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Old 03-15-2020, 07:13 PM   #1
Acmontreal
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Default What are ya’ll doing for rear proportioning brakes?

In my case I am running Volvo vented rotors and calipers in front and standard discs in back, but on the source vehicle the proportioning valves were toast. I can buy aftermarket manual adjust rear proportioning valves, is that what most are of you do? Or do you pay big$$ for a pair of Volvo’s rear proportioning valves? Inquiring minds want to know.
All of the above with a brake booster and 240 MC are being installed in a 120 wagon, if that helps clarify anything (probably doesn’t, all I need to know is what 240 owners are doing if not using stock proportioning valve?
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Old 03-15-2020, 07:27 PM   #2
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Run the stock ones. If you are running the dual rear split you will need two after market valves, good luck getting them both the same. I'm sure that someone has the stock valves,why reinvent the wheel?
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Old 03-15-2020, 07:33 PM   #3
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Mostly concerned as all the costs are adding up......can’t find a decent price for 2x rear proportioning valves, also the stock ones would presumably need to be adjusted as well, with O guess a set of pressure gages.....this swap has not been easy...
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Old 03-15-2020, 07:59 PM   #4
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I skip them and use a pair of front SS 240 brake lines. I have only done this while swapping to R brakes. People may tell you this is not a good idea and they may be correct, but I have no bad effects from doing this.

Alternately you could just use aftermarket valves, race cars do that all the time.
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Old 03-15-2020, 08:17 PM   #5
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Are you plumbing it for dual diagonal brakes?

My experience using adjustable proportioning valves on a dual diagonal circuit system was an inability to limit the pressure enough to keep the rear brakes from locking up before the fronts. This was on a 120 wagon with 1800E 4 wheel disc brakes. It would probably work with a single proportioning valve in a front rear split system.

140's used the same size rear brakes as 240's and the proportioning valves are rebuildable unlike 240 valves. They're also adjustable. Sedans and wagons used different valves so I'd try to locate a pair of wagon valves and see how it goes.

VP has the rebuild kits for ~$20. They also have new valves for ~$270 for the pair but they're for sedans.
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Old 03-17-2020, 01:01 PM   #6
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Are you plumbing it for dual diagonal brakes?

My experience using adjustable proportioning valves on a dual diagonal circuit system was an inability to limit the pressure enough to keep the rear brakes from locking up before the fronts. This was on a 120 wagon with 1800E 4 wheel disc brakes. It would probably work with a single proportioning valve in a front rear split system.

140's used the same size rear brakes as 240's and the proportioning valves are rebuildable unlike 240 valves. They're also adjustable. Sedans and wagons used different valves so I'd try to locate a pair of wagon valves and see how it goes.

VP has the rebuild kits for ~$20. They also have new valves for ~$270 for the pair but they're for sedans.
Vety helpful information.
I am running split diagonal like a 240, with 240 vented rotors and calipers in front and stock 240 rotors and calipers in the rear, but mounted on a 1800es rear axle.
I'm going to try a pair of racing proportionals for starters, all though reading this thread I'm tempted to try just running without, but my wagon is rarely loaded and rear step out us kind of why i went to rear discs as i find them less grabby than drums.
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Old 03-17-2020, 01:45 PM   #7
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Dual diagonal systems are for safety freaks.

Dual master systems with a balance bar are for performance.

Adjustable brake proportioning valves Suck Balls.
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Old 03-17-2020, 02:13 PM   #8
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Quote:
Originally Posted by Dirty Rick View Post

Adjustable brake proportioning valves Suck Balls.
Tell that to all the NASCAR teams that run them....
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Old 03-17-2020, 02:23 PM   #9
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If they run them it is because the rules prohibit dual master cylinders.
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Old 03-17-2020, 02:26 PM   #10
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Originally Posted by Dirty Rick View Post
If they run them it is because the rules prohibit dual master cylinders.
They don't prohibit dual MCs.
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Old 03-18-2020, 09:56 AM   #11
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Are you racing this car? If so, having one less thing for the driver to futz with might be a consideration to put stock valves in. If not, I used a 7 position proportioning lever in my '69 Camaro when I put discs in the rear. Again, it kept me from fiddling with it constantly, given I had only a limited number of options.

