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ferguson777 10-17-2005 08:09 AM

Volare proportioning valve?
I am in the midst of installing my brake lines. I had raised a question in the later model F150 forum asking for details on which inlets/outlets on the 1990 F150 RABS valve go where. I had been assuming the RABS valve performed the proportioning valve function. Now Iím thinking it does not.

So this raises some questions;

If itís not performing the function of a proportioning valve, then where is the proportioning valve? Is it in the master cylinder? Iím using an 84 Chrysler 5th Ave. master cylinder with the Chrysler front disc brakes and 72 Mustang rear drum brakes. Is it (proportioning valve functionality) in the master cylinder? Or is it a physically seperate entity?

And since my 72 Mustang rear end does not have RABS functionality, then this would render use of the RABS valve totally unnecessary, right?



AXracer 10-17-2005 08:17 AM

If you are talking the Canuk speak for antilock brakes, it's near impossible to retrofit ABS (requires sensors on each wheel and a computer to sort out the sgnals).
Was the MC one that was used on a drum/disc setup originally? if not you'll need a proportioning valve. (some MC have them built in) You can recognize a disc/drum MC because the front chamber will be significantly larger than the rear.

Brian_B 10-17-2005 08:40 AM

RABS...older ford speak for rear antilock brakes. The RABS systems I have worked on had a tone ring in the rear axle beside the ring and pinion. ABS uses the wheel speed sensors on the newer ones.

I know nothing about a proportioning valve. I thought the two seperate areas in the master cylinder eliminated a need for it. Oh...he just explained that part. I can't read. :-wink

ferguson777 10-17-2005 10:06 AM

Certainly my day for working everybody's brains........

Yah - RABS apparently stands for Rear Anti Braking System. It works with the computer and a sensor in the rear end. The rear end I'm using does not have said sensor and I do not want to utilize any sort of ABS or RABS system.

I simply want to determine that I do/do not have a proportioning valve.

The master cylinder I'm using is from an 84 Mopar 5th Ave. (Same donor as my front suspension and brakes) The mstr cyl. is the dual ressevior type and worked with front discs and rear drums. So do any of you Volare equipped dudes know for certain if the proportioning valve is built into the master cylinder?


merc546 10-17-2005 10:47 AM

The haynes book that I'm looking at just shows a aluminum M/C for your year (that they say is not rebuildable at home?) anyway it looks like there isn't any internal prop valve.

I have a Volare frt with a 9 inch drum rear and a booster and pedal from a 7? torino (spelling) I'm guessing that the prop valve came form the same vehicle. I bought the truck with this susp and brake arrangement it's worked for over 15 yrs so I just cleaned it up a bit. Hope this helps

AXracer 10-17-2005 12:02 PM

MP brakes are the experts in hot rod brakes, I'd ask them about your MC. My opinion is that if your Volare MC was being used for disc/drum application and there was no separate proportioning valve ( usually a brass block ~ 1.5x4x .75" with several lines going in and out, then the prportioning valve is built in. Most OEM manufacturers that I'm familiar with that use them, mount an external poportioning valve along side or below the MC attached to the MC or it's mount, in which case it would have likely come with the used MC. You still may need to use an adjustable PV in one of the lines to fine adjust the brake bias since you are mixing manufacturers and brake sizes as well as weight distribution. My suggestion is to hook it up as is and try it. Do several 20 MPH panic stops in a large parking lot and see how the truck reacts. If it brakes in a straight line without steering input, locking up all 4 wheels at near the same time (check skid marks) you're good to go. If not, i.e. one end locks up well in advance of the other, or one doesn't lock up at all, or the truck tries to swap ends then you'll need to adjust the bias with a proportioning valve, or by changing pad/shoe sizes or composition.

fatfenders 10-17-2005 12:51 PM


I believe you probably DO need to run a proportioning valve with that MC. The Volare setups I have seen were running a separate PV. Not that I've seen them all of course wth the wide application of the V-clip. I've seen a lot of PV mounted on the frame rail. Could you have missed it? I forgot if you pulled the clip yourself or not.

