ksisler- The old bolts which fell off (Red) are definitely double allen key, I do have the chainring tool as well The new ones I am going to put on (Black) are torx at the front and allen key on the back, no sign of the usual slot on either of the bolts.


FBinNY- Are these the shoulder you mention,


I wonder if the chain rubbing (pictured) on the red chainring bolts may have had an affect on them loosening, the red bolts protruded a bit more than the stock bolts, the new black bolts will be much flatter, so shouldn't rub.