When breaking at speeds 25 and above, the brakes squeak. I was curious what exactly is going on that makes them squeak. Pepboys said they were good, but as some of you know they ****ed up already so I cant be sure.
2001 Grand Cherokee Limited-4.7 V8-Quadra Trac II-Flowmaster Super 44 with 3" exhaust
Several factors will cause brakes to squeak. The primary cause is friction material getting deposited on the rotor due to cheap pads with incorrect carbon or Kevlar content. The other major issue is pads that are not isolated with shims. My Background is BMW parts and service and brake squeak is a universal issue that can be cured without spending a lot of money. Use Quality part, no cheapo rotors or pads, look for OEM brands to ensure proper steel and pad compounds. Use brake shims with no brake pad paste.
The pads could be old and on their way out but I think even Pep Boys would catch that. My guess is that there is a spot that is glazed over on the pads. Mine have been squealing a bit recently and I'm attributing it to that. But if you are worried go see some other shop.
Eric - '02 Laredo Grand Cherokee Build Thread
Same thing that makes a glass squeal when you dunk your finger in water and run it around the rim - friction "make and break" - or, more simply, "slip and stick."
Check your rotors for glazing. If present, take them to a shop and have them turn about a thousandth off of the surface to remove it. While they're doing that, put a sheet of 120-grit on a block of wood or metal (to back it up and make it flat) and sand the surfaces of your pads to remove any glazing building up there. You don't need to remove a lot - just change the surface texture.
I just ran into this sort of thing with one of my wife's co-workers - it was caused by her being too gentle with her brakes - they'd heat up from use, but wouldn't wear down at all. I gave her the same advice - took me about five minutes of driving and talking to her to sort out the problem.
Fortunately, we caught it early - she may have been able to solve the problem entirely through a slight shift in driving habit (don't stomp on the brakes unless you have to, but be a bit more positive when you do step on the pedal.)
Glaze is a common factor for squeaking, but I'm suprised no one mentioned hardware. If the clips (holds the pad to the caliper) are old and worn out then they basically cause the pads to be loose and vibrate or rattle around. The metal clips rattling against either caliper or pad will cause a very high pitched fast squeal when braking. I'd highly recommend looking into that whenever you plan on changing your pads if the de glazing and cleaning of the rotors doesn't help. A hardware kit costs about $5. I'd also recommend putting brake lubricant (Autozone sells little packets so you don't have to buy a jar) on all contact points of the clips, caliper pins, and piston to prevent sticking.