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i recently had a rear derailleur jockey wheel bolt come loose.

can i back the bolt out to expose some of the thread, apply the loc-tite and then screw the bolt back?

or do i have to coat the threads on the bolt, wait until dry, and then screw back in?
 

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I always apply it to the bolt and install wet. I'm pretty sure that's what the directions on the tube say to do. It seems like it would be fairly difficult to do once dry
 

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I always apply it to the bolt and install wet. I'm pretty sure that's what the directions on the tube say to do. It seems like it would be fairly difficult to do once dry
lots of bolts come with the stuff pre-applied
 

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Blue 242 or 243 - shake well, apply to clean, dry threads, then assemble and wait. It takes 24 hrs to fully cure. There are wicking types to be applied after assembly, but those are green and low viscosity. Only the tape versions are meant to be applied days before assembly.
 

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Blue 242 or 243 - shake well, apply to clean, dry threads, then assemble and wait. It takes 24 hrs to fully cure. There are wicking types to be applied after assembly, but those are green and low viscosity. Only the tape versions are meant to be applied days before assembly.
This is incorrect.

Loctite is rarely used on a bike, but where it's used we should use the right stuff. All brake bolts are fine with the medium strength, but for what we're talking about, the jockey pulley bolts, they call for high strength.

So the medium strength stuff is for caliper fixing bolts, rotor fixing bolts, brake pad fixing bolts, etc. Brake stuff. Jockey pulleys always get high strength and they're the only place on the bike that does.
 

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This is incorrect.

Loctite is rarely used on a bike, but where it's used we should use the right stuff. All brake bolts are fine with the medium strength, but for what we're talking about, the jockey pulley bolts, they call for high strength.

So the medium strength stuff is for caliper fixing bolts, rotor fixing bolts, brake pad fixing bolts, etc. Brake stuff. Jockey pulleys always get high strength and they're the only place on the bike that does.
Of course you're correct on the grade applications of medium strength (blue) vs. high strength (red). The wicking (green) stuff is used by some wheel builders to secure nipples after the build is completed.

The directions for either blue or red liquid remains the same, the selection of which should be dictated by the application, which I should have clarified. I didn't mean to imply that the OP should be using blue.
 

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There's also yellow stuff like the 641 which is required on some press-fit bottom bracket applications. I just was forced to put some on a Cervelo bottom bracket after trying quite hard to do a dry installation without any creaks. It worked.
 

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I've always just used the blue loctite on pulley bolts, and never had one come loose.

Loctite only hardens in the absence of air (weird!). So apply it and tighten the bolt. Like the other posters mentioned, it takes time to reach full strength.
 

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There's also yellow stuff like the 641 which is required on some press-fit bottom bracket applications. I just was forced to put some on a Cervelo bottom bracket after trying quite hard to do a dry installation without any creaks. It worked.
Never heard or seen of yellow Loctite. Will keep my eyes open, though. There is a purple, which is low strength.

I just recalled why I jumped on blue - it was the OP's thread title.

edit added - I just looked up 641. It's not a thread locker - it's a retaining compound made for cylinders.

BTW Loctite is a brand of Henkel, and it covers an array of adhesive-type products, not just threadlockers.
 

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I usually use Loctite 248 (blue) for medium strength and 268 (red) for high strength. This is the stick form of 243 and 263, and is much more convenient to use than the liquid forms. I rarely use 268 on bikes, I've found that 248 and proper torque usually holds fine on a most of the bicycle applications, including jockey wheel bolts.
 

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Loctite only hardens in the absence of air (weird!).
Not weird at all. The thread lockers are based on acrylics, the curing (polymerization) of which is oxygen inhibited. After you use something like 242 Blue, go back the next day - any excess squeezed out of the fastened joint will typically still be a liquid and can be easily wiped away.
 

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If it hardens on the absence of oxy, why doesn't it harden in the container with the cap on? This does not make sense.
 

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If it hardens on the absence of oxy, why doesn't it harden in the container with the cap on? This does not make sense.
There's enough air in the tube to inhibit polymerization, and the tube is somewhat permeable to oxygen. Put it in a metal tube, exclude air, and it will set up. There's actually an inhibitor in the system (usually MEHQ) that requires oxygen to work effectively.

Shipping many acrylates in rail car tanks requires they be sparged or blanketed with air to prevent polymerization.
 

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Blue will work fine for the pulley bolts. IME, those rarely loosen, even when just torqued with grease, and the extra hold with the loctite should be plenty.

I'm not sure there's anything on a bike that red loctite would be appropriate for. It's a semi-permanent adhesive, and when applied to clean parts and fully cured can't usually be undone with ordinary hand tools, unless you apply heat to break the bond.
 

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I've always just used the blue loctite on pulley bolts, and never had one come loose.

Loctite only hardens in the absence of air (weird!). So apply it and tighten the bolt. Like the other posters mentioned, it takes time to reach full strength.
Not weird at all. The thread lockers are based on acrylics, the curing (polymerization) of which is oxygen inhibited. After you use something like 242 Blue, go back the next day - any excess squeezed out of the fastened joint will typically still be a liquid and can be easily wiped away.
If it hardens on the absence of oxy, why doesn't it harden in the container with the cap on? This does not make sense.

the bottles it comes in are permeable
 

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I usually use Loctite 248 (blue) for medium strength and 268 (red) for high strength. This is the stick form of 243 and 263, and is much more convenient to use than the liquid forms. I rarely use 268 on bikes, I've found that 248 and proper torque usually holds fine on a most of the bicycle applications, including jockey wheel bolts.
I like that part about the blue stick that is it oil tolerant. I know that they make some liquid that is oil tolerant, but I could not find it in the small bottles. Those 4 oz are just way too much. I think I have had the same blue bottle for 2 yrs.
 

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641 and 609 are the retaining ones used for pf30 bb cups and bb30 bearings. Best to use an activator first then use loctite. I believe the difference between the two is how big the gap they can accommodate. These are not glue. They fill the uneven gaps in pf30 ( and bb30) shells. And they are green, not yellow.
 

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641 and 609 are the retaining ones used for pf30 bb cups and bb30 bearings. ... These are not glue. They fill the uneven gaps in pf30 ( and bb30) shells. And they are green, not yellow.
From Henkel:

Loctite ® 641™ Retaining Compound, Cylindrical bonding "
"Loctite 641 Retaining Compound is for cylindrical bonding, particularly where disassembly is required for service operations. The product cures when confined in the absence of air between close fitting metal surfaces and prevents loosening and leakage from shock and vibration. Typical applications include retention of bearings onto shafts and into housings. Recommended for maximum diametral clearance of 0.008" ..."

and


Loctite ® 609™ Retaining Compound, Cylindrical bonding

"Loctite ® 609™ is a low viscosity, rapid-curing anaerobic adhesive that augments the strength of press fit assemblies or slip fit assemblies up to 0.005"in diameter. Adds up to 3,000 psi holding power."


Both are adhesives = glue. They are for securing cylindrical parts in place, in the absence of threads. 641 is yellow, and 609 is green.
 
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