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Mark,
No problem, ask away as I'm happy to
educate/inform if I can.
The bias is determined in the master
cylinder and it even varies by brand even for the same size. eg Nabco has a
slightly different built in bias than Tokico as has Sankyo etc etc. It's done by
the valving and springs in the cylinder. Dual cylinders are designed to be used
with a prop valve and this is your problem. I got lucky on my street 1600, I had
a 3/4" Tokico that decided it didn't want to work no more and I'd lent my spare
out. OK, off to the JY for something to keep me going and reluctantly I bought a
smick Sunny 13/16" Nabco - same fittings except for the prop valve, so I left it
off - it was only going to be temporary right. Turns out that this cylinder is
far superior for my setup without the prop valve, and 2 years on I'm still
running it and the other cylinder and prop valve is still in the spares box. I
tell the story to illustrate that there's no way that unless you run exactly the
same components as me that I could guarantee you'll get the same result - it
just don't work like that with brakes.
What a prop valve does is alter the
front/rear pressure by blocking the rear pressure - unless you have a
sophisticated tilton type then the stock production valves don't even increase
the pressure to the front for the same pedal pressure.
All that a booster does is use manifold
vacuum to lessen the pedal pressure (effort) required to move the fluid
from the master cylinder onto the slave cylinders - it does nothing more and
nothing less.
I suggest you have a read of this article -
it contains some American terms but you'll work out what they are talking about
eg prop valve is called a combination valve in US. Some of the stuff about how
hydraulic systems work is a bit basic but it will tell you how a change of
master cylinder bore diameter affects the force applied to a slave.
regards
Terry
Terry,
Sorry to be harping on this subject, but can you explain to me - is it
the booster or master that affects bias?
If its the master cylinder, then with the previously mentioned setup what
master would you suggest so as to eliminate the bias.
Mark
----- Original Message -----
Sent: Thursday, May 30, 2002 1:21
AM
Subject: RE: Brake Booster
Mark,
That combo would have very similar
piston diameter to the 180SX so I think 15/16" cylinder would be a good one
to start with. It's always a bit hit & miss when you migrate brakes but
it's going to be close. Sunny booster is fine, should be nice stoppers when
you get them sorted. If you're lucky you wont need a prop valve, but it's no
biggy to fit one. My feeling is that you'll need one as the 15/16" cylinder
just may send too much pressure to the R31's in the rear and you don't wont
premmy lockup. With the big 4 spots in the front you really don't want much
more than 20-25% going to the rears in a much lighter car than brakes
of that capacity are designed for. I've never used an Urvan cylinder but if
it's a Tokico or Nabco with the lines out on the correct side or even better
underneath then it will be fine.
regards
Terry
I am intending on running 285mm R32 discs and R32 4 spot
sumitomo claipers at the front with R31 discs and 2 spot genuine
nissan calipers on the rear.
What I want to achieve is a good feeling pedal without the need for a
bias valve. If I can find the parts required I want to then get them
new.
What is your opinion on the Sunny Booster and Urvan master cylinder?
Any other suggestions?
Your assistance would be helpful.
Cheers
Mark O'Connor
----- Original Message -----
Sent: Tuesday, May 28, 2002 7:32
PM
Subject: RE: Brake Booster
Mark,
What brakes (front & rear, discs
& callipers) do you intend to run as it depends greatly. I've not
seen a lot (none actually) that have had success with a 15/16" cylinder
and the car I'm thinking of now has a 13/16" Sunny and it's a good feel.
I have no problem with the Sunny booster, it's much the same as a
Japanese 180B & SSS anyway.
regards
Terry
Thanks Terry,
Im not too sure! I was told to go with a Sunny Booster and Urvan
Master (being 15/16th)
Any thoughts or other suggestions?
Mark
----- Original Message -----
Sent: Monday, May 27, 2002
10:12 PM
Subject: RE: Brake
Booster
Mark,
Do you mean 15/16" master
cylinder? Sunny has 13/16" and same booster as 120Y (11/16"), 15/16" cylinders are off 180SX and
not much else that I know of and SSS had some a while
ago.
regards
Terry
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