260z rear brake issue | Page 2 | The Z Club of Great Britain
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260z rear brake issue

Discussion in 'S30 (240Z,260Z,280Z) Suspension,Brakes and Steerin' started by Peato40, Jan 29, 2018.

  1. Peato40

    Z Club Member

    Many Thanks Albrecht, much appreciated. I'm going to open up that proportioning valve again and see what's going on.
  2. toopy

    Z Club Member

    Am I right in thinking that the proportioning valve, is to help reduce the possibility of the rear wheels locking up before the fronts under heavy braking

    If that's the case, how exactly does it achieve that?
  3. Peato40

    Z Club Member


    Okay, so I removed and stripped the proportioning valve again and this time studied it in more detail to understand exactly what is going on.

    What I concluded is that the valve will pretty much allow free flow of oil to the front brakes, whereas it slightly restricted to the rears. In the event of the pressure rising very high in the from system, the pressure will defeat the spring tension and move the plunger which in turn then further reduces pressure to the rears.

    Now what I discovered is that I had an addition part in my valve, which I can only guess was somebodies attempt at changing the bias. If you look at the attached photos you will see that there is a copper spacer, which is not evident in the pictures from the workshop manual that Albrecht kindly donated. With this spacer in, I was getting zero flow through the valve to the rear circuit and when I rebuilt without the spacer I then got restricted flow and then upon raising the pressure on the front side of the circuit the flow on rears pretty much stopped.

    My only concern is that this copper spacer might be something that is used only for 2+2 models, so I'll keep it until brake bias can be properly tested. :thumbs:

    Attached Files:

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