More rear disc swap questions

[mellow65]

Ok so I was out at the junkyard and snagged me a full set of rear discs from a wagon with brand new pads. WOO HOO:headbang: And thank god for the new guy at the counter, they never seem to charge you for it all. $30 out the door. So my question is where is that damn proportioning valve? I was strapped for time, the yard was closing and I had 15 min to yank all I could.

 

I did a quick look and tried to follow the lines, I found the ones going to the front but then it seems the line going to the rear went inside the cab. Is it under the hood or out back somewhere.

 

Thanks

[GeneralDisorder]

It's under the car - follow the lines back and it's a weird looking thing inline with the hard lines comming out of the cab - it's mounted with two bolts to the "floor" where the floor of the cab rises to meet the floor of the cargo/trunk area.

 

Hope that helps.

 

On another note... what yard did you vist? - that's pretty good pricing.... I know U-Pull-It would be a lot more with the new management now.

 

GD

[mellow65]

that was U pull it, on foster, you just have to time your trips up to the counter now. The new people only ring up like half the crap and give you little things for free. The damascus one is horable, I bought the rear wind deflector off of a wagon and was trying to tell me it was a wing and wanted to charge me like $40. But at least out there you can still haggle.

[idosubaru]

this has been discussed/argued in other threads but i don't know that you need the proportining valve anyway. try searching on some other threads if you have questions about that as i'm not positive.

[GeneralDisorder]

this has been discussed/argued in other threads but i don't know that you need the proportining valve anyway. try searching on some other threads if you have questions about that as i'm not positive.

 

You do for EA81 land. EA82 is questionable.

 

GD

[mellow65]

If I can find it and it's not a pain in the rump roast to put in I'll do it. No reason not to.

[Anthenium]

I converted my EA82 to rear disk using this document:

 

http://www.ultimatesubaru.org/forum/showthread.php?t=49975

 

It says nothing about a proportioning valve for either.

 

Fat Tony - http://www.smashbandits.com

[mellow65]

I saw that one, but I have always known that 4 wheel disc brakes need a P valve. Even the drum ones have them, but I would have to figure that it is valved different. I got the right one now so all is good.

[ballitch]

i dont think you needed the prop. valve on an EA82 car. but i could be wrong, hell, i didnt change prop. valves when i went to 5 lug and rear disc. maybe thats why the car has so much front bias........i dont know.

 

 

~Josh~

[Petersubaru]

every car manufacture in the last 15 yrs installs the proportioning valve(this is not the ABS system)..it is there for Panic or Sudden hard brakeing, especially on ice and snowy conditions..to keep the car in a reasonably straight line...on some cars you would Not find them separately because the valve is built into the master cylinder...safety first

this has been discussed/argued in other threads but i don't know that you need the proportining valve anyway. try searching on some other threads if you have questions about that as i'm not positive.

[Petersubaru]

generally speaking, a P valve is a P valve...subaru I don't know but with VW, the more you pay for the car the more variables for example, changing load and height considerations are included into the P valve for optimum stopping ease

i dont think you needed the prop. valve on an EA82 car. but i could be wrong, hell, i didnt change prop. valves when i went to 5 lug and rear disc. maybe thats why the car has so much front bias........i dont know.

 

 

~Josh~

[GeneralDisorder]

generally speaking, a P valve is a P valve...

 

Totally incorrect - you can buy adjustable proportioning valves from any good race supplier. Adjusting the brake bias is very important to proper braking. You have to balance the pressure generated by the system to the size of the front and rear brakes, and their braking power, weight of the vehicle, etc. Using the correct stock valve will work for safe basic street driving though as they are already sized properly for the braking power of the rear discs.

 

GD

[Petersubaru]

You are correct within the context of "raceing" while I was referring merely to stock applications

Totally incorrect - you can buy adjustable proportioning valves from any good race supplier. Adjusting the brake bias is very important to proper braking. You have to balance the pressure generated by the system to the size of the front and rear brakes, and their braking power, weight of the vehicle, etc. Using the correct stock valve will work for safe basic street driving though as they are already sized properly for the braking power of the rear discs.

