P. J.
Glazed pads or rotors can increase pedal pressure, so make sure that's
not the issue -- you could remove the pads, clean them up, and lightly
sand the rotors/drums. Kas' book mentions putting a pad in a wooden
holder, chucking an end cutting tool (like a router bit) in a drill
press, and sliding the pad around under the bit, exposing new material
while leveling out the pad thickness (in his case, done to decrease
initial pedal play rather than improve brake effectiveness, but I can't
see why you couldn't use that technique to try to rescue a set of used
pads with a lot of meat left on them).
If the stock brake pads have been overheated or the pads/shoes are
contaminated, pedal pressure can go up. Due to the dual master cylinder
setup, leverage may have changed, so changing pad friction compound may
be the easiest to improve things. I had a street VW R32 with which I
wanted to do some track work with so I replaced the stock pads with Hawk
HPS street high performance pads and those, once heated up, would haul
the car down like I had an additional brake booster. As the car slowed
from high speed, retardation rate would continue to increase without any
increase in pedal pressure. They have an elaborate break-in procedure
that you must follow to get best results, by the way. However, they
produced a bit of black brake dust and squealed if lightly used when
cold, so they're not my choice for a car that's mostly street driven.
I'll also second the suggestion of Porterfields. I used their RD-4
vintage racing compound on the Morgan race car and, similarly to the
Hawk material, they really had good bite when they heated up.
Porterfield will make you what you want if they don't have them in stock
-- you might have to send them an old brake pad. Friends have used RS-4
on street vehicles and have reported lower pedal pressure to the point
where some felt they could remove the brake booster without having
unacceptable pedal pressure.
Lastly, if someone has swapped from DOT 4 to DOT 5 or vice versa, mixing
the two can cause the brake fluid to get very viscous. A friend of mine
mixed the two inadvertently when trying to limp home from a weekend
event using a donated bottle of brake fluid to continually top off the
reservoir level, which kept dropping due to a small leak in a brake
line. I tried to stop his car after it had been repaired and no amount
of force applied by a human would stop that car adequately. He described
the stuff that he bled out as having a consistency of silly putty. The
system had to be disassembled and cleaned with alcohol to remove all old
brake fluid.
(I'm afraid I have to disagree with Bill T. -- smaller master cylinders
will reduce pedal pressure at the expense of more pedal travel (greater
number of inches of MC piston stroke per unit of fluid moved -- and
therefore less work done per inch of stroke -- is equivalent to pushing
on a longer lever, mechanically speaking), so I don't think you want to
go with bigger.
Duncan
On 8/23/14, 10:22 PM, McKearn McKearn wrote: > Hi. > I'm looking to
improve the brakes on My GT6. I currently have stock > brakes with
nothing special pads. Dual master cylinders with 5/8 pistons > and
balance bar. Rotors are drilled . The car will stop but It seams like >
it takes some serious pedal pressure and if you want to stop NOW you
have > to push with all you've got. I think the balance is pretty close
as the > fronts will lock up first but I just feel like something's
missing in the > brake department. This is a street car (for now) I have
considered ceramic > pads but really don't know if that would help or
not. Any suggestions would > be appreciated. > Thanks. P.J. >
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