Loctite on caliper brakes
 

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:
115/53

Green:
90/310

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)?

Info appreciated.

You shouldn't have any problem with the blue stuff. Just use the appropriate torque on the parts.

I use blue on everything and haven't had any issues with it.

You're thinking too much. Grease bolt, torque. Done. If you are going to use blue, don't overdo it.

And don't use green for threaded parts. It's primarily designed for PRESSfit (bearing sleeves, headset cups etc) parts.

The two weakest Loctite grades are 222 (Purple) and 242 (Blue). You could use either. Do not use any of the various Green or Red grades as they are too strong and/or not intended for threaded fasteners.

That said, I've never used Loctite on any brake installation and never had the fastening bolts come loose.

+1

I don't understand why Shimano has to recommend this, liability issues?

Thanks, guys. A bit of blue 242 or none at all. If I use any Loctite when I put on the brakes on it will probably depend on whether the stuff's in arm's reach or not.

Just for ref:

This is from Park's Big Blue Book of Bicycle Repair, talking about caliper brake mounting on braze-on studs:

"Use a mild thread-locker inside the fitting and install the bolt to a relatively low torque."

Just sayin.

Are you sure this applies to caliper brakes? It sounds like the installation recommendation for cantilever or V-brakes. Caliper brakes don't mount on "braze-on studs".

Blue Loctite is a mild thread locking agent.

There is a green threadlocker (as opposed to the green 609/690 that you refer to) that is intended to wick into preassembled fasteners. I don't think it's super strong.

I agree with the others though, you don't need threadlocker on brake mounts, it's over kill. Just tighten it properly and it won't come loose.

Yes, you're right. The book goes straight from cantilever to caliper brakes. Just thought (incorrectly, it seems) that Loctite on one called for Loctite on the other. You guys set me straight.

Cheers.