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Old 01-11-2011, 07:39 PM
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combination valve

if using a combination valve , is a proportioning valve still needed on a front disc , rear drum system?
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Old 01-11-2011, 07:56 PM
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If you are talking about a valve that has a pressure adjuster with a built in residual valve then thats all you need.
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Old 01-11-2011, 08:02 PM
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Quote:
Originally Posted by atcoed
if using a combination valve , is a proportioning valve still needed on a front disc , rear drum system?
You do not have to add a prop valve unless the brake bias isn't what is needed for your vehicle. So if the brake performance is good as-is, you're golden.

The OEM combo valve contains a proportioning valve. If it's not biased correctly for your application, the combo valve's proportioning function can be disabled and an adjustable prop valve installed instead.
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Old 01-11-2011, 08:46 PM
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I have large surface area piston front discs; rear drums.
I was planning to install adjustable proportioning valve but my brakes work so well I put that project on the back burner.

One way to verify the proportioning function of a combo valve is by comparing pressure reading of front and rear brakes.

Can test brake balance by practicing emergency stops through turns on your wet test track to verify back brakes don't lock up early and send you in a tail spin.
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Old 01-12-2011, 08:27 AM
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cobalt327, i have 11" metric dics on the front, 9" ford drums on the rear with 31" tall tires. my master cyl is the one from heidts for disc/ drum (manual) that has the combination valve .

im not getting the braking i think i should get.
how can the proportioning function be disabled ? And then is the adj. prop.valve installed in the rear line?
i think the taller tires are causing this problem, what you think ?

Thanks for your comments and help.

Roger
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Old 01-12-2011, 08:51 AM
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Quote:
Originally Posted by THERACER
cobalt327, i have 11" metric dics on the front, 9" ford drums on the rear with 31" tall tires. my master cyl is the one from heidts for disc/ drum (manual) that has the combination valve .

im not getting the braking i think i should get.
how can the proportioning function be disabled ? And then is the adj. prop.valve installed in the rear line?
i think the taller tires are causing this problem, what you think ?

Thanks for your comments and help.

Roger
OEM combo valves have a fitting that is removed and a small rubber valve (called a piston in the image) is removed before reassembling the combo valve (see image below), but I'm not sure exactly what you have.



Larger diameter tires and wheels is one reason the rear braking may be lacking. Both their height and weight can work against you.

The adjustable prop valve is plumbed into the rear brake line. Most times, one line leaves the master, then splits into two lines, usually at the axle housing. The adjustable prop valve goes into the single line to the rear before it splits.

The suggestion from 001mustang to check your front and rear line pressures is a good one- you should consider making up a gauge (or you can buy a ready made gauge kit) to do just that.
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Old 01-12-2011, 10:42 AM
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Thanks Cobalt, thats what i have . I' ll give it a try.
I have also been investigating: I think the CPP-MCPV-1 master cyl . will do the same thing, at least that is how I understand how it works.
Anyone have one of these?

Thanks, Roger
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Old 01-12-2011, 10:30 PM
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Quote:
Originally Posted by THERACER
cobalt327, i have 11" metric dics on the front, 9" ford drums on the rear with 31" tall tires. my master cyl is the one from heidts for disc/ drum (manual) that has the combination valve .

im not getting the braking i think i should get.
how can the proportioning function be disabled ? And then is the adj. prop.valve installed in the rear line?
i think the taller tires are causing this problem, what you think ?

Thanks for your comments and help.

Roger
You say you are not getting the braking you think you should have right? What is it doing? Hard pedal? Low pedal? Good fronts but no rear brakes? The opposite? Need more details to find a solution.

If you can't tell if you are locking up front or rear brakes, or which are locking up first, try locking the brakes in a gravel parking lot. Even at low speeds you will be able to see what is going on without putting yourself in jeopardy.

Let us know what is going on and we can help from there.

Andy
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Old 01-13-2011, 05:38 AM
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AOSBORN, I'll have to do the test to see which is locking first ,(IF EITHER).
i have a normal pedal, it just seem like the brakes are not applied to the max.
I have 31x18.5-15 rear tires and 9" ford 11" shoes in rear.
The master cyl. has the non adjustable combination valve, which I thought should have maybe one that I could adjust, like the one from CPP (MCPV-1)
These are manual brakes.

Thankd for your response, Roger
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