5 replies to this topic

[ZAK308]

Hi
I have converted my LX to Commodore 4 wheel discs. Although it now pulls up much better, I want to adjust the front/rear brake bias.
I am doing this on a budget so am trying to modify the original proportioning valve, rather than change to Commodore style booster and master cylinder. My questions are:

1. What was the 'crack point' for an A9X propotioning valve?
2. Do any other holdens run a similar crack point to A9X?
3. Can the internals from a commodore style integrated prop. valve be interchanged with my torana prop valve? (the internal all look similar in the Gregory's manuals)
4. Are there any other ways to easily (read cheaply) modify the crack point, without resorting to an adjustable racing type valve.
Any comments would be appreciated.
Thanks

[fuzzypumper]

1. dont know.
2. dont know but HZ Statesman Disc/Disc had 450 crack on the prop valve.
3 & 4. You may be able to use the spring in the commodore combo Mcyl prop valve which is 350 C.P.
in the Torana prop valve (dont know if anyone has this it may not have th same circular diameter to fit)
but I doubt any of the other parts would fit.

Edited by fuzzypumper, 08 October 2009 - 07:33 PM.

[76lxhatch]

I'm guessing you want more bias toward the rear? What discs and calipers are you using? With Hoppers twin piston 290mm front and R31 Skyline 260mm rear brakes I found that mine works very well without the proportioning valve.

[dattoman]

Hi
I have converted my LX to Commodore 4 wheel discs. Although it now pulls up much better, I want to adjust the front/rear brake bias.
I am doing this on a budget so am trying to modify the original proportioning valve, rather than change to Commodore style booster and master cylinder. My questions are:

1. What was the 'crack point' for an A9X propotioning valve?
2. Do any other holdens run a similar crack point to A9X?
3. Can the internals from a commodore style integrated prop. valve be interchanged with my torana prop valve? (the internal all look similar in the Gregory's manuals)
4. Are there any other ways to easily (read cheaply) modify the crack point, without resorting to an adjustable racing type valve.
Any comments would be appreciated.
Thanks

1. 225 (and its built into the master cylinder like a Commodore)
2. Yeah.. commodore runs 225 VB-VP or so
3. Never tried... good luck.. let us know how it goes. Crack pressure is determined by the spring... so thats the part that needs changing
4. Spring...

Now.. if you have Commodore brakes on your car... thats got nothing to do with an A9X as they are different rear calipers so the crack pressure you require might be different

The easiest way is to delete your factory prop valve and fit an adjustable one
Since nothing can compare to dialing in your own based on your brakes, suspension mods and tyres

The grip you have has nothing to do with any factory Holden ever produced.
So you can't really fit something off another car and hope it will be spot on

[TerrA LX]

Are adjustable bias valves "proportional"?

[ZAK308]

Thanks for the comments everyone. I am running VL turbo calipers on the rear, and single piston vr calipers on the front. I see your point Dattoman that the A9X crack point is not relevant, as there are too many other variable to take into account.
I was hoping to avoid an adjustable prop valve, as I wanted (as much as possible) to maintain a standard looking engine bay.
I have access to some commodore master cylinders, so I might try the spring swap and see how this improves things. It should be a fairly inexpensive experiment. Who knows, it may even work!
If this fails, I might consider the adjustable valve, or possible a complete A9X style conversion.
Will let you know if it all works well.
Cheers