msl109

Hi folks - have read in multiple places that cantilever brake bolts should be threadlocked to prevent the bolts from unscrewing from vibration and use. I have several questions about this, some which have been addressed elsewhere and some I haven't seen discussed. If I go ahead and do this, I plan to clean the bosses of any grease and do the same for the bolts, then apply blue threadlock to the threads before reassembling. Here's are my questions:

1. Necessary at all? I've never had an issue, but I realize that doesn't mean I won't.
2. Necessary to clean off the existing grease first? I assumed so, but I'm no chemist and have only a rudimentary understanding of how the threadlock works.
3. For the sake of corrosion resistance, do I need to make sure the threads are completely coated with the threadlock?
4. Is the threadlock really adequate to prevent corrosion?

Any informed replies, as always, are much appreciated.

​​

awac

My go to thread lock (I am in the UK, but expect the number is the same for you) is Loctite 243. You can undo it with hand tools. If you find it stiff a hot air gun can help, but really I have never had to use it on the size of bolts on a bike. The best thing about 243 is it is tolerant of mild oil contamination, so if you don't get it perfectly clean it will still work. It is called anaerobic. It remains liquid until isolated from oxygen. The adhesive completely fills the microscopic gaps between interfacing threads to positively lock and seal threaded assemblies, preventing lateral movement and protecting the joint from corrosion that can result from moisture, gasses and fluids.

Buy some, get a bolt and nut, put some on and leave it to cure. Then undo it and try it for yourself. It goes a long way and lasts well. Ciao.

Iride01 

I've never intentionally used thread locker on a bicycle. Nor have I ever replaced any existing thread locker if I ever removed and cleaned the nut or bolt that may have had some on them.

If you check your stuff often and are reasonably observant, then I see no need for it. However if you are oblivious to everything until disasters happen, then you might should use it.

awac

Iride is absolutely correct, you don’t have to use threadlock, it is a choice. I don’t use it all the time. Correct selection of fasteners, nuts, bolts, washers, regular maintenance, lubrication, protective coatings & correct torque are all that is required.
However….if I was building something that might leave my ownership, where I was not certain of how observant the new guardians of the said machine would be, or if I had a little knowledge or interest of fettling, going on a long distance ride etc, then it can be a good insurance. Oh, and if like me you work near the sea, ceramic grease and threadlock really helps with galvanic corrosion!

Try it, experiment. Then decide if it is for you or not, that’s the fun of fettling!

pdlamb

IIRC, you're supposed to clean all oil and grease off surfaces you're going to Loctite together.

That's a hassle I don't need, so when I unscrew a canti arm (happens every five or ten years), I grease the threads before reassembly and make sure the bolts are on tight. It's worked so far.

veganbikes

I mean cleaning everything and thread locking is not a bad thing but honestly cleaning and re-greasing is also fine. awac had some excellent advice though for any bolting decision.

So far I can't recall any bolts coming loose from not being thread locked and haven't had any issues with bolts that come prepared with a thread locking compound getting corroded.

FBinNY 

Screw fasteners have been in it use for over a century before adhesive threadlockers existed. Moreover, 10s of millions of bikes with cantis have been been sold and used for decades without thread lockers.

So the answer to the first question should be obvious. The tension within the a properly tightened bolt, and friction alone is more than enough to keep it in place. IF they loosen, it's a slow process, an occasional eyeball will spot problems in time.

The above notwithstanding, some prefer the added security an adhesive may provide. If so, I prefer flexible friction types like Vibra-tite to adhesives.

awac

“Screw fasteners have been in it use for over a century before adhesive threadlockers existed” does Linseed oil count? Helps lubricate a bolt thread on assembly and then dries locking the thread. That is an interesting thought, what is the oldest threadlocker? Must go to the vaults….

FBinNY 

Yes, I'd count linseed oil, and others that act similarly. There are also a variety of things that work, including intentionally distorting a section of the threads to cause some binding.

FWIW I appreciate the value of thread lockers which add a degree of functionality not available in certain situations. Anyone who's been turning bolts long enough remembers when adjustment screws all used stiff springs to create load and maintain position.

maddog34

i tear down about 100 bikes a year.. i assemble about 100 bikes a year.. most have no locktite on the brake bolts.. occasionally i run into one WITH locktite on the brake bolts... The Brake pivot Post usually comes out of the frame and remains in the brake arm..... the brakes are then a hassle, not an asset.

NEVER use Red Loctite or Green Loctite* on a bicycle... Blue is the Glue for You.

*some exceptions may apply

zandoval 

My GrandPa used to keep a little bottle of Shellac in his tool box for thread locking. My Dad had a little bottle of Nail Pollish, and I have a small tube of Blue Loctight... Seldom used but there just the same...

drlogik 

I don't use thread lockers all that much but when I do, on a bike, I use Vibra-Tite VC-3. Why? Well, unlike most other thread lockers (e.g. Loctite, Permatex, etc) it does not harden. It's remains malleable. Why is that important? Because fasteners don't get "locked" on the part to the point that they are difficult to remove like other thread lockers that actually harden. A hardening type thread locker can also cause stripped fastener heads trying to remove them...been there more than a few times. What this means is you can remove the fastener and re-install and you'll still have a fastener that won't back out from vibration. It's good stuff.

I have virtually stopped using hardening thread lockers on all fasteners for other non-bike applications and use Vibra-Tite VC-3 instead. If I have a high temperature application then I go with a "Blue" (medium strength) thread locker.

.

Ross200

What was that white stuff that came on the mounting bolts of those "millions" of Shimano cantis back in the day? Suntour-blue or white? I don't think it was cocaine although maybe that would keep the bolts tight?

FBinNY 

Yes. OEMs will often use a form of preapplied thread adhesive on screws.

Consider their situation. Shimano makes the brakes, but has no control over what happens after they ship. They can't insure that xyz bike company has decent process controls when they mount the brakes. However, if anything goes sour, guess who gets sued.

But let's not confuse legal CYA with practical necessity. There's no denying that thread lockers provide more margin for error, but that doesn't make them necessary, nor are they a substitute for skill or diligence.

msl109

I have blue threadlock but I think it's another brand. I'll have to check out whether it's the same because I really don't think it will be easy to get the bosses completely free of the old grease with anything that's paint safe and from the other posts here, I'm beginning to doubt I need it at all.

msl109

I had the thought as well that it's legal CYA. Thinking a properly torqued bolt, especially with the serrated washers this brakeset came with, designed to avoid loosening, should be enough.