Copper grease and thread lock compound. Now, you can dismiss 🙂 Or, if you want to know why you need them, stick with me a little longer.
If you have a look at the image, you’ll see an ordinary socket hexagon bolt. If you look closely, you’ll notice a tiny hole in it, indicating that it’s not a standard item.
I’m writing about this because something similar happened to my car. I replaced the suspension arm bushings and removed the caliper completely to make work easier. I wasn’t too concerned about the tightness of the caliper bolts while mounting it back on because I knew I’d be removing them soon to replace fender flares. However, because the lower bolt was not extremely tight, it fell off, causing the caliper to move, making horrible noises, and scoring the rim. The lesson here is to keep the caliper bolts tight. However, for bikes, don’t push it too far: caliper mounts are aluminum and easily strip off.
That’s why we have another strange thing on these bolts: that blue thing: I’ve seen those before, almost always on genuine Japanese parts for marine engines and even cars. Thread lock is often used on such bolts. It bridges the gap between the hole and the bolt, making the bolt more difficult to slack off due to vibration…
When I worked in a marine engine shop, we used locking compounds almost liberally and religiously…funny to have those two words in the same sentence, but true: strangely, they make bolt removal easier because salt water does not penetrate and promote galvanic corrosion, resulting in a bond that is almost as strong as welds, if not stronger (or worse, for my side of view).
What is thread lock?
A thread lock or thread locker is a kind of adhesive. I use the green one for marine engines because it’s almost watertight. They are sold in very small containers, the ones I use was smaller than a
chain lube bottle which is considered “huge”. I kept them in a refrigerator, because the instruction manual says they need to be babied, and they were expensive as hell. A 50ml Loctite is typically 30$ now in here, but I remember it was much more expensive 20 years ago. It was only Loctite that was making them, but now there are plenty of manufacturers. The man who invented them was also the founder of Loctite.
They come in various colors; I’ve seen purple, red, green, and blue. Purple is really weak stuff, blue being medium, green is typically having blue ones strength but flows excellently, while red is effectively a superglue, but can be removed by heat: I am not sure if heat destroys it or make the hole larger and break the bond, but it works. (as aluminium hole expands more than the steel bolt under heat). A few years ago, I bought a very cheap, dubious chemical from AliExpress ago, which worked quite well after all the years and terrible storage conditions.
How to use thread lock?
The strange thing about those thread lock applied bolts: thread lock stays liquid when there is air; it cures in the absence of oxygen! So when you apply it, do not wait for it to cure. It won’t: just screw it in, and it will set in 24 hours.
Never use red compound, or any color advertised as “permanent”: they are not really permanent, but you’ll need a big heat source to remove them, which will damage your component, or at least, the paint. Use a blue one. One added benefit of thread lock compound is, it also slows galvanic corrosion, AKA welded bolts.
Don’t forget copper grease!
Copper grease is even more magical for a mechanic than a thread lock: I use teflon tape, even some low-strength adhesive in the absence of it, but copper grease has no match! Problem with bikes is, they use a lot of different aluminium alloys and steel. Steel is a fairly reactive metal, and aluminium is very reactive: this match leads to a galvanic corrosion, sometimes “effective” as welding, which is not a good thing for us. Copper is one of the least reactive metals of all, and it’s alternatives are gold, platinum, which is more expensive than gold, and pretty much nothing else.
Copper grease is grease with copper particles in it. It is a barrier against galvanic corrosion. It’s not just for steel to aluminium contacts, but also must be used on aluminium to aluminium contacts too, as aluminium alloys are all different and prone to stick together pretty badly.
When buying copper grease, stay away from no-name brands and dubious sellers, as copper is the new gold now. Expect to pay around 50-60$ for a kg.
What copper grease is NOT?
Copper grease was originally intended to work in high-temperature environments as it can withstand 1100 c – but for bikes, consider it as a “mounting paste”. Never use copper grease on bearings! Do not use copper grease as a carbon fiber paste replacement – copper grease is corrosive to epoxy, and carbon fiber paste has tiny plastics instead of copper.
Copper grease -or copper paste- does not replace grease, carbon fiber paste, or thread-lock compound. Their area of application may seem tiny, but especially for bottom brackets, it’s a must. You’ll know when your square taper bottom bracket does not move! Yet, it’s no fire and forget solution, too. It’s only good for half a year, maybe a year at best, depending on salinity, weather, mating metals, and of course, the quality of copper grease.
Get a decent, preferably a kg of copper grease, you won’t regret it – there are various and effective ways to save from fluids, but that is not it.