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Help! Gen 3 Turbo Brakes w/ 1" MC & N/A prop valve locking up front brakes

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3sgeTurbo
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2016/11/02 17:46:06 (permalink)
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Help! Gen 3 Turbo Brakes w/ 1" MC & N/A prop valve locking up front brakes

Hi guys, I have an issue where my front brakes lock far too easily, especially in the wet.
 
The car:
1990 JDM SW20 N/A Manual (non-abs) with Gen 4 3SGTE
1993+ Gen 3 Turbo brakes
Thin N/A Brake Booster
1990 N/A proportioning Valve
4 Runner 1" Master Cylinder
Tyres are Federal 595's
 
I am thinking that it might be the n/a prop valve, I have read contradicting information that the N/A and Turbo's have different brake bias or that maybe the 1" master is too big?
 
Appreciate any advice.

1991 MR2 Black Turbo Targa Gen 4 3SGTE w/ GTX3076r
1984 AE86 Toyota Sprinter 4AGE 16V ITB's
2002 BMW Silver X5 4.4i V8 Daily Driver 
#1


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    Reddtarga
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    Re: Help! Gen 3 Turbo Brakes w/ 1" MC & N/A prop valve locking up front brakes 2016/11/03 16:42:57 (permalink)
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    Firstly, I don't know what may be causing your problem, however the turbo and NA Prop valves are different in their operation. Google up 'Brake bias Knee Point' 
    The M/C bore size will mainly only affect pedal pressure needed, and pedal travel.
     
    Your system looks like a bit of a mixture.
    As well as a later model turbo prop valve, maybe look at also updating the booster. The post '94 ones are probably the best ones to get and are a lot more powerful than the early model NA ones. You would also need a separate check valve. Your one inch master may still be OK even though 15/16" is the OEM size. 
     
     

    1990 ADM NA
     
     
     
     
     
     
    #2
    track_mr2
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    Re: Help! Gen 3 Turbo Brakes w/ 1" MC & N/A prop valve locking up front brakes 2016/11/04 07:38:01 (permalink)
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    The easiest and cheapest option might be to fit an adjustable brake bias valve.
    #3

    5SGTE
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    Re: Help! Gen 3 Turbo Brakes w/ 1" MC & N/A prop valve locking up front brakes 2016/11/04 16:36:35 (permalink)
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    Some feedback about my set up which is very similar to yours,
     
    1991 JDM SW20 Turbo
    1993+ Gen 3 Turbo brake Calipers
    Stock Brake Booster
    1991 Turbo proportioning Valve
    4 Runner 1" Master Cylinder
    Tyres are Federal 595rr's
    Supra BBK front
    RX8 BBK rear
     
    Basically feels like the stock setup but with more bite and slllightly more pedal movement prior to initial brake contact.  Bias feels as it was with the '91 calipers.
    #4
    3sgeTurbo
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    Re: Help! Gen 3 Turbo Brakes w/ 1" MC & N/A prop valve locking up front brakes 2016/11/04 18:27:35 (permalink)
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    Thanks for the response everyone. I have sourced a 91 Turbo prop valve and will give it a crack.
     
    I do have one of the late model brake boosters but have not yet fitted it yet.
     
    Will keep you all updated.

    1991 MR2 Black Turbo Targa Gen 4 3SGTE w/ GTX3076r
    1984 AE86 Toyota Sprinter 4AGE 16V ITB's
    2002 BMW Silver X5 4.4i V8 Daily Driver 
    #5
    5SGTE
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    Re: Help! Gen 3 Turbo Brakes w/ 1" MC & N/A prop valve locking up front brakes 2016/11/04 18:48:34 (permalink)
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    Do you need modify the hardlines when fitting a slim booster?
    #6

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