I installed new pads and rotors on my front axle 10 months ago. They squealed under moderate pressure at low speeds almost immediately. This seemed to come and go over the weeks. 4 months later, I decided to replace the hardware (pins, sleeves, bushings) and apply some brake quiet. This helped significantly with the squeal, but to some degree it was still there. Then a few months later, it started to vibrate (sounded like it was grinding). This happened under the same conditions and intermittently as the squeal before. Finally last week, when the grinding noise came back, it was bad enough that I had to do something about it. From the noise and vibration level, I expected to take the wheels off and find the caliper grinding into the rotor, but that wasn't the case. The pads and rotors were scored, the pads were significantly worn and there was a step at the outer (radially) edge of the pads. I took the pads and rotors into AutoZone (where they were purchased). They couldn't say what had caused the situation, but said that something was definitely faulty and replaced them all under warranty. One thing they said was to make sure that the pads didn't overhang the rotors at all (that is what had caused the step in the pads and could have caused vibration, noise, excessive heat). I took the new parts home and installed them, and sure enough the pads overhang by about 1/8".

So the caliper hardware is new,the caliper bracketis an integral part of the steering knuckle (so it can't be loose), and the caliper seems solid on the bracket. Furthermore, the rotor appears to be the right size (if it were only about 1/8" larger it would come in contact with the caliper guide pins/bolts). So I'm left with the pads must be the wrong size. However the backing plates fit perfectly on to the caliper, if they were a different size, they wouldn't fit on the caliper. It seems the only option is that I've been given the wrong model of pads, and that the correct model has the same backing plate, but a different pad or a the same pad attached in a slightly different location on the backing plate. I find it hard to believe that this has never been noticed before by other AutoZone customers.

The rotors I was given were AutoZone part # 5550, and the pads were AutoZone part# DG154 (the set I just took off) and DGC154 (the set I just got). Anybody have any thoughts....?

 

Wow the only time that happened to me was on my Volvo. BUT the Rotors did lose Diameter after driving 200000 miles with salty roads during the winter. just like you, the Pads started to creep arount the Outer Diameter of the Rotor. When it his that rusty edge it feel shorrible. I got new rotors. But you say you replaced both the Rotors and Pads.
Teh new Pads are still too large? I was thinking maybe it was a bad Lot from the factory. How are teh Pads touching on the low end? I mean are they way down by the Hub where they should be or is the whole pad shifted up?

 

Yeah the pads and the rotors were new 10 months ago, and I just got brand new pads and rotors two days ago and they are the same on both sides. It appears like the entire pad is shifted radially outward, it overhangs the rotor by about 1/8" and there is about 1/2" gap or more between the radially innermost edge of the pads and the hub of the rotor. It really does look like it is the wrong pad, but I just can't my arms around the idea that AutoZone has been handing out the wrong pads to Blazer owners nationwide and no one has noticed. The pads I have been given both times are what are indicated on their webpage as being correct for my vehicle. I suspected there might be different part# for the towing package version of the blazer, which I have.However, I called a dealer parts counter and they said that isn't the case.

 

OK, so there is a large gap on the Inner edge.
I bet the wrong pads are in the wrong box and that one AutoZone got a shipment of bad ones.
Did you try another Autozone,;carry in the 'bad' pads and ask for the same part number? Size them up and see if they are different.

 

Well I know that the old pads (the ones I just took off) and the new ones are the same size (we compared the parts side by side at the store), so that means it would have had to happen on both the semi-metallics that I bought 10 months ago and the ceramics I got two days ago (though they were both duralast brand). But it would be a brilliantly aggravating coincidence that explained everything! Thanks for the input, I'll check it out.

 

They definitely sound like the wrong pads if they overhang like that, I have never had good luck with autozone giving me the right part, I have gave up on them.

 

Yeah, I love my local autozone because the employees are incredibly friendly/experienced/helpful. They stand behind their warranties, and when you do get the correct part, they are good quality for dirt cheap. I will say that I don't think I'll ever buy tools there again. The first time I changed my disc brakes, I bought a standard set ofallen drivers for my socket wrench to remove the caliper guide pins/bolts, went home andnone of them fit (including the 3/8", which is what the guy at autozone said it probably was). So, I went back and purchased the metric set, at that point not too upset. But I got home and none of the metricbits fit either.So I went in search of a strangestandard set with1/32" interval allendrivers. Wasted an entire day before I came up with an idea that I at first found so absurd I laughed it off: the 3/8" driver Ithat came in the set from AutoZone was, in fact,not 3/8". So I went to Advance Auto to buy a 3/8" driver, and then went back to AutoZone to have a conversation with the manager...

 

Wrong pads or wrong rotors? What is the gap between the caliper mounting bracket and the rotor? I believe your rotor diameter should be 10.82" or there abouts...

Do you still have the old parts you removed the first time around to compare to?

 

The rotor diameter is 10.5". The new one is the same as the one I just took off, and the part number cast into the rotor matches what is indicated on their webpage. Also, I checked NAPA's webpage, and it indicated that their rotor for my truck is 10.5" in diameter. Furthermore, the gap between the rotor outer diameter and the caliper guide pin/bolt is only about 1/8". For those reasons, its my belief that the rotor is correct. I think the rotors changed to 10.82" for the 98's (according to my research on NAPA).

 

Ok, just trying to provide another view point.