rear disc proportioning valve?

[Robend]

i dont remember if this was ever discussed on the old forum or not, but do we need the proportioning valve for rear disc if we do a swap? i can't seem to find out if they're the same part number or not.

[mellowness65]

it's not necessary to the swap, but it is different in rear discs

[Canuck]

Good luck getting one... Ford does sell them, but they are only sold with master cylinder... $$$

[Thnikkaman]

I did find a part number from ford for only the proportion valves, they were about $200 for the ones from a S/R... and you would need 2 of them! i spent less than that on my whole swap.

Grab the ones out of the 2nd gen escort you get the brakes from and swap them in. make sure you grab ABS ones if you have ABS and non-abs if you dont have ABS.

Disc brakes need more pressure than drums so you wont get the full potential of your braking system unless you swap the valves.

I've also thought of aftermarket proportioning valves. the problem is you would need one in each of the rear lines or you would need to re-plumb the brake system to remove the double diagonal split. i really didn't like the prospect of either option.

[ZX2WV]

i do have the MC/PV from the S/R i got my rear disc's from just sittin in the garage. i was just too lazy to put it in. haha.

[Thnikkaman]

want to sell it to me? lol

[Robend]

well, i know the rear valve under the rear crossmember (i wanna call it that) is a distribution valve, and we already have that on our car. mines not ABS and i, very inclined to say that due to the rear distribution valve its not a diagonal split braking system. wouldn't i only need the one that comes off the master cylinder? if mech could get in on this

[ZX2R]

I did find a part number from ford for only the proportion valves, they were about $200 for the ones from a S/R... and you would need 2 of them! i spent less than that on my whole swap.

Grab the ones out of the 2nd gen escort you get the brakes from and swap them in. make sure you grab ABS ones if you have ABS and non-abs if you dont have ABS.

Disc brakes need more pressure than drums so you wont get the full potential of your braking system unless you swap the valves.

I've also thought of aftermarket proportioning valves. the problem is you would need one in each of the rear lines or you would need to re-plumb the brake system to remove the double diagonal split. i really didn't like the prospect of either option.
You only need the one proportioning valve that is attached to the master cylinder.

[mechtech]

The proportioning valve limits the pressure to the rear wheels so they won't lock up. This varies with speed, so unless you have a variable one like in a VW rabbit it will be a compromise.
Rear drum systems have a one way valve to keep a few pounds of pressure in the system, so the brakes will activate quickly when needed. This is balanced by the brake return springs.
This is one reason I wouild never consider a rear disc swap in my ZX2.

[ZX2WV]

want to sell it to me? lol

if you want it. lol

[mellowness65]

did second gens have the valves? An automatic LX-E at the jy with rear discs didn't

[iceracer]

Mech brought up a good point. The drums have a residual pressure while the discs do not.
The conection block on the rear cross member is just that. It has two lines going in and two going out. We do have diagonal braking. The block is not a valve of an sort.

[Robend]

ok so we are diagonally split, therefor we need two proportioning valves. so can we just take them off of the master cylinder on the escort gt we're pulling the rear discs off of?

i looked up both master cylinders on autozone.com... they're the same part number for a 2000 zx2 as they are for a 96 escort. would it be fair to assume that the proportioning valves for the escort gt would fit in our master cylinder and work correctly?

[Canuck]

They will fit. Someone sent me a proportioning valve from and older escort and it fit just fine.

[sadcat]

The proportioning valves for a Non ABS car are located on the bottom of the master cylinder. ABS proportioning valves are located on the firewall. Look on the end of the proportioning valve. It will be stamped with a "2" or a "4". The ones stamped with a "2" are for drum brakes. While the ones stamped with a "4" are for disc brakes. So the typical ZX2 with disc-drum brakes will have one of each proportioning valves.
The master cylinders used in the ZX2 were
1. Disc-Drum MTX No ABS (has a residual pressure valve for rear Drums)
2. Disc-Drum ATX No ABS (same as the MTX but without the clutch port in the reservoir)
3. Disc-Disc MTX No ABS (no residual pressure valve installed)
4. Disc-Disc ATX No ABS (same as the MTX but without the clutch port in the reservoir)
5. ABS MTX (the Disc-Drum and Disc-Disc are the same and have no residual pressure valve installed)
6. ABS ATX (same as the MTX but without the clutch port in the reservoir)

[mechtech]

Sadcat - You rock!

