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
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.
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.
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
Nevertheless, a racing motorcycle's front tire can still be locked up by
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.
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
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."
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
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
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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