I explained it before somewhere, but I'm pretty sure it's because of the angle that the pad contacts the rotor. Ever slid something on a surface and had it jump up and down going one way, but move smoothly if you move it the other way? Same deal with the pads, just microscopic (and very fast) jumping.

 

so your suggesting i change the pads???

 

my luck with my car=2 keyings, a lady backed into it last month and i still havent gotten the check from the insurance company, im noticing rust under the paint even though i wash it twice a week during the winter, it decided to spin out on me and kick me 6 feet into the woods on my friends road oh and the fact the parking break has to be adjusted bi monthly or i roll down my driveway back into the road if its not in gear

 

one of the reasons why i like automatics hahahah

 

real men drive stick

 

Before getting her home after buying her, a rock was kicked up into my windshield which cracked it. Plenty of door dings have occurred. She's been through two tornadoes. My "friend" drove her over a curb (since he's never paid me back, he's no longer a friend). A rock was kicked up under my hood which hit my clutch fork just the right way to break it. A gasket was left off of the firewall when service techs where looking at it. It took my two months to figure out why she was filled with water after every rain. There have been many other misfortunes.

Recently, I took her to church with me and had the resident pastor perform some blessings on her. We had had no issues since. I recommend that you guys have your cars blessed as well.