[iceracer]

Excellant !

[Robend]

thank you

[BernardZX2]

Is it possible to put the proportioning valve on the front brakes?

[sadcat]

Is it possible to put the proportioning valve on the front brakes?

All of the ZX2s have 2 proportioning valves. 1 for the front brakes, and 1 for the rear brakes.
So the typical ZX2 with front discs and rear drums will have a proportioning valve with the number 4 stamped on it for the front discs. It will also have a proportioning valve with the number 2 stamped on it for the rear drums.

A ZX2 with front and rear discs will have a proportioning valve with the number 4 stamped on it for the front discs. It will also have a proportioning valve with the number 4 stamped on it for the rear discs.

[Thnikkaman]

the two proportioning valves on the zx2 are on the rear lines only. If you trace the lines, one goes from the master cylinder to the right front brake, one to the left front brake. one comes from a proportioning valve to the left rear brake and one from a proportioning valve to the right rear brake. This is for a non-ABS car.

number '6' on this diagram points to the proportioning valves, they are in the rear lines only. the front lines have no pressure control devices.

[Thnikkaman]

Is it possible to put the proportioning valve on the front brakes?

you wouldn't want to. Proportioning valves reduce the pressure in the line. The front brakes are responsible for the majority of the braking so you wouldn't want to reduce that. The reason we need them on the rear brakes is they will lock up fast since the majority of the cars weight is transferred to the fronts when braking. the valves reduce the pressure to the rear brakes preventing them from locking up before the fronts.

[Thnikkaman]

sorry to resurrect a dead post but i wanted to add a little more information. recently i attempted to swap over to rear proportioning valves from a junkyard 2nd gen escort sedan with rear discs. The valves had a different bolt diameter and thread pitch and would not thread into the zx2 master cylinder. if you want to replace the proportioning valves, you have to grab a whole master cylinder assembly.

[DaviDawg]

awesome, thanks for the info.

[zxtwou2]

i have my stock mtx disc-drum hardware..and have done the rear disc swap from an EGT. under daily driving, i have no issues whatsoever. in autoX..i have to find a happy place in the brakes in order not to lock up the FRONT brakes. the rear ones have yet to lock up on me, even at HARD braking.

[Thnikkaman]

i have my stock mtx disc-drum hardware..and have done the rear disc swap from an EGT. under daily driving, i have no issues whatsoever. in autoX..i have to find a happy place in the brakes in order not to lock up the FRONT brakes. the rear ones have yet to lock up on me, even at HARD braking.

this is exactly why i want to replace the proportioning valves. you want your front and rears to lock up at the same time. right now, your rear discs are underachieving! more pressure back there will help the car brake faster.

[JohnP]

If the rear calipers are adjusted correctly they will lock up in a panic stop , been there a few times , stops on a dime and you get change.

[BernardZX2]

The master cylinders used in the ZX2 were
1. Disc-Drum MTX No ABS (has a residual pressure valve for rear Drums)
2. Disc-Drum ATX No ABS (same as the MTX but without the clutch port in the reservoir)
3. Disc-Disc MTX No ABS (no residual pressure valve installed)
4. Disc-Disc ATX No ABS (same as the MTX but without the clutch port in the reservoir)
5. ABS MTX (the Disc-Drum and Disc-Disc are the same and have no residual pressure valve installed)
6. ABS ATX (same as the MTX but without the clutch port in the reservoir)

Where is this pressure valve and can it be removed/replaced?