I have a friend who had an adjustable valve come apart while racing, so there's that too..
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Old 03-18-2020, 01:20 PM   #12
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To answer the OPs question, I think a set of used stock 240 limiting valves would be perfect.
You can run without them, but on a 240 you will have the rears lock-up just a tad before the front.

As far as race cars go (without diagonal circuits), the Wilwood blade style proportioning valve is one of the best.
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Old 03-19-2020, 08:52 PM   #13
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Plenty of nascar teams use dual masters, often with a blade/lever style valve as well. Some use a knob style it varies.
The best approach is to match front and rear braking with the needs. Sticking with 240 stuff you won’t be far off.
OP, a “proportioning” valve doesn’t really change the proportion of front to rear brake pressure in a linear fashion. The valve is a pressure regulator that caps the pressure. So the front and rear pressures go up the same until the rear hits the limit. After that point the rear pressure stays the same even as the input pressure (and front pressure) increases.
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Old 03-19-2020, 09:01 PM   #14
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Quote:
Originally Posted by mikep View Post
Plenty of nascar teams use dual masters, often with a blade/lever style valve as well. Some use a knob style it varies.
The best approach is to match front and rear braking with the needs. Sticking with 240 stuff you won’t be far off.
OP, a “proportioning” valve doesn’t really change the proportion of front to rear brake pressure in a linear fashion. The valve is a pressure regulator that caps the pressure. So the front and rear pressures go up the same until the rear hits the limit. After that point the rear pressure stays the same even as the input pressure (and front pressure) increases.
After the "knee" there is still a pressure rise, just at a different rate.



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Old 03-20-2020, 11:09 AM   #15
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That’s good to know. The only charts i ever saw were flat.
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Old 03-21-2020, 09:22 AM   #16
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Thanks everyone for your input, I have now got enough info to start on this. The Knee and subsequent slower rise rate chart from Wilwood is especially interesting....I’ll probably fab a quick test bed on whatever I get to see how the react. I do have a set of 1960s proportioning valves from Volvo (disc/drum ) that need rebuilding, those are adjustable under the car, but I have yet to find definitive tuning specs for them, they are just a spring and a valve so I have no idea how they would respond, or now that I have a booster would they even limit enough under full pressure.
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Old 03-21-2020, 12:00 PM   #17
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Quote:
Originally Posted by Acmontreal View Post
In my case I am running Volvo vented rotors and calipers in front and standard discs in back, but on the source vehicle the proportioning valves were toast. I can buy aftermarket manual adjust rear proportioning valves, is that what most are of you do? Or do you pay big$$ for a pair of Volvo’s rear proportioning valves? Inquiring minds want to know.
All of the above with a brake booster and 240 MC are being installed in a 120 wagon, if that helps clarify anything (probably doesn’t, all I need to know is what 240 owners are doing if not using stock proportioning valve?




Volvo 140 240 wagon Rear Brake Proportioning Valves 1973-1993

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Folks on here don't know a good deal when they see it.
how psi stock cna support?

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Old 03-21-2020, 06:10 PM   #18
Acmontreal
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Thanks for the link. I,would need to rebuild a used P valve before putting it into a brand new everything brake system. I could try rebuilding it but so far finding rebuild kits/conclusive info on calibrating the Pvalve I doubt it would work any better than aftermarket.
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Old 03-21-2020, 06:25 PM   #19
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But your question was "Or do you pay big$$ for a pair of Volvo’s rear proportioning valves?" so I linked you to cheap known good take-offs as our go to solution.

After 72 they weren't adjustable anyway.

All that said the 122 conversion guys want 68-72 145 valves not 240 as hiperfauto alluded to.

Last edited by Redwood Chair; 03-21-2020 at 06:37 PM.. Reason: After 72
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Old 03-21-2020, 10:07 PM   #20
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Cool,thanks.
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