Yes flutes that is it. Heh I was talking about using lube BEFORE you break them not after you broke them already haha. I already went through about 5 problems like this on my 66 and broke a bolt off in the caliper (the only bolt that holds the caliper on) Well lets put it this way...There is still no bolt in there. After that I learned to take more time and lube the bolts (rusted ones) up really good, let em sit, lube them again and tap the screw, bolt, whatever with a hammer and THEN go at it.