoPFudgemuffin @ Nov 22 2006, 09:24 PM) [snapback]353392[/snapback]</div>

You are both right and wrong . . . depending on the road conditions.

I believe these sources will qualify as the epitome of credibility . . .

Do car antilocks reduce crashes?
Although car antilocks perform well on the test track, there is no evidence they have made significant reductions in the number of on-the-road crashes.
http://www.iihs.org/research/qanda/antilock.html
</span>
Better brakes are in our future:
<span style="color:#009900">eBraking cuts stopping distance 50%
http://www.autoblog.com/2006/11/10/ebrakin...ng-distance-50/

 

<div class='quotetop'>QUOTE(priusenvy @ Nov 27 2006, 03:48 AM) [snapback]354382[/snapback]</div>

Actually, I think you're wrong, mainly because you're trying to take an absolute position. In the real world, many factors are involved. To say that ABS will absolutely always provide shorter stopping distance under any possible scenario on dry pavement is wrong. Other factors include car weight and suspension, tire width, pavement type and cleanliness. For example, I suspect a low 2,500 lb sporty car with 9 inch wide tires going 5 mph would stop faster by locking up the brakes. Stopping might be instantaneous, or close to it. Any hestitation due to ABS cycling would lengthen stopping distance.

I agree ABS brakes are better overall. But based on my experience, ABS lengthens stopping distance during emergency stops at slow speed when there is no room or time to drive around obstructions. I've done some racing and much aggressive driving in my youth. I've done rapid stops in non-ABS cars many times and know how quickly cars can stop. A few months ago, I had to slam on the Prius brakes when doing about 15 mph. In this particular situation, I could tell the stopping distance was lengthened by failure to lock up the wheels.

 

<div class='quotetop'>QUOTE(nyprius @ Nov 28 2006, 10:54 PM) [snapback]355140[/snapback]</div>

You're not understanding the point I was trying to make. Please try to follow. There are two separate arguments here:

1) For a tire on pavement, is the static or sliding coefficient of friction higher?

2) Does ABS provide shorter stopping distances?

Those are two separate questions, and the answer to the first does not dictate the answer to the second. I did not try to answer the second question.

You stated that the sliding coefficient of friction for a tire on pavement is higher than the static coeff. of friction. It isn't, and you were wrong. That answers the first question. That says nothing about the answer to the second question.

 

<div class='quotetop'>QUOTE(priusenvy @ Nov 29 2006, 03:40 AM) [snapback]355145[/snapback]</div>

I was referring to stopping distance, not coefficent of drag. I'm not an engineer and don't know what that means. My point from the start was that my experience indicates ABS lengthens stopping distance on some dry pavement conditions, such as low speeds.

 

Without question I want ABS, VSC, and a “real†Traction Control on any modern vehicle I drive. Toyota has had to juggle the regenerative braking and ABS, and it’s fairly easy to upset it if you’re gradually braking on pavement, then hit a momentary slippery section, such as a manhole cover.

On gravel I’d have to state that ABS does produce longer stopping distances. My hobby farm is at the end of a 4.5km gravel sideroad, and my 1984 Ford F-150 can stop much quicker with all four wheels locked, then my Prius can with ABS engaged. This is the only situation I can think of, I wouldn’t want an empty pickup truck on icy roads.

Oh, if Toyota is listening, your “traction control†is a joke. Why not do what the Europeans do, and actually apply a brake to a spinning wheel? I’ve had one wheel on ice and one wheel on dry pavement, and my Prius has been helpless without winter tires.

