Do I need a proportioning valve?

DaveBishop · Post by **DaveBishop** » Wed Sep 25, 13 1:03 pm

Hi Pete when you used to get rebuild kits that is what the instructions told you to do. They supplied a new one in the kit you only put them back when you had drums. I remember doing this years ago when I changed to discs on the front

db · Post by db » Wed Sep 25, 13 2:18 pm

Here's mine- I mounted it on my chassis.
It pokes out under the drivers seat, I can adjust when I'm driving if it starts raining

Dave-R · Post by **Dave-R** » Wed Sep 25, 13 3:43 pm

db wrote:Here's mine- I mounted it on my chassis.
It pokes out under the drivers seat, I can adjust when I'm driving if it starts raining

I think you might leak fluid without longer brake pipes on that installation Paul.

db · Post by db » Wed Sep 25, 13 9:29 pm

GTXJim · Post by **GTXJim** » Thu Sep 26, 13 7:46 am

Easy to bleed though.......

Hemimad · Post by **Hemimad** » Wed Nov 27, 13 10:39 pm

Cheers for the advice on this, thought a little update on the result, seeing that I have just fitted the MC. Tried to obtain a manual disc MC only to draw a blank other than for A Body's, so decided to remove the valve from my new MC using the method suggested by DaveB, practiced on my old MC, withdrew the valve and spring no problem. Struggled a bit on the new one and damaged the seat, however no valve or spring present after all the effort!! Used the good seat from my old MC to repair the new MC, job done but wasted 2 hours achieving very little.

Thanks too all, as I would have merrily of fitted the Wilwood discs not knowing about the RP valve and the pads could of bound leaving a lot of head scratching!!!

Blue · Post by **Blue** » Thu Nov 28, 13 7:48 am

Pretty sure I read somewhere that drum wheel cylinders no longer use that type of seal?

Dave999 · Post by **Dave999** » Thu Nov 28, 13 9:09 am

given that mopar was still using the same drum slaves on the dakota pickups in the 1990s there are a huge range of different Bores of drum brake slave cylinders

now this would be useful if i could rember if you went bigger or smaller to reduce rear braking

but i can't remeber

what i do know is disk brake cars had different rear cylinders

i also know a narrower master cylinder reduces peddle effort but increases peddle movemnet to give feel

a big fat one increases peddle effort but shifts so much brake juice you only have to move it a smidge

the reveres will be the case at the other end i think but can not confirm

the one thing to remeber is presure is the same in all places in a sealed system

the force exerted by a pressure is dicated by the surface area it acts on
which is why drawing pins work

no head on the pin and it would stick in ya finger etc

so am guessing

ignore the above i just found this

most cars rolled out of the assembly plant with less-than-ideal proportioning, characterized by a tendency toward early rear-wheel lockup.

There are other ways to alter front/rear balance. One way, which reduces rear lockup, is to use a 7/8-inch rear wheel cylinder in place of the standard 15/16-inch unit. Try Raybestos part number WC37236 for this. (Original application: late ‘70-early ‘80s light-duty Dodge trucks w/10-in. rear drums).

Dave

Pete · Post by **Pete** » Thu Nov 28, 13 9:59 am

My 200 Durango has rear drum brakes..

jerry · Post by **jerry** » Thu Nov 28, 13 5:30 pm

Blue wrote:Pretty sure I read somewhere that drum wheel cylinders no longer use that type of seal?

Read that to only last week

morgan · Post by **morgan** » Thu Nov 28, 13 9:03 pm

yeah. Gotta do mine... Always locked the rears up first ( kinda cool, kinda scary - looks great pulling up at the lights slighty diagonally

) - thought my lovely new front kit would give me a bit more power, but rears still go first.
Was intending to run it up through the floor or under bonnet...

MrNorm · Post by **MrNorm** » Fri Nov 29, 13 11:55 am

Blue wrote:Pretty sure I read somewhere that drum wheel cylinders no longer use that type of seal?

Yes, EBerg has said that for one...

Anyway here is my adjustable valve - I also decided to put it under the seat, though agree with Dave, in most cases it will be adjusted once and never again!

Pete · Post by **Pete** » Thu Dec 19, 13 10:57 pm

Blue wrote:Pretty sure I read somewhere that drum wheel cylinders no longer use that type of seal?

Well, I just changed the Dart to Wilwood disc brakes and took a punt that the original (Drum) M/C would cut the mustard.

Unfortunately, as soon as the Brakes were bled the discs were binding.
Bugger.

It is a shame as the pedal pressure and feel was great.

Does anyone has a spare seat that I could have in the hope that I could remove the existing one and take out the shuttle valve behind it?

Alternatively, I did wonder about running a very small drill down the orifice to destroy the return valve - lazy, ehhh??

Thanks in anticipation.

Cheers!!!

Dave-R · Post by **Dave-R** » Sat Apr 05, 14 8:17 pm

How did you get on with that Pete?

I ask because I am looking at a car for a mate and the front discs are binding. He still has the 1960s drum brake MC so I suspect I need to remove that darn valve.

Pete · Post by **Pete** » Sat Apr 05, 14 8:41 pm

I had to remove the seat in the Master cylinder by using a coarse threaded screw and a pair of flat-bladed screwdrivers to lever it out.

I removed the small shuttle valve and spring that is located behind the brass seat.

We then cleaned up the brass seat on a lathe and re-inserted it using the pipe retaining fitting to ensure the seat went in parallel to the outlet bore and bottomed out correctly.

You could clean up the seat with a file and crocus paper....

It all bolted up fine and re-bled OK (no M/C bench bleeding required) and it was immediately apparent that the Discs were then working correctly.

Much cheaper than a new Master Cylinder, you just need to be careful and go for it.

I think the main trick is not to insert the screw too shallow as it will pull out and cause more damage; you have to accept that you WILL damage the seat - the trick is not damaging it too much so that the brake pipe still seats OK with no loss of fluid.