[DeTomaso] removing second set of stock rear brake calipers?

[Tomas Gunnarsson]

Very few cars have master cylinders that produce different pressure
front/rear. Differences in volumetric capacity (i.e. amount of cylinder
stroke) has no impact on brake force.

Tomas
  -----Original Message-----
  From: Julian Kift [mailto:julian_kift at hotmail.com]
  Sent: den 7 mars 2010 21:32
  To: guson at home.se; pantdino at aol.com; De Tomaso List
  Subject: RE: [DeTomaso] removing second set of stock rear brake calipers?


  IMHO the necessity for the proportioning valve depends on your aftermarket
master cylinder and the volume ratios front to rear (assuming you have a
tandem M/C). There are spreasheets available on the web that calculate
various aspects of the braking system; recommended M/C bore size and front
to rear braking bias, based upon vehicle weight, C of G, wheel rolling
radius (tire width doesn't come into it), disc size, pad contact area etc. I
would recommend anyone upgrading or modifying brakes to obtain such a
spreadsheet for guidance.

  Most modern braking systems have the proportioning valve in the rear line,
but as said if you have far more front than rear that's not going to do much
good.

  Julian

  > From: guson at home.se
  > To: pantdino at aol.com; detomaso at realbig.com
  > Date: Sun, 7 Mar 2010 19:38:29 +0100
  > Subject: Re: [DeTomaso] removing second set of stock rear brake
calipers?
  >
  > The stock prop valve is there to prevent premature front wheel lockup.
With
  > dual rears it may not be necessary. If you remove the extra set the
valve
  > should go in again. That said, the dual calipers are not likely the
cause of
  > your drag. I have dual calipers per side (one stock, one other) on my
car
  > and the drag is not notably different from one caliper per side. Your
drag
  > should go away with a general overhaul.
  >
  > Tomas
  >
  > -----Original Message-----
  > From: detomaso-bounces at realbig.com
  > [mailto:detomaso-bounces at realbig.com]On Behalf Of pantdino at aol.com
  > Sent: den 7 mars 2010 19:11
  > To: detomaso at realbig.com
  > Subject: [DeTomaso] removing second set of stock rear brake calipers?
  >
  >
  > When I got my car 20 yrs ago the PO had installed a second stock caliper
on
  > each rear wheel. I suspect as a result the car has always had more brake
pad
  > drag, evidenced by resistance to rotating the wheel by hand or pushing
the
  > car. (The rotors are not warped-- the resistance is steady.)
  > I believe the cars came with a brake proportioning valve, which was
removed
  > when the aftermarket (GM I think) master cylinder was installed. (Again,
by
  > the PO). My understanding is that said proportioning valves are to
prevent
  > rear wheel lockup.
  > I would like to remove the redundant rear calipers to eliminate the
extra
  > drag, and my question is whether I have to reinstall a proportioning
valve
  > if I do that.
  > I am running 285/40-17 and front 215/45-17 front tires, Goodyear Eagle
F1.
  > Looking at that puny rear pad I find it hard to believe that it will
lock up
  > that wide tire before the larger front pads will lock up the much
narrower
  > front tire.
  > So I'm thinking removing the extra rear caliper will not require a
  > proportioning valve.
  >
  > I'll disassemble the calipers also to check their condition after 20 yrs
of
  > silicone fluid use.
  >
  > Jim Oddie
  >
  >
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