What makes a brake pad squeal in stop & go traffic?

[nthach]

I'm confused. You're original thread said you installed Advics over " turned" ROTORS. Then you had a squeak. Rear drums don't squeak. They do warp, and get dusty, and get out of adjustment. So, where is the noise coming from ? The front or back of the vehicle. ? But, meanwhile, while you have the drums off, wash down everything with brakleen, wash out the drums, take some sandpaper and take off any glaze on the drum where the shoes hit, ( don't go crazy sanding..just a light hand sanding ). Pop off the rubber grommet in the drum, line the grommet hole up to a hole in the hub where you can see the " star" adjuster. Slide the drum on. Put the lug nuts on fairly tight to center drum. Spin it. If it spins freely, it's out of adjustment. Take a flashlight and a small bent flat screwdriver and slowly turn the star.( It will only move one way). Turn the star 2 clicks. Hit the sides with a rubber mallet to set the shoes, spin again Repeat. Stop tightening star when you sense the LEAST amount of resistance of the shoes rubbing against the drum. ( You can also hear it ). Drums are supposed to self adjust when you drive in reverse and stop, but it never works. Maybe 3-4 clicks on the star is all you may need. I'm not there to see or tell. Now back to the squeaking....the front or rear ???

The squeal was from the back. Dust buildup. Took the drums off, cleaned the brakes, scuffed(and chamfered) the shoes. Lubed the contact points.

 

[50yr Street Mech]

Now we're getting somewhere Did you remove some of the glaze off the drum ? And finally, did you adjust them ? Rear drum brakes out of adjustment forces the front brakes to do most of the stopping. Also, rear drum brakes out of adjustment will give you a lower brake pedal. That's another little trick to know. If you found dust, there was "normal wear" on the shoes, which puts them out of adjustment after time. Getting off subject a bit, brake fluid needs to be replaced every 2 years. It absorbs water ( yes..even in a closed brake system. Don't ask me how, I'm not a chemist ). If you never bled a brake system, at least do this much. Get a turkey baster at the supermarket. Attach some clear plastic tubing to the end, remove the screen in the top of the master cylinder, shove the tubing in, and start suckin that junk out the best you can. Add new fluid . The master cylinder cap will tell you what fluid to use. ( Normally DOT 3 or 4 ). Eventually, it will mix with the existing old fluid, then do it again, and again, and again, until it the master cylinder stays almost " clear in color". It will save you're ABS system, you're master cylinder, you're front caliper pistons, and you're rear wheel cylinders. If you want to learn how to " gravity bleed" the entire system, let me know. It's a one man job, but takes some time. Works well. Power bleeding is the best, but I don't have the $$$$ for the set up. Just a lowly STREET MECHANIC, ( who has his own climate controlled garage now. Finally )