If using salvage parts, matching up the MC and PP from the same vehicle seems the prudent way to go of course. I am using later model Ford truck MC and PV and it works very well. Not that it helps you any.

ferguson777 10-17-2005 01:41 PM

Ax & 'fenders,

Yah, I pulled my own front K member and the master cylinder and pedal assy. Can't remember if there was a seperate proportioning/metering/combination valve on the beast or not. Thought I was being real smart by grabbing (what I thought) was the proportioing valve off the F150 that donated my drivetrain but it turns out to be a RABS valve......

That MPBrakes site was quite interesting. Guess I'll grab a combination valve from them and be done with it..........



fatfenders 10-17-2005 04:14 PM

"That MPBrakes site was quite interesting. Guess I'll grab a combination valve from them and be done with it.........."


If you're talking about an adjustable PV, that would be the way to fly anyway IMO. You can really dial it in perfect, and make subsequent adjustments as you jack and re-jack with the rest of the truck over time.

ferguson777 10-17-2005 05:04 PM

I've been able to determine that the Mopar 5th Ave master cylinder definitely does NOT have proportioning functionality built in to it. The proportioning valve is a seperate entity............

To bad the RABS valve doesn't have it also. It even looks like one........ :mad:


GreatNorthWoods 10-18-2005 05:24 AM


I'm using an 87 Chrysler 5th Avenue MC and stock combination valve on my 48 F-3. The valve is definitely a separate item. I removed it from the donor vehicle when I removed the MC and brake booster. I have plumbed the brake lines and bled the system but I have not driven the truck yet. I'd be interested to know if anyone has used this brake system and left the valve out. It was a PITA to plumb it into the system and considered omitting it but I was afraid the brakes would not work right without it. :)


ferguson777 10-18-2005 05:52 AM

I'm off to a wrecker this saturday for another reason, maybe I'll try and snag a used one while I'm there.........


vanHoy 10-18-2005 10:01 AM

You're on the wrong forum for Volare brakes. Try a Chrysler forum. [I'm on those too for my old DeSotos Dodge and Plymouths]. There's no proportioning valve in the Chrysler's master cylinder.

You may not want to use the proportioning valve from a junk Volare because... it's set up for a Volare. Too many variables. Your braking characteristics on an old Ford truck will be very different. The Mustang rears are different than the Bendix on the Volare. Et cetera.

Most of the guys recommend an adjustable proportioning valve.


GreatNorthWoods 10-18-2005 10:28 AM


I highly doubt going to a Chrysler forum would be of more help regarding the use of Mopar brakes in a Ford truck than here. That would be about like going to a Chrysler forum and asking about using a Volare suspension in a Ford truck. There are probably more Chrysler T-bar and Volare suspension users here than anywhere else and we would be in a better position to report on that than a Chrysler group where the suspension is still in the original car. It's just not the same. :)

I do, however, think you have a valid point about the variables. I'm hoping that since I used the Chrysler rear end and that my truck will be about the same weight as the 87 5th Avenue I pulled the brake system from, the brakes will behave as they did in the Chrysler. I realize the weight distribution will be different on a truck with a lot more weight on the front end than the rear, but since the front brakes do about 70% of the stopping anyway, I'm thinking it will work fine. When I get my old truck drivable I will report back here on this... :)


fatfenders 10-18-2005 11:40 AM


Adjustable PV would be nice if you have the money, but I suspect you'll be just fine too. I have heard of people running all sorts of combos of front and rear brakes. Masters and PVs off Mustangs, Econolines, Volares, You name it. I was skeptical, but don't recall anyone saying it didn't work out for them. I think the only big mistakes you could make is mixing power and manual brake components, or mixing disk and drum (i.e. Front disc MC & 4 wheel drum brake combo, or vice-versa)

Just take AX advice no matter what route you take so you don't find out the tail end comes around in an emerency stop. Test your brakes like you would if you just did major brake work. That's just common sense for all the mods we rodders make.

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