Proportioning Valve

[SlimLim]

Hi all,

I'm wanting to put a proportioning valve into my braking system to adjust the bias. I'm using the 13" cobra fronts, with mk4 2 pot rears. I have ABS and I am keeping ABS.

From my calcs i'll be having too much rear bias so i need to shift it to the front, or at least have the ability to do it. Does anyone know if there's any adjustable proportioning valves that will install with minimal work?

What is the thread and pitch of the stock brake line connectors?

Am i correct in saying you put the prop valve on the rear brake lines, not the fronts?

 

[IJ.]

You can only take away from the rears to alter the bias with a valve, wouldn't run one in the front circuit.

 

[SlimLim]

Any issues with ABS IJ?

 

[Poodles]

There's already a proportioning valve in the stock system, plus ABS will keep things in check regardless. Easy way to test if you're too rear heavy is to disable the ABS (pull the fuse) and lock the brakes up in a safe area. Can't do it without disabling ABS or it will just kick in and you won't know if the fronst or rears are trying to lock.

 

[SlimLim]

Cheers. My engineer says to install one, because we are going to the brake dyno, and i don't want to have to pay for it twice.

Do you know the thread and pitch of the stock fittings? Any specific proportioning valves people can recommend?

Has anyone got pics of their installs?

 

[IJ.]

M10x1 from memory, stock Prop valve is non adjustable, guess if you're going to test on a brake dyno there might be gains to be had, let us know how it all goes Slim!

 

[SlimLim]

Sweet.

Won't be on a brake dyno for awhile, but i'll keep you posted in my build thread.

So, what do you think about using this one? http://www.summitracing.com/parts/TIL-90-1003/

Do i need to replace the entire stock prop valve, or can i just keep i, and run the rear brake lines into it? The install of it all is still a bit hazy to me.

 

[IJ.]

Not really sure what's inside the stock one but I'd remove it and run the Tilton in the rear circuit, I used to run one in my old Z car with the TT v8, it had a 120 litre fuel tank and as the car only weighed 1100Kg's wet full/empty had a HUGE effect on handling/braking.

Silver knob between the seats, black knob was the MBC.

 

[Supracentral]

Cheers. My engineer says to install one, because we are going to the brake dyno, and i don't want to have to pay for it twice.

I have to admit, I came into this thread expecting idiocy. I am pleasantly surprised I'm 100% wrong. This is how you do it folks.

Let us know what the dyno teaches you about the MKIII braking system - it's a topic I don't think many of us know enough about.

 

[IJ.]

I have to admit, I came into this thread expecting idiocy. I am pleasantly surprised I'm 100% wrong. This is how you do it folks.

Let us know what the dyno teaches you about the MKIII braking system - it's a topic I don't think many of us know enough about.

:love: you to Boss .....

 

[Poodles]

Yeah, the ABS system will mask any issues in the brake bias. Vehicles are tuned to lock the front up first from the factory, but once you start changing things, all bets are off.

Rear lockup is scary shit in an emergency situation. My old truck had a system that adjusted rear braking on the fly based off of the load on the bed (basicly a valve on the rear axle with an arm that went to the bed of the truck). Valve worked fine, but the arm was bent. Nothing like going sideways in the middle of traffic because of some dumbass cutting you off and slamming on their brakes in the rain...

 

[SlimLim]

Glad i got some thumbs up for this.

I'm a little surprised noone has actually put a supra on a brake dyno before.

I can't have an in car bias adjuster as it's deemed dangerous (and rightly so if you don't know what you are doing). I have to prove that there are safety mechanisms in place so the prop valve can't be accidently changed without notice. So i'm getting a lever style, rather than a knob style, as it's easier to set and fix.

So correct me if i'm wrong but the install should be to keep the stock prop valve for the fronts, cap off the remaining inlet/outlet to the stock prop valve. Reconfig the rear lines into the tilton prop valve? Doesn't have to go back into the stock prop valve?

But to the Tilton...that's a yay or nay to it? It's the only M10x1 type on the summit site. Can anyone give me a second on the pitch and thread (metric makes sense on a jap car anyway)?

 

[Asterix]

Yeah, the ABS system will mask any issues in the brake bias. Vehicles are tuned to lock the front up first from the factory, but once you start changing things, all bets are off.

It seems to me my right front sets the ABS off first consistently on dry pavement, but that's just a feeling.

(Veering a little off topic) My '04 350z is most definitely biased towards the rear. I know this both by how the rear pads go away faster and guys that race this car complain about it. I'm going to try and change that by using less grippy pads on the rear next time I replace them.

 

[Poodles]

Yeah, lots of modern cars can get away with being slopping since there's tons of techno-gadgetry to handle bias on the fly.

 

[Dylan JZ]

I hope to do this as well (properly/professionally) when I move to BBK.. my ABS has been off ever since my 1J/R154 was put in.

 

[SlimLim]

I'm just installing this now into my RHD ABS equipped car.

I am planning on removing the stock prop valve, replacing the rear brake line with the adjustable tilton prop valve, and connecting the front master cylinder brake line to the stock T fitting (directly to the ABS unit).

I just want to confirm that the front brake lines from the brake master cylinder, may be bypassed from the stock prop valve, and the brake line may go directly into the stock T fitting (near the brake booster).

 

[SlimLim]

is it easier to explain this in a diagram?