I'm putting Ultegra BR-6500 brakes on my Specialized Roubaix frame. Every source I've consulted says to use a low-strength thread lock on the brakes. Problem is, finding a low-strength thread lock is next to impossible. For Loctite, it would be the purple (rated 222). The blue stuff (rated 242) is everywhere. So should I just go with a bit of the blue stuff, which I already have, or maybe even the green penetrating type, or nothing at all? Here are some torque specs for the blue and green type:
Blue torque strength ("break/prevail"), in inch-pounds:
The green type is recommended for "preassembled" parts, so I'd put the brakes on then apply the Loctite. Also, the green is recommended for parts that are 2.2-12mm in diameter.
I'm leaning toward using the green Loctite. It's rated a "medium-strength" threadlocker, but isn't it a bit weaker than the blue (looking at the torque specs above)?