 

GD

[Qman]

Keep in mind that this is one man's opinion. Many have done this swap and had ZERO issues(other than that one man) with the brakes. The issue he had may have arisen from the fact that his wagon was originally a 2wd that he converted to 4WD.

 

Bottom line is that it has been shown to not be completely neccessary to change the proportioning valve but, by all means, if you choose to do it make sure you bleed everything completely and enjoy your new brakes!!

[GeneralDisorder]

Keep in mind that this is one man's opinion. Many have done this swap and had ZERO issues(other than that one man) with the brakes. The issue he had may have arisen from the fact that his wagon was originally a 2wd that he converted to 4WD.

 

Bottom line is that it has been shown to not be completely neccessary to change the proportioning valve but, by all means, if you choose to do it make sure you bleed everything completely and enjoy your new brakes!!

 

I have never converted my wagon, it still has drums - I converted my Brat Ken, and this "phenomenon" is not just something that I have experienced - in a recent thread two other people had the exact same symtoms. When panic braking on slick surfaces (snow, wet pavement, etc) the rear WILL lock and slide sideways without the valve. Is this so freakin hard to beleive? I'm no idiot, and I take brakes very seriously - that's why I performed the test. Next rainy day I swear I'm taking the damn valve out and rolling camera on it.

 

GD

[TheSubaruJunkie]

Just learn how to brake properly. Dont slam on your brakes and you'll be fine. Give yourself 2 car lengths between you and the car in front of you. and on ice & snow, slow down.

 

Ive coverted 3 subarus of mine. Ive never had any problems at all. Ive done some hard brake tests after replacing pads, and Ive never felt my rear end come out from me. Brakes in a straight line every time.

 

If your really anal about things, get the valve and be done with it. Like ken sais, make sure you bleed your brakes real well.

 

-Brian

[GeneralDisorder]

Just learn how to brake properly. Dont slam on your brakes and you'll be fine. Give yourself 2 car lengths between you and the car in front of you. and on ice & snow, slow down.-Brian

 

Absolutely - safe driving is key. But there are uncontrolable situations that do arise at times - people can pull out in front of you for example.

 

There is also other factors sometimes beyond your control - a vehicle that I convert may at some point be sold, or passed on to a new owner. My concience will be clear because I know I've done the job right.

 

I understand the unwillingness of people to admit they are wrong/incomplete with their previous conversions, but this is getting silly. These are BRAKES people, and safety should come first - especially here where people turn to this board for (hopefully correct) information. When I did the conversion, I first did the brakes only (85 Brat, so no valve at all). I took it up to about 50 MPH, and locked all 4 wheels on wet pavement - without the valve I had enough momentum to do a full 180 degree sweep with the back of the Brat and ended up facing the opposite direction IN the oncomming lane. I made several more attempt at lower speeds and found that I could kick the rear end out as much as I pleased based on how hard I locked the wheels, and the durration of the braking. You call that safe? I put the valve in and repeated the test (the SAME day) muliple times and could never get anything but smooth, straight braking. The ONLY difference between the two was the addition of the valve - same street, same conditions, same car. It takes about an extra hour to install the valve and the hard lines.... is that so much extra that safe braking isn't worth it??!?

 

Many of the people that have done the conversion have done it with lifted vehicles - the stock brakes are HARD to lock-up with big tires. Even fully bled and adjusted the brakes just don't lock as easily. This may be part of why it's largely gone un-noticed. That, and people don't often do panic brakeing..... I know I don't... until the day comes that you need it.

 

GD

[Petersubaru]

General..Your right on the mark...opinions are cheap and easy if you live and drive in climates where the sun nearly shines everyday, but it becomes another story when suddenly you get caught in some snow fall or ice on the road or mountain pass and only then will someone know the value and meaning of the P valve ...also it just occured to me that when driving with stock brakes (rear drum) how many out there have actually changed or replaced there old drums for new ones...once there is .080th of wear (maximum limit) across the drum coupled with near worn out shoes and maybe larger tires; well, no wonder they will not lock up or even stop effortlessly...I hope this will not lead into another thread titled "lets all go back to the Non-collapsible steering column

Absolutely - safe driving is key. But there are uncontrolable situations that do arise at times - people can pull out in front of you for example.

