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proportioning valve + rear disk swap (WTB: valve)


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31 replies to this topic

#1 belacane

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Posted 14 October 2012 - 09:24 AM

So I'm planning on doing a rear disk swap on my '86 Brat and I don't have the proportioning valve off the donor car (it's somewhere in Utah).

I've heard various opinion on whether or not it's necessary for the swap, but I think I'd like to have it if possible (if I understand the downside to not having it correctly).

However, I'm not sure what it even looks like, much less how/where it connects into the brake lines so I can replicate it.

So I have a few main questions (in no particular order):

1) does anyone happen to have access to an XT proportioning valve? There aren't any in junk yards in my area.

2) does anyone have any PHOTOS / DIAGRAMS of how the valve hooks up so I can replicate it?

3) would an aftermarket valve such as this one work?


Thanks in advance!
best wishes :)

Edited by belacane, 14 October 2012 - 09:28 AM.


#2 edrach

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Posted 14 October 2012 - 09:31 AM

I'm one of those who's done at least 4 of the rear disk swaps and never added/replaced a proportioning valve. I've never seen the need for one. However, there are some on the Board with more experience than I who insist it's needed for safety reasons. Listen to both sides and decide what you need to do. If someone can post a pic and a location, I'd be glad to try and pull one for you at our local pull a part yards. But I'm in the same boat as you are...I have no clue what it looks like or where in the car to find one.

#3 TomRhere

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Posted 14 October 2012 - 11:52 AM

I have the PV out of the XT6 that I had. Yours if you want it.

I can print a page out of the FSM that shows the whole brake system.
Can aslo include the text that explains the system and how it all works.

PM me your street addy.

edit;

I was under the impression that you "had" the donor vehicle, not that you just have the disc parts.

#4 Gloyale

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Posted 14 October 2012 - 12:28 PM

You could also use one from another vehichle.

Legacies, the valve is mounted up in the engine bay, on the passenger strut tower.

it bassically just has 2 lines in, and 2 lines out.....you can add it in the lines anywhere. It doesn't have to be just like the EA setup.

#5 belacane

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Posted 14 October 2012 - 03:29 PM

cool thanks! PMed you.
Also, which manual do you have? I have the fsm from '83, but I couldn't find anything about the PV in it. Maybe I just overlooked it.

I have the PV out of the XT6 that I had. Yours if you want it.

I can print a page out of the FSM that shows the whole brake system.
Can aslo include the text that explains the system and how it all works.

PM me your street addy.

edit;

I was under the impression that you "had" the donor vehicle, not that you just have the disc parts.



#6 Numbchux

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Posted 14 October 2012 - 04:43 PM

I'm under the impression that EA81s don't have one at all. The brake balance was achieved by [mis]matching the brake setups accordingly. The posts I've seen on this subject only refer to doing this in EA81s, and that an EA82 valve (even if it had drums) is just fine.

The rear brakes on a subaru are on 2 separate systems, so if you wanted to use a universal one like that, you'd either need 2, or you'd need to completely replumb the system.


Stock EA82 valve is mounted in front of the rear suspension (not far from the fuel pump), and has 4 brake lines going to it. It's not hard to find.





I have a rear disc swap on my brat without the valve. BUT, I have never driven it on the road, at speed, or locked up the brakes. So I cannot speak from experience on that.

But, if the rears really do lock up first, that can be a very dangerous situation. A very small fraction of drivers can INSTINCTUALLY recover from oversteer. Thanks to 100s of hours of ice racing, I do believe I am in that group. But if you have to think about what you need to do to gather the vehicle up and get it going where you want it to go, it's too late.

#7 Idasho

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Posted 14 October 2012 - 07:05 PM

I'm under the impression that EA81s don't have one at all. The brake balance was achieved by [mis]matching the brake setups accordingly.


Thats correct.

The front-rear adjustment is done via the back drums.

The front discs are self-adjusting.

The adjustment comes with setting the play between the drum and the brake shoe. Adjusted out the rear brakes work less, engaging later, tighten the gap between shoe and drum and the rears do more, engaging sooner.


Ill also say that it can be VERY dangerous to put rear discs (which are self-adjusting) on a rig without the use of a proportioning valve. Engaging the rears too early is a bad, bad thing. Front brakes are designed to do a majority of the braking.

#8 TOONGA

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Posted 14 October 2012 - 07:25 PM

I have a rear disc set up on my Brumby and I don't know if we get a proportioning valve from the factory. I have never had a problem with the brakes since I put the discs on, in fact my ute actually stops now :)

TOONGA

#9 monstaru

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Posted 14 October 2012 - 07:34 PM

I drove my Brat all over the NW with no prop. valve.And let it just be said that I drive my rigs pretty hard,and NEVER, I meanNEVER had an issue with brakeing....

Also never used one on Lilly, and have helped install at least three others that didna use it.......
cheers

#10 Crazyeights

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Posted 14 October 2012 - 07:35 PM

Great info, Thanks

#11 belacane

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Posted 14 October 2012 - 08:15 PM

Ill also say that it can be VERY dangerous to put rear discs (which are self-adjusting) on a rig without the use of a proportioning valve. Engaging the rears too early is a bad, bad thing. Front brakes are designed to do a majority of the braking.


This is what my impression was to.
I want to put the valve on, just unsure of how to do so.
Hopefully the pages from the manual that tomrhere is sending over will help, but if anyone else has photos or suggestions, I'm more than happy to hear them!

