Loctite/Threadlocker
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Jay H
servicedriven.org
Excellent question !
Here is my extremely detailed OCD answer.
As a well trained master bicycle mechanic I feel qualified to answer this. I hope others find this information really useful. I too once thought nothing of using grease anti sieze compound and other incorrect chemicals on fasteners. There is more too working on a bicycle than you think many 8000+ dollar models share more in common with a race preped motorcycle than you might think.
I use blue loctite 242 (medium strength) on virtually every thing with threads. A few exceptions are threaded things that get removed or adjusted regularly. Another exception is spark plugs - I use only what is specified here cause stripping out the block on a new toyota would make me cry. I use it all over on my Car on my mountain bikes, the lawn machine ect. Here are the reasons :
1. Prevents galvanic corrosion between dissimilar metals. Its just as effective between aluminum and titanium as traditional anti seize. Yes I have a titanium mountain bike with aluminum threaded parts that thread in. Yes its even been subjected to road salts with no corrosion. Aluminum and Ti form a chemical bond really quickly and would ruin a very expensive bicycle frame.
2. Its harder to wash out than anti-sieze even in harsh marine environments. Even most solvents will not dissolve cured loctite between two fasteners.
3. Unlike anti sieze compound its relatively non toxic. - Yes my two year old niece once got a hold of a closed tube of loc-tite (242 of course) and immediately did what any two year old does and began sucking on the tube) Poision controll was very helpful to my brother and assured him that trace amounts on the outside of the container were not serious and warranted no medical attention)
4. It does not effect torque values the way that grease does. I have seen torque specifications for parts that specify two values one with grease and one with out. I have no idea how valid this point really is to be totally honest.
5. Its easy to apply and mess free. The little tube of liquid is great for small stuff, for big stuff there is a gel.
6. traditional anti sieze (copper colored goop) smells like poop. - Its also hard to wipe any mess. I am so glad to be rid of it.
7. It provides weak retention of fasteners.
Fox racing shox specifies loctite quite frequently. Its what goes inside a Fox damping unit. Nearly all top of the line bicycle parts come pre treated.
More loctite info :
First a word of caution there are many different commonly used types of loctite, misapplication will have terrible results. Some are for permanent bonds. Some are for slip fit, some are for press fit, some are for large threads, some for small. This is where most of the horror stories come from.
The blue 242 grade is not hard to break loose. If it does not strip out a 2.5mm hex headed 6000 series aluminum bolt threaded into a cast magnesium part its a weak enough bond. (yes this is a real word example - my fox racing shocks mountain bike fork employs said fasteners to hold the line to the disc brake. This is how it comes from the factory)
I would NEVER ever use it in place of a mechanical retention mechanism, like a safety wire, castle nut ect.
Loctite 242 hardens anaerobically - what does this mean. Put simply in the presence of oxygen its reasonably thin liquid. When in an oxygen free environment the stuff hardens.
The way it works is that the bits captured and compressed inside the threads of the fastener are an oxygen free environment.
To those non bicycle people this test may not mean as much - but I will try to explain enough to make my own test relivent.
When applying loctite follow the instructions. There are some grades that are not effected by grease and oil and others that are and require clean fasteners. If two parts are really hard to thread together dont grease em up and force it. The problem is likley poor machining tolerances or incompatible threads. The latter being especially true of bicycles which can have metric, english, sae and even hybrids of both.
Most cyclists now use clipless pedals, which has a sprung mechanism that clamps onto and releases a metal cleat that is bolted to bottom of a specialized shoe.
While mountain biking these bolts are subject to epic amounts of mud, salt water submersion and generally abused a lot.
Two shoes each has to bolts. One set of two bolts got loctite 242 and was torqued with a digital CDI wrench exactly to spec. The other bolt got park tools brand poly lube grease and same torque. The remaining bolt got finish-line brand anti sieze. About 6 months later when I went to remove and replace the cleats the loctive ones broke loose fairly easily. The anti sieze one took more mechanical advantage and the inside corners of the hex head were slightly rounded. The greased bolt was a nightmare, ultimately I had to drill out.
I have no financial stake in the loctite corporation will often substitute permatex or generic as long as its the proper grade.
Here is my extremely detailed OCD answer.
As a well trained master bicycle mechanic I feel qualified to answer this. I hope others find this information really useful. I too once thought nothing of using grease anti sieze compound and other incorrect chemicals on fasteners. There is more too working on a bicycle than you think many 8000+ dollar models share more in common with a race preped motorcycle than you might think.
