Strange front brake rotor wear question

I decided to try out the black magic pads, new centric premium rotors and calipers on my 2000 XJ. While pulling the front brakes apart I noticed the inside of the rotors didnt look like they had been getting pad pressure. They were all rusty and pitted but the outside of the rotors looked normal. Does anyone have a clue as to what would cause this? It would explain the lack of breaking power I have but I am wondering if I may have a master cylinder or prop valve issue. I want to make sure I get that addressed before I slap all new parts on.

Check for indents on the slides, I suspect the inside pad is locked up.

Could be the caliper pins/bolts are rusted and seized...

Could be you have the wrong rotors? I don't know about your 2000. but I once received the wrong rotors for my 96. I now take an old rotor with to the parts store and a tape measure, flop the new and the old side by side on the counter, eyeball, then measure.

The caliper has to slide on the pin/rods/bolts. It may be stiff but it has to move on the rods. It is possible to have a bushing or a sleeve catch or fold and get jammed onto the pin/rod. I always clean out the rod opening on my caliper and apply a dab of high temp silicon lube on the rod. Look in the pin/rod hole on the caliper with a flashlight to see of something ins folded or it is full of crap.

The pads can wear a notch into the caliper guide, pretty common. You can either weld and dress the notch flat or Bendix makes a tiny tab that is rounded and fits onto the pads so they won't catch. It is actually a kit so you can put the tab on there and adjust clearance also. Finding the kit might be difficult.

8Mud has given some good advice.

On many vehicles there is a separate caliper bracket that takes stainless brake pad shims. The pads move smoothly if there is no rust between the shims & the caliper bracket. On our XJ's its all integrated into the axle knuckles. Where the pads ride can develop a "notch" so one or both of the pads fails to move smoothly and hang. Filling with weld & grinding smooth is a common repair. If you don't have access to a welder, then replacing the knuckles with used without this problem is another solution. Also make sure the slide pins move smoothly. They may require a bit of lube, but if they are worn or damaged then replacement of warn parts is also needed.

One thing I forgot, either cross threaded bolts and/or bent pins can also cause issues.

I will check all this. Thanks

uneven pad wear is 99% of the time cause by improper movement of the caliper, 1% of the time by incorrect centering of the rotor. As the guys above pointed out check to make sure you have the correct hardware with the pads, ie if they came with the SS channel sleeves that the pads rest on, and please for the love of god make sure you lube the pin sleeves. I always lube the channel regardless if it has a SS insert just to ease movement, but I know a lot of guys don't if it has a new channel sleeve. The pin sleeves should slide easily back and forth by hand inside the rubber boots prior to reinstalling(#1 cause of uneven pad wear). This should be done every brake job at a minimum and depending on your climate or level of offroading probably once a year.

To check the rotor centering(rare) take a set of dial calipers and measure the gap between the inside of the pads(new ones so they are even) and the surface of the rotor on each side via the top 'window' on the caliper. they should be within .001-.003 of each other. If for some reason it is off you can use thin washers from the hardware store to correct. Unless someone changed out the calipers for remans or tweaked the bracket this would be very rare. Most of the ones I've run across were from reman calipers that had the ears sanded for cleaning or were a 'multiple vehicle' application.

8Mud said:

Bendix makes a tiny tab that is rounded and fits onto the pads so they won't catch. It is actually a kit so you can put the tab on there and adjust clearance also. Finding the kit might be difficult.

Click to expand...

OK you have my attention, where might one find these????

What is it called?

Part number?

I'm no welder (yet) and I need these on one side of my 87 Wagoneer. Not looking forward to welding/grinding as an experimenting beginner welder and I don't trust anyone I know, ....or changing out the expensive knuckle and ball joints just to solve the notch problem.:smsoap:

I used a hand file and got some relief for now, but the pads have too much play on the slides and catch and break the spring clip some times.

I'll go digging through my junk when it warms up and see what I can find. I tired searching on the internet when this thread first came up and had no luck.

I've got two kits someplace, only seen them once at my local auto parts store and that was a long time ago.

I welded and filed mine.

I'll try searching some other terms and see what I can find.

Well thanks for all the replies. After installation of the new centric premium rotors and calipers and the black magic pads I can report that my Cherokee now stops incredibly well.
I have a 6' x 10' utility trailer that I haul around and will be putting magnetic brakes on it's axle as well.

Tampa XJ has the right idea. If the inside of the rotor is not wearing, then quite simply it is not getting any pressure from the inside pad. And what provides the pressure to the pads....the Caliper. And the caliper piston is on the inside, no coincidence. When your caliper piston bore gets all crudded up with dirt, brake dust, rust, etc, it doesnt move freely. If it doesnt move freely, you get no pressure transfer. Rebuild your calipers and the problem most likely will go away. At the same time, check the slides or pins, but they are usually ok. To damage that stuff, you really had to have had a bad event occur, which you would already know about.