What does this brake pad wear indicate?

[colleen]

If inclined, read my ‘oops I did it again’ post for history. Just looking for a seasoned pro to maybe clue me in on the mechanics of why my brake pads look like this! This is just one pad on the outside edge, but both ends of the outside pad look like that, and only the bottom of the inside pad. About 15 degrees angled wear.

The most material is taken off the outside top, followed by outside bottom, followed by inside bottom (least), with inside top just abrasion. Not a huge difference in material taken off but a noticeable difference. The ‘angled wear’ I’m referring to is the grey area at the end of the pad. The orange is antiseize.

here’s a pic of both. about 1/16th inch more material on the outside pad.

DRIVABILITY ON THE CAR: It seems like when I drive and use my brakes, that there is a certain point on the rotor or components that is like a bump, and it clicks when I brake, faster if going faster. So imagining the 360 degrees my axle is spinning, it makes perfect sense that the pads would be wearing like this, they are encountering a definite obstacle. (I think) But I can’t see it at all on the rotor. That is what it FEELS like. I can feel the impediment (feel the click) in the brake pedal. Mild groaning around corners from that wheel. This was not a slow onset problem, like the bearing going, going, gone. This rotor/brake was completely fine one day and screwed the next. I believe it to have been caused by not having the tire on correctly (snugged up to the rotor), and lugs only hand tightened when I lowered it. I saw the tire go to an angle when this happened.

Visually looking for any inconsistencies in the hub/rotor itself is negligible except for a tiny bit on one portion of the hub, and it’s so slight that I’m not sure.

And, I did what I WASN’T SUPPOSED TO DO – I put caliper lube on the pins last time I undid the caliper (last week, after this happened). That’s not the CAUSE of the problem, though. I just don’t think I helped. Couldn’t find silicone paste. spray, yes. paste, no.

I was able to compress the piston itself with a humongous pair of pliers…pinched off the brake line and when piston compressed, brake fluid drained into my home-made catcher bottle. Trying to visualize how the caliper could cause this is somewhat difficult.

Also did a side to side and top to bottom shake on the tire while the car was up – looking for failed tie rods or ball joints – didn’t get looseness. I sat there spinning the rotor for awhile, and heard a very slight friction noise coming from the back of it where the axle goes into the tire, around the bearing vicinity. This was only noticeable because it would happen on one particular portion of the 360 degree rotation.

THANKS IN ADVANCE FOR REPLIES!! 🙂 trying to keep my spirits up even though I have a long trip to take soon and so far have NO IDEA what is happening with my car. sucky. As a final note, the way the car is driving right now, is a major safety issue, that’s why I’m concerned. It’s not just like a noise you hear and don’t worry about. I downshift into first gear now just to avoid using my brakes at all, in fact I’m biking everywhere I need to go for now unless necessary to drive. Haven’t taken the car on the freeway.

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Topic

[Justin]

It indicates the calipers are sticking a bit… Not an end of the world safety situation, but it is something you should look into.

Disassemble the caliper bracket, and remove all the slide pins… presumably, you already did this or you wouldn’t be showing us your brake pads. Clean everything with plenty of brake cleaning solvent – heck, I often bring everything to the kitchen sink and wash it in dish soap/degreaser… then dry it.

Regardless, replace the pads with OEM (or OEM-Like material – don’t go cheap here. If OEM is synthetic, don’t even think about going with semi-metallic unless you like brake noise), and turn (or replace) the rotors unless they are smooth and true (if you have any pulsation in the pedal or steering wheel when applying the brakes, you need to address the rotors).

Finally, re-assemble with a LOT of high-temp silicone grease. Personally, I like the AGS/Sil-Glyde for slide-pins, and I load it up until it cannot take anymore. Always replace the plastic/rubber caps to keep water/road-grime out of the slide pin area. I think Eric uses a similar 3M product, but regardless you MUST use a hi-temp silicone based product. Do NOT use any petroleum/molly grease (i.e. do NOT use wheel-bearing grease).

Where the pads touch the caliper bracket (i.e. the pad ears), I put a little brake grease, too. For this, I prefer the Permetex Ultra (Purple stuff.) It is a lot thicker, but tolerates a LOT more heat than the AGS/Sil-Glyde, but a lot of forum posts indicate this stuff washes off easier, too. Either way, if you use any grease on the pads themselves, you need to use the highest temp grease you can get.

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Finally, you need to do a break in process.

1. Pump up your pedal until everything is nice and seated.
2. Start the vehicle
3. Pump it some more (now you have power assist).
4. Slowly back up (or pull forward) and verify you have working brakes.

5. Slow the vehicle down from 10 to 15 to about 5 mph about five (5) times… (AVOID Stopping)

6. Same thing as above but from about 20 to 25 to 10 mph about five times… (AVOID Stopping)

7. Same again but from 30 to 40 to around 15 mph about five (5) times… (AVOID Stopping)

8. Same again but from 45 to 55 mph to around 20 to 25 mph about five (5) times (AVOID stopping)

9. Same thing but from 60 to 70 mph to about 30 mph about five (5) times (AVOID stopping)

10. Repeat #9

The key is you do NOT want to stop with hot pads on the rotors because it makes a spot that once cooled you may feel as a pulsation. If you need to stop, slow-down to about 5 to 10 MPH then use the parking brake to come to a complete stop, but do NOT have the brake pedal down (except just enough to light your brake lights). If you do this procedure (or similar), you should have a nice, shiny brake rotor that looks like a mirror, has brake pad friction material embedded on it, and your pads should match up perfectly WITHOUT being glazed. You will have perfect, smooth feeling brakes that are truly awesome and last at least 30,000 miles (probably more like 60,000). banana:

[Author]

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