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Thread: So lets talk brakes.

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    Senior Member watchdog's Avatar
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    Cool So lets talk brakes.

    Picked up a pedal box with pedals & master cyl/booster for the Morrie for $10. This came off a 1988 R31 Bluebird with 4 wheel discs. Shit of a thing to get out. If I end up using it I imagine I'm going to have to limit the pressure for the rear drums on the Morrie. What is the best way to go about this ? Proportioning valve or limiter ( I think they are two different animals)

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    Senior Member Godzilla's Avatar
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    A little more than that mate.

    Yes a proportioning valve is the way to go.

    Another way is to play with the size of the slave cylinders.

    The thing you need to worry about is you need a one way check valve fitted to the master cylinders rear circuit.

    What happens with drum brakes is that after you have applied the brakes and released them, the return springs pull the shoes back inwards.

    A one way check valve allows the shoes to return a little and then stop returning, which keeps the shoes near the drums.

    Without one what happens is your shoes would be returned all the way back till the slave cylinder pistons reached their inner limits.

    Then when you pressed the brakes, the shoes may not touch the drums, or the pedal may have a lot of travel or need to be pumped.

    Take it into a brake specialist, they may be able to sell you a one way valve to the rear circuit or both front and back if you have 4 wheel drums.

    Other wise just buy a master from a car with rear drums.

    The one way valves normally sit under the point when the brake pipe bolts onto the master, sometimes there is a large nut with the hole and thread for the brake pipe to bolt into, removing it exposes the valve, all depends on the model of master cylinder.
    Last edited by Godzilla; 11-05-10 at 08:16 PM.

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    Super Moderator Fernbay's Avatar
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    Sounds like one of them valve thingies might have been jammed open in an old series II LWB Landrover I use to own many many moons ago. Never could get the brakes right in that thing. Thank god for the hand brake
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    Senior Member Godzilla's Avatar
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    Funny story (now looking back at it)

    I had a car brought to me that had sticking front disc brake calipers (both).

    Pads were always wearing out too quickly, fuel consumption was crap, the car would not roll at the lights when the brakes were released.

    Releasing the brake fluid from the caliper bleed nipples released the pressure and the problem went away till you pressed the brake pedal again.

    To cut a long story short, after pulling the master cylinder apart, i found a one way check valve that was supposed to be used for the rear drum brakes fitted to the front disk brake circuit.

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    Senior Member watchdog's Avatar
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    Cool

    Ah - that would be the residual pressure valve that I've just found out about. Do you know if you can get them as a stand alone unit or are they all built in to the master cyl ?
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    Senior Member Godzilla's Avatar
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    No idea if they are available as a stand alone unit.

    You know, thinking about it, there must be something out there made as a stand alone unit.

    A brake specialist may have a basic valve that could slip into the factory master you have, most cars ive seen have a simple rubber valve that allows the fluid in one direction fitted to the rear circuit.

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    Senior Member Godzilla's Avatar
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    Google says yes.







    Just be careful you dont get a 2 Lb one which wont hold against the Drum brake return springs, looks like 10Lb is the go for drums, 2 Lb for disc setups where the driver wants less pedal travel going by Wilwoods website.
    Last edited by Godzilla; 11-05-10 at 10:59 PM.

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