'00 GJC uneven break wear

Hmm... Odd pattern, the one cut line almost looks like a rock has been caught by the pad or the pad material has gone. Most pads are glued nowdays but a rivet could leave that mark. I'd take the caliper off and have a closer look at the pad face.

Either way that disc is going to have to be milled or replaced. A new pad won't seat on a surface like that. These days new hats are almost as easy to do as having the originals milled. That and depending on how deep that is you might not have enough thickness left. (do both sides at the same time)

Rear brakes are only a minor part of braking. The fronts do most of the work. When you take it apart check the piston to make sure you didn't bend it when pushing it back in. I always use the old pad and a big C clamp to press the piston back in.

They have slide pins. But usually if a caliper sticks it just wears out one pad real badly.

Take the caliper off and look (post some pics) and the folks here might be able to give you a better idea.

Only for the internal parking brake shoes.

Thanks for the reply Doug. Here is a picture of the other side:

Seems like I didn't replace the rotor when I put new pads on it a year ago. I can't remember. I know I did the fronts and put on new rotors with new pads. Maybe I should have put new rotors on the rear too...they didn't cost much. I think the fronts were $50 each.

Incidently, it's my wife's truck and she hates all the brake dust. Would ceramic pads eliminate the brake dust?

Anyway, I'll tear down one side and take some pictures and post them. Thanks for the advice.

DG

DougW wrote:

Oops, wrong side. Here is the other one:

http://i10.t> Thanks for the reply Doug. Here is a picture of the other side:

The wear pattern (clear area) should extend from the rust rim at the edge to the rim at the hub while yours only goes about half way down.

From the extent of the wear (ridges) and the deep gouges in the rotor I'm thinking that the rear pads are worn out or have already failed.

How many miles on your '00?

The only way to tell for sure is to actually pull off the wheels and examine the pads.

DC does not recommend ceramic brakes for the WJ series. I have Wagner ThermoQuiet pads and they seem to generate very little of the black brake dust

hmm.

I dunno. Were the discs like that when you put new pads on? Can't tell from the pics if there is something wrong with the setup. Generally there is only one way to put the caliper back on.

At this point I'd be looking at new pads and hats for both sides.

If there is uneven wear from inside to outside on any rotor, your slide pins are not working properly. Clean, grease, replace as required. If you live in the rust belt, just replace the pins. BTDT

Some vehicles have park> I've got a GJC Laredo 4.7 and the rear brakes are wearing unevenly. In

I'll tear into it this weekend and inspect. I will probably end up replacing the rotors and pads. I don't remember there being any issues when I put pads on last time. If there was, I would have just replaced the rotors, they don't cost much.

Thanks for the replies!

DG

RoyJ wrote:

Sounds like sticky slide pins. Stay FAR AWAY from ceramic JUNK pads. I put a set on a Lumina once.. Stopping power was GONE, lots of brake dust. Switched back to semi-metallic and problem solved.

Carl

Does the 00 use slide pins or do the pads just slide along two surfaces like they do on the ZJ?

If the surface, I've caused rear brake squawk by not thoroughly polishing that sliding surface before installing new pads. Luckily mine was reasonably harmless and I was able to cure it by pulling the pads and using a Dremel to polish the slide surfaces up, then hit them with just a teeny amount [not called out in the fsm] of silicone grease.

Yours look like the caliper itself is not applying even pressure when the brakes are applied....OR...the brakes might be dragging on the outer surface to cause that wear pattern and what is causing that may be keeping you from getting much of any rear braking at all.

Any chance you dinged the rubber seal over the piston in the caliper, or maybe that piston is wedged just a bit off kilter?

As Doug notes, best to pull them and be prepared to either have them turned or just replace the rotors after doing a really good check of the caliper and piston to make sure nothing is jammed or not reseating properly. I always use a big C clamp to retract the pistons with a helper pulling the extra brake fluid from the reservoir.

DougW proclaimed:

DougW proclaimed:

That assembly sure looks like the one on the older ZJ where the pads have tabs that just sorta slide along the edges of the caliper mounting area. However, I can't think offhand how that area being cruddy [which it is a bit from your photo] would cause BOTH sides to look so close to wearing only on the outer edge of the rotor. I would think even if the little springs that seat the shoe into the piston were not seated fully, the first time you apply the brakes they would seat.

I think in addition to rotor turning and pads, you might want to get kit for the calipers and rebuild them. SOMETIMES local brake shops might be willing to take a quick look at it and let you know if it would be better to let them do it or you can do it yourself.

Make sure the slide surfaces are not just smooth but are shiny bright and clean. A very very thin layer of silicone or lithium heavy grease might help but make darned sure you apply it with something so you dont risk getting even the tiniest amount on the rotor or the shoes.

That one groove just inside the wear pattern bothers me, almost like something is jammed where it shouldn't be.

DorkyGrin proclaimed:

I'm almost wondering if they are the correct shoe. There is also left and right pads, possibly on the wrong side? Thought they only fit one way.

That however isn't close to the rear discs on the 00. Don't have one of those in the picture archive. But on these if they give you the wrong pads, the pads may fit, but they won't be properly centered. hmm.. come to think of it, if the pad is not riding on the knuckle it could rotate or tweak the whole caliper off to one side. ...also... if there were any shims stuck in the old caliper (or broken off bits of shims) then the new pads would also sit funny. The 93 originally had separate shims on the front, but later pads incorporated them, so you don't need them anymore.

Found this site handy.

This is what the WJ rear brakes look like.

> Make sure the slide surfaces are not just smooth but are shiny bright

Thanks for the replies.

I'm pretty sure the pads are installed correctly. Not sure if there are slide pins or not. I distinctly remember cleaning pins, but I think that was on my Explorer. I put new pads and rotors on that a few months back.

I didn't get time to tear into the brakes this past weekend. I'm sure when I do, I'll just replace the rotors and pads and whatever else looks worn. Not sure how to tell if the calipers themselves are working properly. Seems like if the pistons are 'hard' to compress that there might be a problem. But how do you define "hard"?

Is there some way to tell if the pistons are sliding in and out easily?

The local auto parts store sells a kit that includes rebuilt calipers, all the hardware and pads for something like $120 each.

I'm pretty sure the pads are installed correctly. Not sure if there are slide pins or not. I distinctly remember cleaning pins, but I think that was on my Explorer.

DG

Carl wrote:

The caliper should slide freely on the pins. Basically, if you can see grease all over them, that's good enough. If you cant, make it so.

Carl

Not rilly. If they just fall back in then there is a problem which can usually be found by looking for a big puddle of brake fluid. :) That's why it takes a C clamp to push the piston back in. Your squeezing a lot of fluid through a little line.

I wouldn't go with a rebuilt caliper till you see what the pistons look like. Oh.. and never push on the brake with the caliper not on the disc and shoes in it. That will pop the piston out and make one hell of a mess.