My 300ex's rear brakes a really sqeaky but on when you put the brakes on.It stops good but is kind of annoying.The brake pads just got replaced and I checked the width with a micrometer.The brake pads only have about 4 rides on them.

They are preimeir brake pads.

 

my buddies with 300ex and mine all squeek too.ours are the front brakes though,i just got DP rear brakes,they are not on yet but i will let you know if they squeek or not

 

I'm runnin SBS pads on both front and rear and have no complaints. Might be the type of material that the pad was made with.