I use blue loctite 242 (medium strength) on virtually every thing with threads. A few exceptions are threaded things that get removed or adjusted regularly. Another exception is spark plugs - I use only what is specified here cause stripping out the block on a new toyota would make me cry. I use it all over on my Car on my mountain bikes, the lawn machine ect. Here are the reasons :
1. Prevents galvanic corrosion between dissimilar metals. Its just as effective between aluminum and titanium as traditional anti seize. Yes I have a titanium mountain bike with aluminum threaded parts that thread in. Yes its even been subjected to road salts with no corrosion. Aluminum and Ti form a chemical bond really quickly and would ruin a very expensive bicycle frame.
2. Its harder to wash out than anti-sieze even in harsh marine environments. Even most solvents will not dissolve cured loctite between two fasteners.
3. Unlike anti sieze compound its relatively non toxic. - Yes my two year old niece once got a hold of a closed tube of loc-tite (242 of course) and immediately did what any two year old does and began sucking on the tube) Poision controll was very helpful to my brother and assured him that trace amounts on the outside of the container were not serious and warranted no medical attention)
4. It does not effect torque values the way that grease does. I have seen torque specifications for parts that specify two values one with grease and one with out. I have no idea how valid this point really is to be totally honest.
5. Its easy to apply and mess free. The little tube of liquid is great for small stuff, for big stuff there is a gel.
6. traditional anti sieze (copper colored goop) smells like poop. - Its also hard to wipe any mess. I am so glad to be rid of it.
7. It provides weak retention of fasteners.
Fox racing shox specifies loctite quite frequently. Its what goes inside a Fox damping unit. Nearly all top of the line bicycle parts come pre treated.
More loctite info :
First a word of caution there are many different commonly used types of loctite, misapplication will have terrible results. Some are for permanent bonds. Some are for slip fit, some are for press fit, some are for large threads, some for small. This is where most of the horror stories come from.
The blue 242 grade is not hard to break loose. If it does not strip out a 2.5mm hex headed 6000 series aluminum bolt threaded into a cast magnesium part its a weak enough bond. (yes this is a real word example - my fox racing shocks mountain bike fork employs said fasteners to hold the line to the disc brake. This is how it comes from the factory)
I would NEVER ever use it in place of a mechanical retention mechanism, like a safety wire, castle nut ect.
Loctite 242 hardens anaerobically - what does this mean. Put simply in the presence of oxygen its reasonably thin liquid. When in an oxygen free environment the stuff hardens.
The way it works is that the bits captured and compressed inside the threads of the fastener are an oxygen free environment.
To those non bicycle people this test may not mean as much - but I will try to explain enough to make my own test relivent.
When applying loctite follow the instructions. There are some grades that are not effected by grease and oil and others that are and require clean fasteners. If two parts are really hard to thread together dont grease em up and force it. The problem is likley poor machining tolerances or incompatible threads. The latter being especially true of bicycles which can have metric, english, sae and even hybrids of both.
Most cyclists now use clipless pedals, which has a sprung mechanism that clamps onto and releases a metal cleat that is bolted to bottom of a specialized shoe.
While mountain biking these bolts are subject to epic amounts of mud, salt water submersion and generally abused a lot.
Two shoes each has to bolts. One set of two bolts got loctite 242 and was torqued with a digital CDI wrench exactly to spec. The other bolt got park tools brand poly lube grease and same torque. The remaining bolt got finish-line brand anti sieze. About 6 months later when I went to remove and replace the cleats the loctive ones broke loose fairly easily. The anti sieze one took more mechanical advantage and the inside corners of the hex head were slightly rounded. The greased bolt was a nightmare, ultimately I had to drill out.
I have no financial stake in the loctite corporation will often substitute permatex or generic as long as its the proper grade.
goodtimes
Expedition Poseur
The reason that there are different torque specs for dry and wet threads, is that the tension on the fastener (and thus the clamping force between the two parts) is established by the friction between the bolt and nut (or threaded hole, as the case may be). Basically, once you get that bolt finger tight (assuming clean threads with no interference, no gap between the parts, etc), you have taken up 100% of the free play (so to speak). Any further turning of that fastener will result in the fastener stretching. That stretching is what creates the clamping force between the parts. There is a mathematical relationship between torque on a fastener and the amount that it stretches.
If you add anything to the threads that will reduce that friction (oil, grease, anti-seize, loctite, water, plating on the fastener, etc), it will reduce the amount of torque required to achieve that same amount of stretch. Remember, it is the 'stretch' that establishes the clamping force, not the torque. So, if the threads are dry and you need 75 lb/ft to achieve a certain clamping force, then you lubricate the threads, you may only need 60 lb/ft to get the same stretch (clamping force). Going to 75 lb/ft with those lubricated threads will give you a higher clamping force - which can warp parts, strip threads, etc.
