Front brakes lock up when road is wet after replacing entire brake system

James T Duncan Sr.

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Wilmington, North Carolina
Replaced every single brake component on my TJ. Now when the road is wet the front wheels lock-up. The tires are good and the peddle is strong. Is there an adjustment for the pressure bias for front to rear pressure as the front are disks and the rear drum?
 
Replaced every single brake component on my TJ. Now when the road is wet the front wheels lock-up. The tires are good and the peddle is strong. Is there an adjustment for the pressure bias for front to rear pressure as the front are disks and the rear drum?

Did you do a stock-type replacement or a slotted and drilled get-up like what power stop promotes? I ask because I've got stock brakes (without anti-lock) and my rear wheels with dookie drums lock up fairly easily.
 
Did you install the original brake proportioning valve or was it at least a Mopar or a quality non-store brand? And are your tires aired up properly? Under inflated tires will hydroplane more easily on wet roads which helps the brakes to lock up more easily too.
 
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Replaced every single brake component on my TJ. Now when the road is wet the front wheels lock-up. The tires are good and the peddle is strong. Is there an adjustment for the pressure bias for front to rear pressure as the front are disks and the rear drum?

Are your rear brakes adjusted properly? And what Jerry asked.
 
You may need to break in the new brakes. I replaced mine a few years ago, and immediately after the fronts would lock up on wet roads. When the roads were dry, I followed Blaine's break in procedure for Black Magic Brakes (even though I put in Delco parts) and the brakes have been great.

Earlier this year I did have an issue with the brake hose rubber causing the front right brake to drag and lock, but that was not the brakes per sey...
 
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That's it. I installed the slotted/drilled rotors.

No, that’s not it. Slotted rotors are a waste on a TJ, but that alone will not cause your lock up problem. Something else is going on - a few options have been touched on above.

Slotted rotors are designed to shed gassing when the brakes get hot - such as in a track situation - to help reduce brake fade. They do not improve braking under normal circumstances, and because of the reduced surface area compared to a similar sized standard rotor, they
could actually reduce performance in normal circumstances.

The other downside as I understand it, but have never personally confirmed, is that off road the slots and holes can accumulate dirt and debris.

My money is on improperly adjusted rear drums.
 
If his rear drums are out of adjustment, they might not be engaging to their full potential, thus relying too much on the front.
The rear brakes never work at their full potential, their ability to brake is purposely reduced down to roughly 25% of their potential braking capacity by the brake proportioning valve. The purpose of that being that the rear brakes will lock up way too easily without the brake proportioning valve due to weight transfer toward the front during hard braking that unweights the rear tires. Locked up rear brakes can throw the vehicle completely out of control so their ability to brake is significantly reduced to prevent that. The front brakes provide roughly 75% of the total braking force.
 
The rear brakes never work at their full potential, their ability to brake is purposely reduced down to roughly 25% of their potential braking capacity by the brake proportioning valve. The purpose of that being that the rear brakes will lock up way too easily without the brake proportioning valve due to weight transfer toward the front during hard braking that unweights the rear tires. Locked up rear brakes can throw the vehicle completely out of control so their ability to brake is significantly reduced to prevent that. The front brakes provide roughly 75% of the total braking force.

I understand that. I'm suggesting the OPs rear brakes might be applying little to no braking, for whatever reason. (collapsed/clogged line, badly out of adjustment, corroded wheel cylinder, bad proporting valve, etc) I've had badly corroded wheel cylinders produced a front wheel locking situation because the rear was essentially doing nothing. That's why I suggested it, and why I think the OP needs to rule out simple stuff first, like making sure the rear is actually doing work.
 
You may need to break in the new brakes. I replaced mine a few years ago, and immediately after the fronts would lock up on wet roads. When the roads were dry, I followed Blaine's break in procedure for Black Magic Brakes (even though I put in Delco parts) and the brakes have been great.

Earlier this year I did have an issue with the brake hose rubber causing the front right brake to drag and lock, but that was not the brakes per sey...

That's an excellent point, and one that I think too many "brakes and oil shops" ignore instead of instructing their client how to do it. So then you get a situation where the vehicle owner does the job themselves and doesn't know about the break-in procedure at all since they've never been told to do one by a "mechanic". (On that note, always use a real mechanic shop for work you can't do yourself.)
 
How do we even know there is a problem? I can lock up my brakes… I don’t see it as an issue?

Does he have ABS?

The front brakes should 100% lock up on a non abs jeep, should they not?
 
How do we even know there is a problem? I can lock up my brakes… I don’t see it as an issue?
I wouldn't consider it to have an issue on wet streets. But I've long since learned to just be quiet and watch where it goes in hopes that enough info will get posted up to solve the problem.
Does he have ABS?
Unlikely, not zero, but unlikely.
The front brakes should 100% lock up on a non abs jeep, should they not?
They should in my world but without the before comparison of trying to lock them up on wet streets to no avail and now being able to, we're all just sorta flailing about shotgunning suggestions.
 
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How do we even know there is a problem? I can lock up my brakes… I don’t see it as an issue?

That's one of the problems/challenges of helping someone diagnose stuff like this virtually. The OP might be describing a panic stop situation, or normal braking, it hasn't been stated either way, just assumed by us as normal.
 
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I wouldn't consider it to have an issue on wet streets. But I've long since learned to just be quiet and watch where it goes in hopes that enough info will get posted up to solve the problem.

Unlikely, not zero, but unlikely.

They should in my world but without the before comparison of trying to lock them up on wet streets to no avail and now being able to, we're all just sorta flailing about shotgunning suggestions.
Sorta the same thoughts I have. I guess I’m not sure what the problem is, other then the brakes are working like they should, or so it seems without all the info
 
I replace everything in my braking system minus the master and proportioning valve. On the first drive I came to a traffic light with a red light camera. Hit the brakes and locked up the front wheels. Wow! I like it. Normal in this type of situation. Non ABS.
 
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