Anti-Lock Brakes

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PolicySpy wrote:


Seriously, what the hell?
Have you ever driven a car?
--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel
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Nate Nagel wrote:

One wonders. A whole string of fact-free fiction posts in reply to himself.
If you type it enough times, it must be true... right??? :-p
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I'm beginning to wonder if he has even _read_ about driving a car.
Harry K
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A more serious reply...

It doesn't lock up because the rider doesn't let it. If one were to lock the front wheel of a motorcycle under braking, Really Bad Things would begin to happen Really Fast, the end result being a case of road rash.
That does not mean that the rider cannot force the front wheel to lock up if he for some reason he wants to (or, alternately, of the CoG is high enough, the motorcycle will flip end-over-end before the front wheel locks.) It just means that his self-preservation instinct is such that he will not allow that to happen.

No, it's defined as stopping in the minimum distance.

OK, I'll buy that.

Ultimate-braking? what's next? Stupendous-braking?

That's true of ANY vehicle. If you lock the wheels, the coefficient of friction between the tires and road decreases. Therefore, lots of people have spent lots of time, money, and materials trying to design braking systems that will allow the driver to come right up to that point before the wheels lock and be able to hold it there (and/or achieve this goal by other means, e.g. ABS.) This is not an ultimate brake torque issue - if you need more brake torque that's easy enough to achieve by any number of methods (larger diameter rotors or drums; higher coefficient brake linings; changing the pedal ratio and/or ratio of master cylinder bore to wheel cylinder bore; adding assist devices such as vacuum or hydraulic actuated power boosters.)

Proof of what? That a motorcycle has a high center of gravity and short wheelbase compared to a car? Most people already knew that.
nate
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This is -- of course -- a totally different situation, caused by the fact that a motorcycles centre of mass is much higher in relation to its wheelbase.
Nevertheless, a racing motorcycle's front tire can still be locked up by the brake.
--
Alan Baker
Vancouver, British Columbia
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PolicySpy wrote:

nASScar still does it that way, and the lateral rod adjuster is controlled by a knob on the dash so the driver can make changes in brake bias as needed. Most of the rest of the world uses proportioning valves.

You still don't get it. Proportioning only ensures that no wheels lock up prematurely as you add braking pressure. But it does nothing to prevent lockup in general. Nor do you want it to, braking to the threshold of lockup is good driving technique.
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Any new car that can't lock up its brakes (ABS disabled, of course) under ideal (clean, dry, good road surface, warm temperature) conditions has defective brakes. Period, end of story.
I'm not trying to be deliberately contrary, or even unnecessarily argumentative - but your understanding of the subject is seriously flawed.
Yes, older cars had narrow, bias ply tires, but as tire technology has improved, brakes have become more powerful as well. That said, the 50 year old brakes on my Stude still lock up modern tires. The main improvements in brakes since that time are not in overall brake torque, but in fade resistance and ease of modulation. Modern disc brakes with big, chunky calipers are much stronger and flex less, therefore they are easier to modulate "at the limit."
nate
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Uh... no. They were set up as I described before, to insure that front and rear locked about the same time, given an equal surface for all 4 wheels and allowing for weight transfer during braking.
And old cars also had narrow tires...
Depends on the "old car." My '66 has P255 traction "A" rated radials on it. And it can lock all 4 of them up. The only modification to the braking system was to put a set of 1972 front disks from the same chassis type- a bolt-in upgrade- and the matching prop valve on it. All factory parts.
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You sure about that? Been a long time but I recollect hat the master cylinder only had one pump that fed all four brakes and no special valving.

You just said in para 1 that old cars also proportioned the braking.
Harry K
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u never can tell what would have happend
--
kingkev
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Now my anti-lock brakes are back to normal...
It was just a combination of taking out the fuse, driving the car, and putting the fuse back in. And clearing the computer by disconnecting the postive battery cable. And clearing the computer with a code-reader. And also being connected to the state emission computer. Some combination of the above...
And the anti-lock brakes being back to normal is confirmed with coasting tests during the problem and after...
Now the problem was that the anti-lock brakes seemed to be dragging with the fuse in and not with the fuse out. Also the traction-control light could light up showing a moment of usage when usage would not be required. And there were no error codes...
But confuse the issue some more...the power steering is lighter with the ABS fuse in .
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