 

well posting here to say that i am completely astounded and impressed with my Prius. i specifically upgraded to skid control in conjunction with traction control and i cant believe how well they worked on near glare ice.

we have had very bad weather here and while cruising the South Sound area yesterday (put over 150 miles on it, did all my x-mas shopping and met my Dad who lives in Texas for lunch as well) the roads were simply put... a joke. over 40 abandoned vehicles from grid-lock clearing over 180 accidents in the area from Monday night. reports of people taking 8 hours to drive home from the Seahawk game Monday night...etc...its really bad (we simply aint used to this stuff i guess!!)

but while driving in downtown Tacoma, came down this one steep hill with obvious icy conditions, (it was sanded but not thawed) the road was relatively clear, so i locked up the wheels and at the same time changed lanes. even while sliding down the hill, i had total control of the car. i'm pretty sure that i would have slid completely thru the intersection i was at in a regular car but as it was, i stopped nearly a half block short. when changing lanes, the rear did not swing around as i expected it to do, it was a smooth transition from one lane to the other.

MAN I LOVE MY PRIUS!!

 

<div class='quotetop'>QUOTE(Curtis SAC @ Nov 27 2006, 03:36 AM) [snapback]354385[/snapback]</div>

Don't take this as an affront, but tell me: HOW would ABS accomplish the above? I may be missing something, but I don't see how this could be.

I'm trying to nail-down (in my mind) what ABS can and cannot do, and how it does it. That's what the thread is about, so I'm using it as a springboard to thought and discourse, not a hammer meant for the first mole that sticks-up his head. (ever play that arcade game? that's what these forums often turn into)

Of course, I'm not talking about what ABS could do, but rather, what it actually does, at present. Some future implimentation of ABS might be "smarter" than the current flavors, just as the current is surely smarter than the early versions. So, my question mainly concerns what ABS does now.

Future versions might use engine torque to turn the wheels against the load. This, in cooperation with stability control, could stop REALLY quickly and accurately... but they don't do it now.

GeronimoPFudgemuffin

 

<div class='quotetop'>QUOTE(priusenvy @ Nov 29 2006, 12:40 AM) [snapback]355145[/snapback]</div>

static coefficient will always be much higher... iow, greater traction, less skidding likely, etc.

ABS if working properly, yes will stop shorter simply because its very nature of actuating the brakes several times a second makes it stay in static friction mode which provides the most opposition to forward kinetic motion

if in doubt check the sliding block on an inclined plane experiment. a wooden block is set on a board and the board is tipped paying attention the to angle of the board when the block starts to slide. this figure approximates the static co-efficient.

then take the same block move it to angle and tap it with your finger. eventually you will get to an angle where the block will slide to the bottom after the tap. that is the "sliding" co-efficient

either way, i think the control issues far out weigh any minor differences in stopping distances

 

<div class='quotetop'>QUOTE(Sufferin' Prius Envy @ Nov 27 2006, 06:16 AM) [snapback]354389[/snapback]</div>

Thank you for taking the time to look-up these sources.

I should add that I read every one of the offered links... and more. I'm not against ABS and I DO "believe" the links. But I also should add that, the last time I read about it, early ABS cars were represented in MORE crashes (based on percentage so-fitted) than non-ABS cars. But that was early ABS, and the ones doing the complaining (at the time) were the insurance companies who'd offered premium reductions for ABS-equipped vehicles!

I still think ABS is a good deal, even though I don't usually (ever?) drive in situations where it would help. However, if I get caught out on the I-slab (Interstate) in the rain, and some id*t changes lanes in front of me, well... that's what it's for. Without it, you might only need it once; but with it, you might be around to need it again.

Also, I don't believe ABS is nearly as "smart" as it could be and ought to be. I have an idea that I believe will greatly improve its operation, but I can't tell you because it might keep me from reaping the 498-million dollar licensing rights. (I'm kidding about the money, but not about the improvement)

ONE LAST ITEM:
Speaking of needing ABS: Has anyone noticed how arrogantly crazy 18-wheeler jockeys have become in the last 5-or-6 years? This seems to be the case here in the Southeastern USA. If you're younger 40 you might not remember it but, in the 50s and 60s, truck drivers were--in general--among the most courteous & professional drivers on the road.

Oh well, car drivers have become this way so the truckers must feel they need to "keep up with the Joneses."

GeronimoPFudgemuffin