Proportioning Valves?

LionheartedSXT · Post by **LionheartedSXT** » Thu Sep 11, 2008 8:39 pm

Does anyone know about these on brakes? Is it true that disc brakes have smaller proportioning valves than drums systems. If this is true, would it be a problem for me switching my drums to srt-4 rear discs? Thanks in advance...

excon · Post by **excon** » Thu Sep 11, 2008 10:24 pm

i don't know, but i'm warning everyone doing the swap. know where you get your donor brakes from!

hansken_yo · Post by **hansken_yo** » Fri Sep 12, 2008 3:16 am

I don't believe there are any proportioning valves on our brake systems and you shouldn't have any problems switching from drum to disc. I was still able to achieve a firm pedal.

I did find a Brake MC that was a 15/16 bore (stock is 7/8 for SXT models) for the non-abs systems if you wanted increased fluid flow, but that isn't necessary until you start moving to larger brakes in the front.

Graphite SRT · Post by **Graphite SRT** » Fri Sep 12, 2008 9:33 am

I am pretty sure the little things that screw into the master cylinder before the brake lines are the proportioning valves. They have colored stripes on them. I read this somewhere in the FSM.

hansken_yo · Post by **hansken_yo** » Fri Sep 12, 2008 11:02 am

That would make sense... i forgot about those... there is only two.

LionheartedSXT · Post by **LionheartedSXT** » Fri Sep 12, 2008 12:13 pm

But that wouldn't affect in any way me putting the discs on then right?

hansken_yo · Post by **hansken_yo** » Fri Sep 12, 2008 12:26 pm

nope.... just that IF and only IF you change the MC like I did you will need to move them from your old one to the new one. Otherwise there is no issue.

LionheartedSXT · Post by **LionheartedSXT** » Fri Sep 12, 2008 12:52 pm

Ok good stuff, Thanks for all the help!

Hudson_Neon · Post by **Hudson_Neon** » Fri Sep 12, 2008 3:36 pm

there's a proportioning valve on ALL brake systems. they're required by law. vehicles with rear disc have a metering valve

the proportioning valve pretty much prevents the rear from locking up.

the metering valve makes it so that the brake aplication timing is perfect. disc brakes apply before drums naturally so a stock neon doesn't need one. but if you do a SRT rear disc swap, you should get the metering valve in there too. i personally didn't though. it's not that big of a deal. you just run a highter risk of the proportioning valve not doing its job and the rear locking up. my pads are wearing just fine by the way

LionheartedSXT · Post by **LionheartedSXT** » Fri Sep 12, 2008 6:26 pm

Where can I get a metering valve? and where does it need to be installed? MC or brake line area?

hansken_yo · Post by **hansken_yo** » Fri Sep 12, 2008 6:50 pm

The SRT MC is not compatible with our cars unless you go out of your way to do the whole ABS upgrade, which we all know is not really worth the $$ (see the ABS thread for what is involved). Now, with that said there was no metering valve on the MC for the SRT unless is it a part of the ABS controller, which I couldn't visually tell you one way or another.

When I ordered the MC for a base model Neon with 4 wheel disc brakes there were no additional valves that needed to be installed except for those two "proportioning valves" (if that is what they are).

So Hudson, I would like to know more of these metering valves... what they look like and where they are located as well....

Hudson_Neon · Post by **Hudson_Neon** » Sun Sep 14, 2008 8:51 pm

ok... i went into the FSM. i couldn't find anything on either the proportioning valve or metering valve under the ABS section for the SRT-4. i got to thinking that the ABS control modual probably controlls everything. turns out that i was right. on page 5-59 of the FSM it says

NOTE: Only vehicles without antilock brakes have
proportioning valves. Vehicles with antilock brakes
have electronic variable brake proportioning (EVBP)
that is built into the integrated control unit (ICU).

so if you're having problems with your brake system and you've done a "complete" SRT brake swap. make wure that you've removed your stock proportioning valve which is located off of the stock master cylinder. having the EVBP and a proportioning valve will FUBAR the system.

now as far as the rear disc comment with metering valves... aparently DCX doesn't use them. they design their systems around just the proportioning valves. now the only difference between drum and disc proportioning valves (non-ABS) is the outlet (outgoing) pressure. the drum brake proportioning valves only have 45psi less pressure on the min. and max. just a thought that as long as your stock proportioning valve is working good, it should providejust the right amount of pressure for the rear discs

thttxboy · Post by **thttxboy** » Sun Sep 14, 2008 10:37 pm

.................. hum OK proportioning valves control how much pressure is going to the rear brakes. On a car with drums the proportioning valve allows the rear drums to start just a lil bit sooner than the front when the pedal is applied so that the brakes can make contact at the same time. It takes longer for drums to start working due to the fact that they have a farther distance to travel before contact. On a car with 4 wheel disc the proportioning valve is there but it just controls pressure since we all know the front does most of the stopping it just controls how much pressure goes t the rear depending on how much pedal pressure is being applied. I have actually gone to the dealer to look up specs before i did my own and there wasnt like a huge difference in pressure which is why we dont get any issues when doin the disc swap.

OB · Post by OB » Mon Sep 15, 2008 12:26 am

^You got it right. The rear drums do indeed contact before the discs. The proportioning valve (or ABS) is usually designed to work in this fashion under light to moderated braking. When maximum pressure is asked for via foot pressure, the front will recieve pressure quicker to maximize braking power. Most vehicles operate in this manner.

hansken_yo · Post by **hansken_yo** » Mon Sep 15, 2008 8:09 pm

Hudson_Neon wrote:
so if you're having problems with your brake system and you've done a "complete" SRT brake swap. make sure that you've removed your stock proportioning valve which is located off of the stock master cylinder. having the EVBP and a proportioning valve will FUBAR the system.

This is nothing that you need to worry about because the SRT MC has only 2 ports that go directly into the ABS controller. So you cannot use the SRT MC without hooking the whole SRT ABS system together. Now the base neon MC has 4 ports and there are 2 ports in particular that require the proportioning valves in order for the brake lines to be connected.

The only real problem that can arises is the amount of flow the MC bore allows. The base neon with drum brakes has a 7/8" bore while the SRT and 2000-2002 neons with 4 wheel disc have a 15/16". You can buy a 4 wheel disc non ABS MC from Napa Auto and the part number is 390638 . This is the MC that I am currently using so that I have the upgraded flow for my Wilwoods. On the other hand it is not necessary for the standard SRT brakes, but couldn't hurt since they use a 15/16 bore for the SRT MC.