 

There is also other factors sometimes beyond your control - a vehicle that I convert may at some point be sold, or passed on to a new owner. My concience will be clear because I know I've done the job right.

 

I understand the unwillingness of people to admit they are wrong/incomplete with their previous conversions, but this is getting silly. These are BRAKES people, and safety should come first - especially here where people turn to this board for (hopefully correct) information. When I did the conversion, I first did the brakes only (85 Brat, so no valve at all). I took it up to about 50 MPH, and locked all 4 wheels on wet pavement - without the valve I had enough momentum to do a full 180 degree sweep with the back of the Brat and ended up facing the opposite direction IN the oncomming lane. I made several more attempt at lower speeds and found that I could kick the rear end out as much as I pleased based on how hard I locked the wheels, and the durration of the braking. You call that safe? I put the valve in and repeated the test (the SAME day) muliple times and could never get anything but smooth, straight braking. The ONLY difference between the two was the addition of the valve - same street, same conditions, same car. It takes about an extra hour to install the valve and the hard lines.... is that so much extra that safe braking isn't worth it??!?

 

Many of the people that have done the conversion have done it with lifted vehicles - the stock brakes are HARD to lock-up with big tires. Even fully bled and adjusted the brakes just don't lock as easily. This may be part of why it's largely gone un-noticed. That, and people don't often do panic brakeing..... I know I don't... until the day comes that you need it.

 

GD

[TheSubaruJunkie]

Then just get the valve and be done with it.

 

-Brian

[WoodsWagon]

WOoooo Back from the dead!

 

I have to say, on a lifted EA82, converting to disks in the rear made a real difference, I can lock up my 30" tires all round with a hard stomp, on dry pavement.

 

The EA82's came with a proportioning valve, and it seems to work well with the disks as with the drums. The back doesn't lock unless the front is too.

 

For a car without any P-valve, put one in. It's stupid not to.

[ShawnW]

I havent seen any need for the valve but to be sure I took my Brat out when I had it and had a friend watch from a safe distance. I drove down the road back toward him and slammed on the brakes as hard as I could and had him watch to see if one end locked while the other didnt or anything weird like that. He could see the brake lights come on and could watch both wheels on the left side of the car as well as could tell if the car shifted to one side weird or anything like that.

 

It might be an issue with a 1/4 set of pads in front and a new set in the rear or some weird scenerio like that but I would think in the 5-7 years that this converison has been realizied and done that somebody would have had a problem. Could also be a problem on a car with unvented in the front and disc rear.

[4x4_Welder]

Any brake system needs a proportioning valve. My truck doesn't have one due to it being drum brakes all the way around, but still the rears will lock before the fronts when it's empty.

Because the surface area of the caliper piston is so much larger than the surface area of the pistons in a wheel cylinder, it needs less pressure to achieve the same braking force. Plus, it reacts faster than a drum brake system. Combine those two issues, and it is easy to see why a straight rear disk conversion will lock up easily.

Chances are you won't notice this tendancy under normal driving conditions, but you will notice a higher, more sensative brake pedal.

If you have concern about it locking up, install a proportioning valve (Actually, two, since it's a diagonally split system), but the car won't be undriveable without this.

The tendancy to lock up will be more obvious in a Brat than in a Hatch or Wagon, due to less weight on the rear tires.

[subarubuddy]

sorry to exhume this thread out of it's grave, but i dug it up on a search and i still have a proportioning valve question:

 

i have a 92 4WD loyal wagon and i'm converting to rear discs (from some 4WD EA-82 sedan).

Being a loyale, my car came with a proportioning valve, right?

EA82's always have one? but do i need a different one (specifically for discs) or do i just leave it alone?

 

if the car should have one (or a different one), then i'd want to put it in.

if it already has the right one, problem solved.

 

the reason i ask is because the car is at my parents house 200 miles away, so i'd like to get the valve first before i go over there.

 

thanks for helping out.

 

[Turbone]

As far as I know, theres no difference with a EA82 drum brake valve and a disc brake valve. I say go for it and dont mess with it.

[Hodaka Rider]

I did the swap on my '93 Loyale. Left the stock valve in place, and have not had any problem with the rear locking before the front on dirt or pavement. You should be fine (assuming everything is in good shape).