studs -- I like to clean out the stud holes with a thread chaser, apply some blue (not red locktite) and tighten firm. Then I install the idler pulley (using red loctite) on the nut and torque the whole thing to spec. Never had an issue.
FYI - Red locktite on the nut means the stud will come out with the nut next time it needs to be removed. It's also a trick that can be used for a stubborn to remove stud if you don't happen to have a stud puller tool handy.