Rear disc conversion working too well
Thread Starter
Senior Member
Joined: Nov 2010
Posts: 976
Likes: 5
From: Cloquet, MN
Year: 2000 Ltd.
Model: Cherokee
Engine: 4.0L I6
The prop valve does nothing until you rapidly apply (slam on) the brakes. You have to have enough fluid flow to expand the seal on the plunger. I don't know where you are getting your proportions but you want equal pressure under normal breaking (50/50 if you will) and then reduce the rear pressure rise under hard braking only, which would apply to disc and drum rear brakes alike. This issue is under light braking only.
CF Veteran
Joined: Jul 2011
Posts: 2,164
Likes: 1
From: Warren, Pa
Year: 97
Model: Cherokee
Engine: 4.0L
I'll try to answer the questions as best I can...
Front brakes are stock. I believe I changed the pad and turned the rotors soon after buying the Jeep a couple years ago. Still in great shape. The left caliper was replaced as well as the brake hose because it was sticking. Right one has not been changed. There is no pulling right or left when applying the brakes to indicate a sticking caliper in the front and I have a hard time thinking both the original and replacement would stick the same amount. Hubs do not heat up either. When I've had calipers stick in the past it's not a problem with them not engaging, it's a problem with them not releasing and dragging. BNJeepsta, how much were your calipers sticking, was it enough to heat up the hubs? I suppose it wouldn't hurt to check them and verify they are smoothly operating.
The guts of the proportioning valve were changed in their entirety (plunger, spring, cap) when I did the swap. ABS is all there and functional.
When I changed the brake hose on the front left side I also purchased one for the right but have yet to install it. I may try doing that when I get some time since I have it. It is not collapsed, but that does not mean it's not expanding a little which could plausibly create this symptom.
Master cylinder is OEM, I've had no need to get into it.
What defines a "grippier" pad? I usually just get the economy ceramic pads if memory serves me right.
Front brakes are stock. I believe I changed the pad and turned the rotors soon after buying the Jeep a couple years ago. Still in great shape. The left caliper was replaced as well as the brake hose because it was sticking. Right one has not been changed. There is no pulling right or left when applying the brakes to indicate a sticking caliper in the front and I have a hard time thinking both the original and replacement would stick the same amount. Hubs do not heat up either. When I've had calipers stick in the past it's not a problem with them not engaging, it's a problem with them not releasing and dragging. BNJeepsta, how much were your calipers sticking, was it enough to heat up the hubs? I suppose it wouldn't hurt to check them and verify they are smoothly operating.
The guts of the proportioning valve were changed in their entirety (plunger, spring, cap) when I did the swap. ABS is all there and functional.
When I changed the brake hose on the front left side I also purchased one for the right but have yet to install it. I may try doing that when I get some time since I have it. It is not collapsed, but that does not mean it's not expanding a little which could plausibly create this symptom.
Master cylinder is OEM, I've had no need to get into it.
What defines a "grippier" pad? I usually just get the economy ceramic pads if memory serves me right.
Thread Starter
Senior Member
Joined: Nov 2010
Posts: 976
Likes: 5
From: Cloquet, MN
Year: 2000 Ltd.
Model: Cherokee
Engine: 4.0L I6
Junior Member
Joined: Oct 2012
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From: Toledo, Ohio
Year: 1999
Model: Cherokee
Engine: 4.0L
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Joined: Feb 2015
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From: Edmonton, AB.
Year: 2000
Model: Cherokee
Engine: 4.0
If you install rear discs in a disc drum system, it only makes sense to me that you should change the master cylinder too. Drum brakes employ a residual valve (in the master cyl) to keep a little pressure in the wheel cylinder to keep the cups expanded (sealed), springs return the shoes to prevent drag.
Calipers (discs) rely on seal distortion to pull the caliper piston back and prevent drag. They Do Not use a residual valve as it's not needed.
Basically your rear pads are already in contact with the rear rotors before the front get a chance to react.
Light brake application is all thats needed to causes the situation you've got. Harder application overcomes (covers up) the situation.
I'm not the Guru of these things but it only makes sense.
Calipers (discs) rely on seal distortion to pull the caliper piston back and prevent drag. They Do Not use a residual valve as it's not needed.
Basically your rear pads are already in contact with the rear rotors before the front get a chance to react.
Light brake application is all thats needed to causes the situation you've got. Harder application overcomes (covers up) the situation.
I'm not the Guru of these things but it only makes sense.
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