so i have completed my brake upgrade to baer 13" frt and pbr 12 " rear. my car had drum rear. what do i need to do for the prop valve. is there a stock replacement for rear disk that will work well for me ? or do i have to install a adjustable valve. i would prefer i simpler approach to flaring and bending lines for an adjustable valve.

my car is an 85 and my rear end is a 88. thanks jeff

 

What was your car in stock form...disc/drum or disc/disc? I can't remember..


Ed

 

disc /drum was stock

 

If you want the best out of your brakes then you should get an adjustable one. That is the only way you can properly balance your brake bias. Using a stock proportioning valve of any sort will never be as good as a properly setup adjustable one, doesn't matter what your brakes are. Even stock brakes can be improved by adding an adjustable valve, probably.

Si.

 

umm probally?

are you sure or no?

Jeff

 

How much you gain in braking by getting an adjustable proportioning valve over a stock one depends on how well you set it up, and how far off that setting the stock one was.

What you ideally want is all four wheels applying their maximum braking effort at the same time, and the fronts to lock just before the rears for stability. A proportioning valve simply limits the brake pressure to the rear wheels. The stock proportioning valve has to be set by GM to never lock the rears before the fronts, or they'd get sued. So to account for manufacturing variances, uneven pad/rotor/tyre wear between the front and back they will have made the stock proportioning valves very conservative. Therefore if you have good pads/rotors/tyres all round, you will find improved braking with an adjustable proportioning valve.

How much of a difference that you'll find is uncertain, and given that > 50% of the braking is done by the fronts this will further reduce the impact.

But what I would say is that given the amount of money you've spent on brakes already, you obviously want top notch performance out of your brakes, and for that you need the brake bias correctly set and that requires an adjustable proportioning valve.

Hope that made sense.....

Si.

 

I got a question if i want a adj prop valve like the wilwood one does anyone know the part number . Also since you need to reflare the lines is it setup for regular flare then and not bubble.

 

The wilwood part I went for was 260-8419. Summit sells them and some others :
http://store.summitracing.com/defaul...L%2D260%2D8419

The fittings into the wilwood prop valve are 3/8"UNF Short fittings with regular double flares. The wilwood valve actually has 1/8NPT but comes with the port adapters to get the 3/8"UNF fitting.

Now when I say 3/8"UNF short fitting I would just like to flag this as a possible problem, though it might not be an issue in the USA. Basically the fittings into the adaptors have very short depth of thread, and where the common type of fitting in the UK has a 1/8" long section on non threaded material at the very end, this doesn't work due to the short length of the threaded section. I had to get fittings with thread almost to the end of the fitting. I think this may be more common in the USA but it was expensive to get the fittings in the UK.

Hope that made some sense.... as I don't have any pictures of it to hand.

Si.

 

It doesnt look like that one in the picture does it.

 

If you mean does the 3/8"UNF short fittings look like the ones in the wilwood proportioning valve picture then yes kinda, since they require the thread up to the end like those wilwood adapters.

Si.

 

No i meant the valve dont look like the one in the picture dont have enough hook ups.

 

A simple solution is to install a 1LE prop valve. The Bear caliper is pretty much the same as a 1LE (same piston size). Also the 1LE used the same master cylinder as the disc / drum setup.

 

I have the 1LE valve if anyone wants to buy it. I rather be able to adjust it myself .

 

Spdfrk1990: Okay, I think you really should put a bit more in the way of words into what you're saying as you cause confusion.....

The issue you have is that what you are calling the proportioning valve is also known as the combination valve, this is because it also has the T piece for the front brakes, and also a pressure fail sensor, as well as the proportioning valve for the rear brakes.

Have you read the technical article about fitting an adjustable proportioning valve?
https://www.thirdgen.org/newdesign/tech/propvalve.shtml

There are 2 ways to fit the proportioning valve : gut the existing one and add the wilwood part, or use a T piece for the fronts. I did the later, as I've heard some people have trouble resealing the gutted stock combination valve. Down side is that you lose the brake fail sensor, but my thoughts on that are that the instant the warning light would come on, you already know the brakes down work as you pushed the pedal and nowt happened!!!!

Back to the main question : You've just spent $1k+ on upgrading brakes, why not finish the job properly?

Si. :lala:

 

I thought we were talking about the prop valve here whats so hard about that to understand. Anyway i wanted one to replace the stock one not still have to use it or gut it.

 

As I stated the stock "proportioning valve" is more than just that. In one lump of metal it has a proportiong valve, pressure sensor, and T piece. If you want an adjustable one you have to get the other bits separately.

Si.

 

Alright ill check out the article i really dont care about the light though no big deal.

 

Alright, here's some thoughts from someone who gone through both ways of thje equation...

First car that i swapped a 12" pbr disk rear into (disk front, drum rear originally) - I eliminated all the stock proportioning valve stuff and made new lines. (or modded the ones there, was a while ago) and yes, you will get good at double flairing lines in a tight spot! I installed an adjusatble valve for the rears and went direct off the master cyl to the fronts through a "T".

Notes:
Worked great, but i ended up just turning it on full open - never EVER had the rears lock up on me first. Infact i had to get into it so hard to get the rears to lock, the fronts were locked to hell at that point lol....

Second car (and my current one) Same swap rear end swap, left the proportioning valve and all that stuff alone, completely 100% stock.

Notes:
Stops just as well, although i have huge rears on this car (335's) so i doubt i will ever lock them up with the brakes...


The only issue i think you will have that would make it necesary for you to do an install like what i did on the first car, is the fact that you messed with the front brakes! You have a lot more FRONT stopping power availiable now, which is gonna make less pedal necesary to get the fronts working, which in turn is going to make less pressure go to the rears. Basically, your stock proportioning valve is going to put too much braking power on the front due to the extra friction surface.

My recommendation - yank all that **** out and do what i did with my first car - direct off the master cyl to a "T" for the fronts, and direct off the MC to an adjustable proportioning valve and back...

 

lots of good info anyone else have an idea on which is best..

Jeff

 

The 1LE prop valve will do the job without all of the guess work required with an adjustable.

 

i would prefer a swap prop valve i have a new adjustable that came with the kit but it may be overkill for a occasional driver. what years did the 1le come on. anyone know what the part # is to order from gm i guess would be the likely source.

thanks Jeff

 

Sure...it's all listed here:

http://www.ws6transam.org/1LEbrake.html


Ed

 

Plumb it so that the adjustable prop is inside the car.

 

I have a similar question. A freinds car came with rear disks ('87 TA), and the hardware was in serious need of rebuild. He swapped in a rear with drum brakes untill we can get the disk set up rebuilt. He has a drum prop vale that was picked up at a salvage yard but the threads in the valve are either different (fine/course) or they are damaged. Both valves are stock GM issue. Can you swap the valve guts from the drum valve to the existing disk valve? Are the blocks the same? Might save us some time and money.

Thanks

 

If I go with an adjustable prop valve, where can I get a T-block for the front brake lines. Can you just by pass the stock block with the rear lines going to the adj valve?