#12 TomRhere

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Posted 15 October 2012 - 02:32 AM

The FSM I spoke of is for the XT6.

I'll get the info printed off, get the PV and info in a box later today.

Let you know when it's on it's way.

#13 el_freddo

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Posted 15 October 2012 - 02:49 AM

an EA82 valve (even if it had drums) is just fine.


This is what I've heard and worked with too. The rear discs on the L series is a simple swap of the hardware from drums to discs.

I have a rear disc set up on my Brumby and I don't know if we get a proportioning valve from the factory. I have never had a problem with the brakes since I put the discs on, in fact my ute actually stops now :)


Yeah I don't know Toonga about our brumbys and a proportioning valve. But I've seen many forum members swap to rear discs on the MYs and brumbys without a rear lock up issue. Time to go look at Sunnie the Brumby (who's still living at mine :D)

Cheers

Bennie

#14 LPGsuperchargedBrumby

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Posted 15 October 2012 - 03:10 AM

i've had a rear disc setup from a EA82 on my brumby and now have a XT6 setup on it....neither have had a proportion valve and i have never had a problem with the rears locking up prematurely

#15 belacane

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Posted 16 October 2012 - 11:23 AM

The FSM I spoke of is for the XT6.

I'll get the info printed off, get the PV and info in a box later today.

Let you know when it's on it's way.


Thanks so much Tom! You are awesone!

#16 TomRhere

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Posted 16 October 2012 - 06:20 PM

Printer is refusing to coperate with any computer in this here house. Must be time for a new one..
PM me your email addy and I'll send that section of the XT6 FSM.

PV will be sent your way tomorrow via UPS. Let you know shipping.

Think you can convince the Wife about that "awesome" part for me? :brow:

edit;

Is that St., Ave., Dr., for your street addy. I know they'll ask me about it.

Edited by TomRhere, 16 October 2012 - 06:45 PM.
Question added


#17 Numbchux

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Posted 16 October 2012 - 09:11 PM

'88 XT service manuals:
http://www.numbchuxc...T_Section_1.zip
http://www.numbchuxc...Section_2&3.zip
http://www.numbchuxc...Section_4&5.zip
http://www.numbchuxc...T_Section_6.zip

#18 belacane

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Posted 16 October 2012 - 09:30 PM

'88 XT service manuals:
http://www.numbchuxc...T_Section_1.zip
http://www.numbchuxc...Section_2&3.zip
http://www.numbchuxc...Section_4&5.zip
http://www.numbchuxc...T_Section_6.zip



Thanks much! A lot to sort thru :)

Edited by belacane, 16 October 2012 - 09:38 PM.


#19 ShawnW

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Posted 17 October 2012 - 12:18 AM

I certainly don't see it as a required item but nice to have for sure. The rear disc brakes are certainly less braking than the fronts-still smaller than the fronts, etc. It might be more of an issue on one with 80-82 brakes on an EA71/81 car but otherwise I dont see it being something you can lock the rear without locking the front on.

#20 BuckarooBanzai

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Posted 17 October 2012 - 01:55 AM

I certainly don't see it as a required item but nice to have for sure. The rear disc brakes are certainly less braking than the fronts-still smaller than the fronts, etc. It might be more of an issue on one with 80-82 brakes on an EA71/81 car but otherwise I dont see it being something you can lock the rear without locking the front on.


Shawn,

You also mentioned a larger disc from another EA81 model that could be used for the front disc brakes on the BRAT, was it a 84' XT Coupe?

#21 ShawnW

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Posted 17 October 2012 - 03:49 AM

Shawn,

You also mentioned a larger disc from another EA81 model that could be used for the front disc brakes on the BRAT, was it a 84' XT Coupe?


If I remember correctly it requires moving to the caliper, caliper bracket and brake rotor from an 83-87 Brat/Hatch/Wagon/Sedan or Coupe of the EA81 bodystyle. Should be a bolt in affair.

#22 belacane

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Posted 20 October 2012 - 07:51 PM

Well I now have a PV in my posession (thx to TomRHere).
It's on my list to do the swap, so I'll let everyone know how it goes.

Also had another question:

The valve is obviously off a used car and quite rusty. Is there a way to tell if the innards are still working or not?
Otherwise, I'll just install it and see what happens :clap:

#23 Crazyeights

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Posted 20 October 2012 - 07:58 PM

I would just put it on and flush some clean brake fluid through it. If it works once it's all bled out, just clean it up a little and hit it with some rust convertor or POR 15. Just be careful not to damage the rubber on the end of it.

#24 TomRhere

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Posted 21 October 2012 - 06:35 AM

Well,,, it did come off a way rusted out XT6....

Should be able to hit it with a wire brush to clean it up. Leave the cut lines attached while you do that, help keep crud out of it.

Other than disassembling it, :eek: , I don't know of any way to check it's condition prior to installing it.

#25 phantomD

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Posted 21 October 2012 - 10:40 AM

i've had a rear disc setup from a EA82 on my brumby and now have a XT6 setup on it....neither have had a proportion valve and i have never had a problem with the rears locking up prematurely


This is also my experience. The rear discs are much smaller than the fronts so a PV is not required. The braking is unbelievably improved - in fact since going rear discs I've not managed to lock up the wheels once (you can really hear the tyres working to grip the road) whereas I used to have a lot of trouble with lock up on the factory drums...




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