Adjustable proportioning valve for ABS Delete

[LoCascio_Inc]

So I’ve deleted my ABS system and I’m trying to dial in my new proportioning valve.

My new brake system consists of the original vacuum booster and master cylinder with 3/16 braided stainless lines to a Wilwood adjustable p-valve.

Front brakes are braided stainless 3/16 lines from the p-valve to the factory 3/16 hard lines on the frame. Calipers and everything at the wheel is factory.

The rear brakes are a braided stainless 3/16 line to a 10lb residual valve to the factory 1/4 hard line on the frame. Everything from the rear hard line back is factory.

The brake pedal feels firm and great and the brakes work great in normal operation but the rears lock up a little still if I completely stand on the brake pedal, even with the p-valve turned all the way out (less rear brake). Nothing dramatic, but it seems odd.

Is this a sign that the front brakes aren’t getting enough pressure, or that the rears are somehow still getting too much or normal for a truck without ABS.

All in all, it’s waaaaay better than the twitchy ABS locking up the rears constantly.

 

[Mr_white_obs]

Did a very similar thing to my '97 for the exact same reason. Very useful mod and totally changed the feel of the truck!
But seems odd. You double checked that the front brakes were bled properly, not drawing any air into the system through a tiny pinhole I'm assuming. Also, you checked your front pads/rotors/calipers for leaks and wear? Just knocking the obvious stuff out of the way. The only other thing I can think of is the residual valve, but I can't see that making any sort of difference with hard brake applications.

Are you running a NBS master cylinder by chance, or is that original too?

 

[LoCascio_Inc]

Did a very similar thing to my '97 for the exact same reason. Very useful mod and totally changed the feel of the truck!
But seems odd. You double checked that the front brakes were bled properly, not drawing any air into the system through a tiny pinhole I'm assuming. Also, you checked your front pads/rotors/calipers for leaks and wear? Just knocking the obvious stuff out of the way. The only other thing I can think of is the residual valve, but I can't see that making any sort of difference with hard brake applications.

Are you running a NBS master cylinder by chance, or is that original too?

Regular Gmt400 master. I don’t detect and leaks and I’m pretty sure everything was bled properly. The pedal is nice and firm.

 

[mr_josh]

I don’t know... I have never driven a non-ABS truck that wouldn’t lock up the rears when the bed was empty and the pedal stomped.

I think if you can drive it easily in average conditions and modulate pedal pressure to maintain control of the rear in a panic stop, that’s probably what you can expect from a non-ABS pickup truck.

 

[Gibson]

So I’ve deleted my ABS system and I’m trying to dial in my new proportioning valve.

When you got rid of the ABS, you eliminated any "proportioning"
of pressure.
The ABS modules have/had a "Combination Valve" mounted on them.
Depending upon the brake system; JB5/JB6/JB7/JB, the combination valve had a pressure value built into it that had a factory pressure rating matched to the model of rear brakes
I've used the Wilwood valves, they DO NOT "proportion" anything.
They are an adjustable "Flow Rate" valve, and they were designed for lighter weight vehicles that don't have much of a change in weight.
Not like a truck that might be empty,, or have a 1,000 lbs. or more in the back.
Of course you can lock-up the rears,, your brakes are now back in the old days of tech.
Your gonna have fun on a slippery surface,,, and if your in a bad accident you might have to explain to your insurence company,, or a judge about how you eliminated the factory safety system in the brakes.

 

[LoCascio_Inc]

When you got rid of the ABS, you eliminated any "proportioning"
of pressure.
The ABS modules have/had a "Combination Valve" mounted on them.
Depending upon the brake system; JB5/JB6/JB7/JB, the combination valve had a pressure value built into it that had a factory pressure rating matched to the model of rear brakes
I've used the Wilwood valves, they DO NOT "proportion" anything.
They are an adjustable "Flow Rate" valve, and they were designed for lighter weight vehicles that don't have much of a change in weight.
Not like a truck that might be empty,, or have a 1,000 lbs. or more in the back.
Of course you can lock-up the rears,, your brakes are now back in the old days of tech.
Your gonna have fun on a slippery surface,,, and if your in a bad accident you might have to explain to your insurence company,, or a judge about how you eliminated the factory safety system in the brakes.

Thank you for the advice but I’ve already tested it multiple times it light and heavy rain and this current set up is far better and more stable in every condition than the janky ABS that was on it before. I own multiple early 2000’s sports cars and I know how a good, OEM ABS system from the same general time period should perform. What I removed from this 1998 truck, malfunctioning or otherwise, was not safer.

 

[Andrew Warfield]

When you got rid of the ABS, you eliminated any "proportioning"
of pressure.
The ABS modules have/had a "Combination Valve" mounted on them.
Depending upon the brake system; JB5/JB6/JB7/JB, the combination valve had a pressure value built into it that had a factory pressure rating matched to the model of rear brakes
I've used the Wilwood valves, they DO NOT "proportion" anything.
They are an adjustable "Flow Rate" valve, and they were designed for lighter weight vehicles that don't have much of a change in weight.
Not like a truck that might be empty,, or have a 1,000 lbs. or more in the back.
Of course you can lock-up the rears,, your brakes are now back in the old days of tech.
Your gonna have fun on a slippery surface,,, and if your in a bad accident you might have to explain to your insurence company,, or a judge about how you eliminated the factory safety system in the brakes.

Alright, alright, alright. It's another "OBS Lawyer" you're no Matthew. Lol

 

[Chillin Dylan]

OP, would you mind posting a couple pictures of your brake setup and what part number valve you used? I’m in the middle of doing an ABS delete on my 95 2500 and am just curious how you did yours. I value function over form on things like this, but I don’t want it looking like the factory yarn ball of ABS crap either.


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[thegawd]

yarn ball hahaha! that's funny. the purpose of all the loops before the fittings is to act like a cooler. it is absolutely engineered on purpose. I would keep them even if you delete the abs. I cycle my abs any chance I get to keep it working correctly and to verify it's still working. I believe this exercise keeps it functioning.

do as you will, I'm no lawyer. ;-)

Al

 

[LoCascio_Inc]

The loops are engineered for a reason but it’s not for cooling. It is to accommodate the body of the truck flexing independently from the chassis.

I went with braided lines after failing to properly flair stainless hard lines...

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