This is the same reason that coarse threaded bolts have to be tightened to a higher torque value to achieve the same clamping force as fine threaded bolts. The finer thread pitch reduces friction.
Each chemical will have a different effect on the torque/tension relationship. There are some tables out there that break it down pretty far . . . but for most automotive applications, you can lump most oils and greases into one category.
** on edit - I should add that this is a very simplistic view. Lubricants (or lack there of) are just one of many factors that go into the torque : tension relationship.
Last edited:
keezer37
Explorer
Excellent! Thank you. I hate anti-sieze. I thought there was just medium and high strength Loctite.
I learned something today. In spite of all my efforts.
Jay H
servicedriven.org
goodtimes
Thanks for expanding on that. Good and logical.
The example of course vs fine threads is probably correct but I would also thought that with fine threads you would have more mechanical advantage so for a given torque at the head there is more clamping force. I have observed this with two different pullers one being high quality and built by shimano with a very fine thread pitch the other being Chinese and inexpensive with course threads requiring a lot more effort. When I think about it more it seems it would have to be the mechanical advantage, because with a finer thread 1 revolution makes less movement than with a course thread.
Sub Urban
Be careful with the stainless stuff. Many stainless bolts are not up to the same grade as there steel counter parts. Stainless alloys are generally more corrosion resistant but there often not as strong as a real high grade bolt. For any thing not load bearing its probably a good idea however. Being the bicycle mechanic that I am I am a big fan of lock nuts, that is to say using two nuts tightened against each other.
The only real disadvantage of loctite that I have observed is that you have to reapply when removing and re-installing a fastener. Of course this would true for anti sieze also.
For industrial apps you can even get thread locking tape.
Nearly all high end bicycle parts come with a threadlocking compound pre applied, which is great.
Thanks for expanding on that. Good and logical.
The example of course vs fine threads is probably correct but I would also thought that with fine threads you would have more mechanical advantage so for a given torque at the head there is more clamping force. I have observed this with two different pullers one being high quality and built by shimano with a very fine thread pitch the other being Chinese and inexpensive with course threads requiring a lot more effort. When I think about it more it seems it would have to be the mechanical advantage, because with a finer thread 1 revolution makes less movement than with a course thread.
Sub Urban
Be careful with the stainless stuff. Many stainless bolts are not up to the same grade as there steel counter parts. Stainless alloys are generally more corrosion resistant but there often not as strong as a real high grade bolt. For any thing not load bearing its probably a good idea however. Being the bicycle mechanic that I am I am a big fan of lock nuts, that is to say using two nuts tightened against each other.
The only real disadvantage of loctite that I have observed is that you have to reapply when removing and re-installing a fastener. Of course this would true for anti sieze also.
For industrial apps you can even get thread locking tape.
Nearly all high end bicycle parts come with a threadlocking compound pre applied, which is great.
goodtimes
Expedition Poseur
That would be another [completely legitimate] way to state the same thing. With the finer thread pitch, one revolution of the fastener will 'stretch' it less than one revolution of a fastener with a coarser pitch - therefor it takes less torque to turn it that one revolution.
To use an analogy that fits well on a vehicle based message board - the fine pitch threads are like a lower gear ratio. More input revolutions to get the same output, which means that less power (torque) is needed to turn the input side.
78Bronco
Explorer
Specifically a thread is a ramp wrapped around an axis. A fine thread is a long ramp with less incline requiring less force to move an object up than it would take to push the same object up a shorter steeper ramp.
We use torque values to simplify the measurement of tension but it is less accurate than the proper method to actual measure the stretch induced on a bolt.
We use torque values to simplify the measurement of tension but it is less accurate than the proper method to actual measure the stretch induced on a bolt.
Wiley
Adventurer
Ive been meaning to pick some up after my rear shock came out in Mexico which is impressive considering how long that damn bolt is, I almost lost it it was hanging by a "thread". I suspect the mechanic who added a leaf to my leaf spring may have been the problem, though I dont know why he would have touched that, so maybe it was a fluke.
seanz0rz
Adventurer
i use blue (the medium strength) on bolts that are low torque, and prone to vibrating loose.
I always try to use a locknut (steel or nylon depending on application) or a lock washer (star or split style). there are times that those options are not practical, so they get thread locker.
most suspension components get it, since they see so much vibration and movement.
I always try to use a locknut (steel or nylon depending on application) or a lock washer (star or split style). there are times that those options are not practical, so they get thread locker.
most suspension components get it, since they see so much vibration and movement.