You need to be careful changing prop/combo valves. Since the brick has
disc/drum, you need a combo valve (prop and meter). The metering slows down the
inital apply rate of the disc brakes since inherently disc brakes apply faster
than drums do to the engagement distance drums require. Getting the metering
right is important, but not as critical as getting the proportioning right. The
prop valve has two distinct parameters when sizing them, the slope and knee
point. The knee point is the point at which the ratio goes from 1:1 to the
slope ratio. The brake configuration (caliper size, rotor effective diameter,
lining material, etc) and vehicle weight distribution will determine your Z
critical (the vehicle deceleration at which your vehicle goes from front biased
to rear biased). Typically, a brake system is designed to be inherently rear
biased (for parking brake effectiveness and failed systems and such) so a prop
valve is used to move the bias to as close to neutral as possible for all
loadings while remaining slightly front biased. So, trying to cut to the chase,
changing your prop to an aftermarket can cause you to be rear biased which
caused worse brake performance and can cause the vehicle to oversteer since the
rear wheels will lock before the front ones. An aftermarket prop can also cause
you to be front biased which is safer because it doesn't induce oversteer, but
it still decreases overall potential braking. That's why the prop for the Brick
is unique. As a side note, most new vehicles don't have a prop valve because
they have ABS. ABS can electronically control the rear pressure and does a
better job, giving a neutral bias for all loading conditions.
Seth
ABS/TC/Stability Control Vehicle Development Engineer
#1544
*********** REPLY SEPARATOR ***********
On 4/7/2004 at 3:13 AM High Tech Coatings wrote:
>try www.mpbrakes.com they have valves, boosters and masters as well as
>disc
>kits for hotrods etc.
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