RE: Bleeding Dual Circuit 69 Brakes Again and Again and...

[Scott Fisher <sfisher71@domain.elided>]

--- Brian Shorey <bshorey@domain.elided> wrote:
> this means that the brakes should have the same
feel,
> and require the same volume of fluid to be pushed
> into the caliper, to actuate them, whether the pads 
> are new or worn.

On further thought, I'm with you up to that point, but
the "feel" issue for Alfa brakes depends, I'm
convinced, in large part on how well the pads are
working.  What I now think was going on with MY
Berlina was this: worn pads cause the driver's right
leg to enter a subconscious feedback loop -- I press
the brakes and the car doesn't slow down much, so I
press harder (and the vacuum assist translates this to
more pedal travel) and I STILL don't slow down much,
so I press harder STILL (and the assist translates to
still more travel), and I STILL don't slow down much. 
Result: my foot has traveled a long way without much
effect OR much effect, and the brakes "feel soft."  

What's happening now that the new pads are getting
bedded in: I press the brakes and the car slows down a
bit as they begin to "bite," so I press the brakes
some more and the car slows down VERY rapidly. 
Result: while EFFORT hasn't increased, TRAVEL has
DECREASED, and the brakes don't "feel so soft."

So, Mitch, here's something that might get you to put
the matches away: Turn off the car and start pumping
the pedal.  In about three or four pumps, does the
pedal seem to "rise up" -- that is, does the same
effort result in less travel after two or three pumps
with the engine off?  Now hold the pedal down (motor
still off), applying fairly firm pressure.  Does the
pedal move closer to the floor, or will it hold firm
for at least 10 seconds or so?  If the answers to both
of these questions are "yes," your hydraulics are
probably okay, and you can put away the matches
(besides, I think I've found a new windshield. :-)

One other comment that somebody made: check for wear
and slop in your pedal linkage.  I solved a nagging
"brake system problem" on an MGB years ago by
replacing the clevis pin that connected the brake
pedal to the master-cylinder pushrod.  The old one had
been worn through to the point that it looked like a
tiny crankshaft.  And because of the leverage effect
of the brake pedal, that 1/4" of wear at the clevis
translated to over an inch at my foot of dead motion
before the brakes even started to work. 

One final thing for Mitch's peace of mind: while I
didn't address John's question, "Soft compared to
what?" in my response to him, that comparison may be
part of what Mitch is going through, if he's not used
to driving this Berlina (a reasonable guess as it's
been off the road for six months).  Of the five cars I
drive on a regular basis, both of my Alfas have far
and away the lightest pedal effort.  Only the new Mini
Cooper S that I drove a week or two ago has a lighter
pedal in my recent experience -- in Berry's Mini and
in my Spider, I got the feeling that pressing on the
brakes as hard as I do in my Audis would make my
sunglasses shoot off the end of my nose.

In both my current Alfas (and in the Mini), the brakes
feel as though brake pedal RESISTANCE is fairly
constant (and very low), while brake pedal TRAVEL
increases with foot pressure.  This is quite distinct
from the "feel" of my two Audis, in which brake pedal
RESISTANCE increases with foot pressure, while brake
pedal TRAVEL is fairly constant.  Because both Alfas
work similarly to one another and both Audis work
similarly to one another, I'm guessing these are
design/engineering decisions in Arese and Ingolstadt,
respectively.  Which is "better" is a pointless
argument; which one an individual driver prefers is a
matter of personal choice.  (I should also point out
that I've given up doing leg presses in my regular
workouts because the machines at my gym don't go high
enough, so my assessment of "light pedal effort" may
not apply to everyone.)

So Mitch -- if you've been driving "other" cars in
which pedal resistance increases and pedal travel
remains constant, there may in fact be nothing wrong
with your Berlina's brakes.  Try the engine-off tests
I suggest above, and you'll get a better idea about
the condition of your hydraulics.  And I think I'm
going to look at the parts book and see what kind of
connections exist between the pedal and the master
cylinder; the clevis on the MGB cost something like
eighty-five cents, and completely transformed the
car's braking feel.

--Scott Fisher
  Tualatin, Oregon
.
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