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RE: Dual master cylinder (my last take)

To: Randall <>
Subject: RE: Dual master cylinder (my last take)
From: Barry Schwartz <>
Date: Thu, 27 Apr 2000 13:13:11 -0700
References: <>
Don't get me wrong, I never said that they didn't work at all, I just doubt
their effectiveness as a fail safe backup.  Of course any help is better
than no help in an emergency situation.  I'm just relating from personal
experience, and in both cases mine failed without warning, and without
braking on both my dual system vehicles.  Now, I don't advocate switching
from dual to single systems either.   While I will argue the effectiveness
of anti-lock braking, there are many studies that show that ABS isn't all
that effective (simply because drivers aren't used to the pulsing pedal and
they let off the brakes thinking something is wrong), yet they are being
equipped on many new vehicles.  Disk brakes on the rears aren't *really*
necessary as drums will stop the back of the car quite effectively, and are
much cheaper to manufacturer and certainly easier to incorporate the
parking brake, yet many cars sport rear disks, etc.

I guess my point would be (originally) why go to the expense, and trouble
of fitting a system that is more complex, and *potentially* troublesome
that may or may not always do what it is intended to?  If it gives you
piece of mind then, go for it - I wouldn't loose sleep over it.
>Dual circuit brakes certainly add to the cost of the vehicle (as does ABS).
>Why would any manufacturer put them on if they didn't work ?
Remember what I said above about reliability I have two perfect examples of
complete failure so they don't always work as intended and I'll be the
first to admit that in both cases the master went.  I contend that if the
system was TRULY designed as a fail safe system you would have two SEPARATE
masters and if one failed, then I would still have the other (what the dual
circuit is supposed to do but doesn't always achieve, because of the common
bore with the resultant leakage of one into the other without any
indication of anything is wrong until it's too late). The likely hood of
two failing at the same time is much more remote, and much more obvious
when one of the two is starting to fail, but that would add complexity and
even more expense.  I suppose that one could argue that a master for each
wheel or two duals each with their own line would be even better or a
redundant system such as used in aircraft would be even more effective, but
there are limits.  Suffice it to say the systems that we have today satisfy
the law, without increasing the cost too much and probably help in certain
situations.  And as with everything it's a compromise, that answer is easy,
dual circuits are required by law - (mandated safety requirement) How its'
achieved I suppose is entirely up to the manufacturer. 
I'll not clutter the list with any more on the subject, but feel free to
comment off-line. 
I'll remain firmly un-convinced as to the overall effectiveness of dual
braking circuits as my own personal experience tells me so, or until a
system I use proves otherwise.  I give em a C+ - in more than one case -
Nuff said :-)

Barry Schwartz (San Diego)

72 PI, V6 Spitfire (daily driver)
70 GT6+ (when I don't drive the Spit)
70 Spitfire (long term project)

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