Ok.

Set-up is this.

OEM Subaru/Sumitomo 4pot/2pot brakes.
OEM single stage booster
OEM WRX/STI Master Cylinder

Master cylinder has 2 ports a front and a rear. The front port goes to a Tee-fitting, and to the front brakes. The rear port goes through an aftermarket proportioning valve, through a hand brake master cylinder, then into a t-fitting, and out to the rear brakes.


The front brakes seem to be doing WAY more braking than the rears. The fronts pads will be cooked, and the rears are perfect.

The front brakes lock up way before the rears, causing the car to push.

I'm using the same pads front and rear.

doesn't seem to make much difference if the prop valve is set full in, or full out.

Have i screwed up the plumbing?


I know the crappy prop valve is junk, and not ideal.



A friend runs the same calipers, same mastery cylinder....no booster (been removed) and a dual banjo fitting on one of the ports of the M/c. One line for the front brakes, one line for the rear.


Do i just ditch the prop valve?

This should be a fairly standard OEM set-up, but something seems wrong.

---

Chris

I've had el-cheapo proportioning valve fail with results similar to what you describe Chris.. basically no rear brakes. Get rid of it and see what they are like, Them put a new one in.

Note: When I ran stock master there wasn't enough rear brake to run a proportioning valve on the rear... you can't reduce the rear brakes if you already don't have enough. I worked around this by reversing the lines at the master... there was some proportinoning built into the master, so reversing put more brake to the rear, then the proportioning valve could do something... Nissan vs Subaru, Who knows if any of this is relavent.

-Martin.

ageed, ditch the "limiter" first.
Just try them out.
I've set a bunches of friends without limiter--or proportioner or whatever al long as i stock with my "cure-all" Volvo 240 caliper with 2 x 1.5"/38mm pistons

Tryit.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

MRWmotorsports Wrote:
-------------------------------------------------------
I worked around this by
> reversing the lines at the master... there was
> some proportinoning built into the master, so
> reversing put more brake to the rear, then the
> proportioning valve could do something... Nissan
> vs Subaru, Who knows if any of this is relavent.
>
> -Martin.

In the old days there were several cars with this type of master cylinder. Its a staggered bore master. Normally all of these OE m/c's have 2 pistons but some had a smaller bore/piston in the front with a bigger in the rear, that effectively set the pressure bias.

This however no longer occurs because cars these days have a diagonal (or X if you may) line setup because of the abs system, so the m/c ports runs the FL/RR and FR/LR on all cars. So I doubt you really "fixed it" by doing that, bleeding and rebleeding sometimes fixes things like that.

As for the no rear brakes on Chris's setup the rear calipers have such small pistons that the only way to go about it is with more aggressive rear pads OR put the prop valve on the front line, but this is not realy the way to do it!

So.

Just ditch the prop valve in the rear brake line?
Cost - likely just a brake line union fitting...couple bucks.


Or...really go dual masters?

i am thinking i could do it fairly creatively. I think i can probably modify the stock pedal box to use twin masters, much like John does with the Xtrattie stuff.

Does anyone know the pedal ratio on the OEM Subaru Pedal box? Has anyone tried doing this?

The way i see it is a couple of master cylinders (ebay it), a balance bar, and some fabbing on my end.



How much better are these brakes going to be with a dual master set-up? I know the Calipers are not blingy stuff, but the front cast iron puppies do work just fine, and the rears are alloy (which get worn away), but they should work just fine as well. They are also a dime a dozen, along with the rotors.


What size masters should a person be using?

And how come everyone else running this set-up is not having problems? Theres lots of others using this stuff.

---

Chris

Chis--I have a vague memory of pedal ratio being just over 4:1

Hey what about this "dime a dozen" for the Subie rear ALLOY caliper..
Is it vented disc?
Dime a dozen?

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

I guess i can measure tonight.

Well. not really dime a dozen, but they are available from the dealer new for like $200 each.

The rotors are easily found, and pads are the same as a 300zx Nissan.

---

Chris

Do It Sidewayz Wrote:
> Or...really go dual masters?
>
> i am thinking i could do it fairly creatively. I
> think i can probably modify the stock pedal box to
> use twin masters, much like John does with the
> Xtrattie stuff.
>
> Does anyone know the pedal ratio on the OEM Subaru
> Pedal box? Has anyone tried doing this?
>
> The way i see it is a couple of master cylinders
> (ebay it), a balance bar, and some fabbing on my
> end.
>
> How much better are these brakes going to be with
> a dual master set-up? I know the Calipers are not
> blingy stuff, but the front cast iron puppies do
> work just fine, and the rears are alloy (which get
> worn away), but they should work just fine as
> well. They are also a dime a dozen, along with
> the rotors.
>
>
> What size masters should a person be using?
>
> And how come everyone else running this set-up is
> not having problems? Theres lots of others using
> this stuff.

I did exactly what you describe. It was a pain in tha ass to get it right and make it fit up under the dash. I also modified the pedal ratio to get it as close to 6:1 as I could.
I've tried different MC sizes, but I tinhk I have 5/8" on both now.. I can check.


Next time I'll spend the extra money and get a floor mount pedal set. Something like this...
http://cgi.ebay.com/ebaymotors/Tilton-Engineering-72680-Pedal-Assembly-Floor-Mount-_W0QQcmdZViewItemQQhashZitem4cf01fdcc2QQitemZ330446134466QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

-Martin.

Do It Sidewayz Wrote:
-------------------------------------------------------
> I guess i can measure tonight.
>
> Well. not really dime a dozen, but they are
> available from the dealer new for like $200 each.
>
> The rotors are easily found, and pads are the same
> as a 300zx Nissan.
>
> Chris

OOOOOooooooooOOOOOOOHHH!
FUCKIN $200 EACH!!!!

My fuckin GAWD, SON.
Are we talking about the same dime a dozen REAR CALIPERS?????

$200 buckskis!!!!! is a dime a dozen?

Man I knew you Canajioans were rolling in dough!
I KNEW it!

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

$200, New OEM from the dealer....

You can get them cheaper from JDM guys, and boy racer types.

---

Chris

Martin,

I think you are using basically the same Calipers i've got.

The Nissan things are very similar to the Subaru things, just different rotor sizes.

Did you notice a big difference?

---

Chris

Way back in the dark ages...I couldn't get enough rear brake on my Datsun 210/510s using stock front discs and rear 200SX discs. We didn't have all the pad options available today. Pre-internet so I somehow figured out that I could put a prop valve from the back of a Toyota PU in the car with a home made adjuster. That is the valve that is mounted on the truck frame and adjusts brake pressure according to load. It actually transfers the pressure to the other end. I think I put it in backwards so it cut down the front pressure and transfered it to the rears. Scarey at best.

Nowadays I think it would be way better to have John set something up for me....

So what's best?

a $4, Union fitting to delete the Prop valve?

Or....scrap it all and try and work in dual masters, or graft in a Tilton Firewall Mounted Pedal box?

Friends are running the same set-up with a dual banjo coming off the same fitting on the brake master. One to the front brakes, one to the rear....it seems ok, but i've never driven the car.

---

Chris

Just put more aggressive rear pads, its the easiest thing you can do. What do you even have on there right now?

I'm running some EBC race pads, which are not quite on the market yet.

I haven't had them fade on the track or other wise, and i can't complain for the price. They have been great so far, and would be even better if i could get the rears to work better/at all.

---

Chris