Options for proportioning valve on 4 disk conversions

[turbobitt]

Looking for some sugestions here. Going to Aerospace brakes on all four corners and assuming the factory proportioning valve would not be the best choice.

I see brass and aluminum Disk/Disk proportioning valves as well as a fancy Willwood adjustable that appears to have the same bolt pattern as a stock valve. What is really needed.

My car has bigger tires in the rear with front skinnies so I'm assuming I won't need to turn down the rear braking nearly as much as a car with larger front tires.

Opinions ?

 

[happy4444]

Bumppppppp. debating the same thing

 

[Turbo6inKY]

Disc brakes need a lot more pressure to work properly than the drums. Drums have a lot more contact area between the friction material and the drum, and the drum rotation against the shoes also creates a moment in the shoe that helps press it against the drum mechanically, so line pressure requirements are lower. The smaller contact area with discs means you need more pressure at the contact point to achieve the same amount of friction. The stock prop valve also has a residual pressure function to counteract the springs inside the drum and keep the shoes up against the drum. That residual pressure is too much for a disc set up and you'll end up dragging the rear brakes.

Basically, if you switch to rear discs without replacing the stock prop valve, you'll get excessive pad wear and heat buildup because it'll drag the rear brakes constantly, but then it won't stop as well because the prop valve will limit pressure to the rears when you actually use the brakes.

For four wheel disc, you need an adjustable prop valve and a 2psi residual pressure valve on the rear circuit. The 2psi is enough to prevent most pad knockback, but it won't drag the brakes like the stock valve, which is likely closer to 10psi residual pressure.

A non adjustable disc brake prop valve from a car that had four wheel discs would work, but you'd have no way of knowing if the brake bias was optimal. The only way to get it right for your car, brake system, and tire combination is to use an adjustable prop valve.

 

[TURBOELKY]

http://www.highwaystars.net/brake-p...places-gm-1257189-4-wheel-disc-brake-systems/

 

[happy4444]

http://www.highwaystars.net/brake-p...places-gm-1257189-4-wheel-disc-brake-systems/

Its this versus an adjustable wilwood.

The wilwood requires removal of the existing prop valve, so essentially new front lines that dont interconnect, not to mention the rear line.
The new brass block (above), which everyone sells is basically plug n play with the stock lines but it self proportions front and rear... but the question is how good is it?

 

[Turbo6inKY]

Its this versus an adjustable wilwood.

The wilwood requires removal of the existing prop valve, so essentially new front lines that dont interconnect, not to mention the rear line.
The new brass block (above), which everyone sells is basically plug n play with the stock lines but it self proportions front and rear... but the question is how good is it?

I think the answer is going to be "good enough for a street car."

So it really depends on what he's doing with it. If he doesn't need to precisely dial in the bias for maximum braking performance, that block is the easy button.

 

[turbobitt]

Its this versus an adjustable wilwood.

The wilwood requires removal of the existing prop valve, so essentially new front lines that dont interconnect, not to mention the rear line.
The new brass block (above), which everyone sells is basically plug n play with the stock lines but it self proportions front and rear... but the question is how good is it?

I had this valve in my car (with no additional 2 lb residual valve)and it worked ok but could have used a little more braking in the rear with the big tires in back and small tires in front. I just took it off because I switched to a dual caliper rear and felt the need to follow the brake instructions precisely and use the adjustable proportioning valve and 2 lb residual valve.
AG.

 

[happy4444]

I had this valve in my car (with no additional 2 lb residual valve)and it worked ok but could have used a little more braking in the rear with the big tires in back and small tires in front. I just took it off because I switched to a dual caliper rear and felt the need to follow the brake instructions precisely and use the adjustable proportioning valve and 2 lb residual valve.
AG.

What adj prop valve you going with?

 

[forcefed3.8's]

I assume you have a manual master cylinder. I have a wilwood adjustable that I have set to send full pressure to the rear. I started out taking pressure out for the street, but just leave it now, and havent had any issues with the rears locking up on the street. I have 12.19" wilwood fronts and 11" dual caliper aerospace in the rear. I run a 1 1/8" master with both outlets tied together then split off so all calipers get the same volume. The breaks are firm, but responsive, it doesnt take much pedal travel to have breaks. To me the pedal feels like my 2011 2500 silverado.

 

[Ken Adams]

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[turbobitt]

What adj prop valve you going with?

The adjustable is a Right Stuff PV01 but they are all similar in design.
AG.

 

[HotAirGN]

I am trying to run new brake lines and need to know what I need. I have a wilwood rear disc setup and front ssbc dual calipers. I bought a wilwood proportioning valve. Figured out today that I need to replace my original iron disc/drum proportioning valve. Do I buy the highway stars disc/disc and not use the wilwood knob I have or do I still use both? Want to place an order ASAP.

 

[happy4444]

I am trying to run new brake lines and need to know what I need. I have a wilwood rear disc setup and front ssbc dual calipers. I bought a wilwood proportioning valve. Figured out today that I need to replace my original iron disc/drum proportioning valve. Do I buy the highway stars disc/disc and not use the wilwood knob I have or do I still use both? Want to place an order ASAP.

I found out like you and didn't even know about it. I have same setup pretty much with wilwood front and rear conversion. I went with the wilwood master cylinder and added their proportioning valve right under it.

The brass block mounted to the frame screws everything up but you have two options...

1. You remove the brass block on your frame rail and add in the blue wilwood pressure valve (check summit racing). This requires custom front and rear lines you have to make yourself but if you made it this far it shouldn't be anything you can't do. This allows complete proportioning of your brakes by the valve you added.

2. You remove the prop valve you installed and replace your stock brass block with one that's meant for disk brakes all around. It's supposed to be preset with proportioning and I don't think you can adjust it. I never heard any negative about it but like I said I'm not sure if you can adjust it further.

I went with option 1 and wasn't in a hurry to have it working since I was already up to my neck.
I think option 2 will work as well and I may have gone that route if I were to do it again. Let me know if you have any questions