loctite on bottom bracket?
 

early this week I started hearing a creaking noise coming from the bb area, and since I don't have the proper tools to check it myself I took it to my lbs.

To make a long story short, they tightened the noticeably loose bottom bracket on both sides. Afterwards they mechanic suggested that if the creaking returned to bring it back so they can throw some loctite on the threads. And of course after about 20 miles, the creaking came back...not so loud this time, but its definitely there

My question..... is that a good idea?

I have heard of that being practiced. I know some people that put Loctite on lockrings whenever they install them (example, on the bottom bracket or fixed-wheel cogs).

A good mechanic would know how to first check if the BB faces are square to the threads and if needed, face the BB shell. A hack would use loctite and ignore the real problem.

Is it a cartridge BB, or what? We aren't mind readers! :)

If it is, the creak may be coming from inside the left side cup, between it and the BB shell. Take out the BB and grease between the cup and BB shell.

You don't have a loctite problem, you have a friction problem.

I would never, personally, use Locktite on a bottom-bracket. Regardless of the type - square-taper, cartridge, or external. Nor would I teach others to do so. If there is one very good - IMHO - thing that stands out with the new external bb's, it's the resurgence of the practice of 'facing' the shells.

Its a shimano deore lx, so its a cartridge with square tapered type bb in a steel frame.

I must admit that I have no idea what it means to "face" the bb shell. I will ask the guys at the shop if they checked to make sure it was square.

If they did square the face and tighten it to torque specs, and its still creaking what should I do next?

^Teflon Tape/plumbers tape.

In general, thread locking compounds are not a good idea, especially on threaded joints that are preloaded (ie torqued to some ft-lb spec). Actually, I grease my BB threads (somewhat the opposite of a locking compound). I assume the shop is somewhat competent and can torque the BB cups to specification. As Sci-Fi suggests, teflon tape may help.

Thanks for the info

X2 on the grease. On my last frame I used teflon tape, and it worked great. On my newer frame, the tape was making it difficult to install the bb, therefore I used grease only for the application. I even grease the crankset bolt, even though the LBS recommended I loc-tight it. I ensure the right amount of torque on the bolt, and I have never had a crank arm come lose on me. Then again, I'm pretty anal about maintenance - every bike gets stripped, lubed, and screwed, every year. Things rarely come lose :love:

If the threads of the bb shell were damaged when the bb first became loose, loctite will help keep it in place. You want to use the lightest available. I think the purple is the lightest. The blue will work as well, but will make it extremely difficult to remove since the bb threads have so much contact area (large diameter, fine pitch threads). The idea of locking compounds being a bad idea is pretty much nonsense. When you are installing the fastener, the locking compound will act like a lubricant, letting you torque the fastener to the right specs. Once it cures, it will help keep the fastener from loosening. A properly torqued fastener shouldn't loosen, but damaged threads, poor tolerancing, vibration and installation mistakes can all effect a fasteners ability to hold. Loctite is a nice safety measure.

I'm not saying there's never a need for Loctite, or that one or another of the range of Loctite products can't solve certain problems. But, these days it seems that Loctite is being used a substiture for skilled mechanical work, the same way that plastic wood is the hallmark of poor cabinetry.

Find a mechanic who'll make a definitive diagnosis of the problem before admisnitering the latest cureall.

"Facing" the shell is usually done immediately after tapping/chasing the threads. Either a pilot sleeve or the taps themselves are used to align a cutting tool than ensures that the outer edges ("faces") of the BB shell are precisely perpendicular to the BB thread axis. If this is not done, the BB bearings will either bind or be loose at some point in the rotation cycle.

FWIW Shimano preps all their bb cup threads with loctite that I've ever used, and I've used a lot of Shimano bb's...square taper, octalink, external...maybe they don't know what they're doing :rolleyes:. Mixing grease and loctite compounds isn't necessarily a good idea. Sometimes a little extra thread filler other than loctite can work via teflon tape. YMMV.

I think we're getting off track here. Ryanwood has stated he has a Shimano Cartidge BB. His frame does not need to be faced. Cartridge BB's are kind of idiot proof, as long as you have the proper threads, install it with the proper torque on the DS, moderate torque on the non-DS and you're good to go. The left side cup really does not need to be torqued as tight as the DS, not even close actually. I've experimented with both, and the left side cup doesn't move either way.


Shimano has some gray stuff on the threads of the cups, and inside the non DS cup. I wouldn't call it loctite, it's more of a filler.

**On the inside of the non DS cup is where it's most prone to creak.**

No one thinks to grease it because the gray stiff is there and when it's new it feels pretty snug, so who would think you need some grease in there? You do, it's almost a sure bet it will creak eventually because the gray stuff breaks down. When my UN-72's started to creak, I took them out, and low and behold, the inside of the non DS cup was bone dry, Aluminum cups rubbing on steel. Creak creak creak. :lol: a bit of grease in there and creak was gone.

As bikinfool stated, teflon tape makes a great filler for threads instead of loctite. You can mix it with grease even and when you install the BB you can see all the pretty colors mash together as some gets squeezed out.

Wrong. You can't "prep" a BB with loctite. You can preapply some other sort of thread locking material, but it's just a gap filler, not an adhesive like loctite.

Using a cartridge BB does not eliminate the need for BB facing. A face that's very far off square can still cause the bearings to bind and the right side to loosen. Most frames these days are adequately machined at the factory, but the paint should still be removed from the right face of the shell.

You can check if facing if needed by screwing the right cup in until it contacts a .010 inch feeler gage and then use .008-.012 inch feelers to check for high or low spots. I consider this a must with outboard bearing cups. None of my three LOOK frames needed facing.

A lot of antisieze compounds are grey in color. I use the Park Tool antisieze myself (and it is gray).

My bad, should have said thread locker of some sort....Loctite's a specific brand in any case (none of their industrial products fit the bill?).

Loctite, depending upon the version, fulfills multiple roles. The lighter-grade stuff isn't so much of a bonding-agent as it is a gap-filler.

What's happening with the OP's bike is that the already-large clearances between the BB and shell may be a little more than normal do to manufacturing tolerances and/or too many thread-chasing operations. Facing a BB ensures proper 90-degree squareness between the lockring-face and the spindle-axis. This does help lock the BB in place... laterally.

However, it does nothing about vertical movement. When you tighten the BB into the shell, the threads are pulled laterally into each other and the tension/stretch of the threads provides friction between the threads that keeps it in place. But the vertical gap, the difference between the ID/OD of the thread is still present. Then with vertical forces from pedaling, the BB will move up and down, grinding the threads against each other and cause squeaking.

This is where a gap-filling compound comes in handy. Grease sometimes works for small tolerances. But if you've got larger gaps, then a hardening compound that solidifies to fill the gap works better, such as Loctite 272 or the grey stuff that Shimano uses. It's the gap-filling function of Loctite that we're interested in, not its adhesive properties.

That's also why teflon-tape works as well, you just need to add as many layers as needed to completely fill the gaps between the threads. I've had BBs where 4-layers of teflon-tape still causes squeaking, while 6-layers is too thick to thread on. Then 5-layers is the perfect amount to fill the gaps.