Yesterday I took a stock Caliper Bracket Pin out of a caliper bracket that I took off of a street car that has never been remaned. When you loosen the pin in the slightest, the amount of "play" in the threads between the bracket and pin is quite eyebrow raising. When you go to tighten, even when you finger tighten the pin, there is still a (at least what I would consider) large amount of play as if there is too much tolerance in the threads.
Whenever I get calipers from a reman, I pull the pins out, clean both threads, then red loctite, and install. After every session at Road America I pull off the calipers and try to see if I can wiggle the pins. I have had pins come loose following this procedure.
Waiting for Bench Racer to chime in here.
Adding to what One (inside comment) referenced:
Referencing Tyler's pictures:
It's the upper rear caliper bracket bolt which fails/fractures, correct.
Ask yourself or check the thread internal and external threads dimensions (even when using red Loctite). Are these thread quality for a race track rumble strips or for a grocery getter?
Check the distance from the bolt seating surface where the bolt breaks.
Check how far the bracket first full thread is from the bolt seating surface.
Check the bracket mounting surface for the failed bolt.
Check how much of the failed bolt seating surface seated on the bracket and observe the bolt undercut.
As yourself, why does the lower bracket bolt with the same size threads not fail/fracture? The thread is 9mm x 1.25 pitch.
The bracket and bolt metal makeup and toughness and hardness also play a roll in the bolt fail/fractures.
Theses are clues to think about to as why the bolt fails/fractures.
Happy 4th to all.