Shimano's blue threadlock on UN300 BB
 

Just got a new Shimano UN300 bottom bracket and wondering what to do about this hard dry blue stuff filling about half the thread depth of the non-drive ring. Probably threadlock, but it's thick and hard and looks like it's going to make threading the ring into place more difficult than it would otherwise be. And it's not even on the full depth of thread. Shimano's installation literature makes no mention of this blue gunk and says to grease the threads. So why put it on at all? To at least have something on one side of the bb if it gets installed dry straight out of the box? It seems like half of a half measure and not helpful at all to the careful mechanic.

I'm used to greasing both the bb threads and the cup threads. In this case, with aluminum threading into steel frame, considering anti-seize or fresh liquid threadlock. It makes no sense to put grease or anti-seize over dry threadlock, so should I just clean this stuff off, assuming limolene, paint thinner or acetone will have adequate bite.

https://cimg2.ibsrv.net/gimg/bikefor...968c5f6f3c.jpg

Do what you want to make yourself comfortable but Shimano's pre-applied threadlocker is looking out for the "shade tree mechanic" in my opinion, giving him/her some corrosion and thread locking protection in case they would install it as it came, dry. Other companies are doing this as well.

As noted, Shimano, and others, figure it's better than nothing. I ignore the factory threadlocker and, in the past, greased or anti-seize coated the threads on all bottom bracket cups no matter the material of the cups or the frame. An even better alternative to grease is plumber's Teflon Tape. Two layers over the threads on each cup gives a completely waterproof and corrosion proof seal that will not come loose if torqued properly.

Leave the threadlock alone. Use grease always, anti-seize if you prefer. Threadlocker and anti-seize are not opposites. They compliment each other in this case.

Shimano knows what it's doing.

Shimano tells you what to do if you want to go by their advice. And not one word about scraping off the blue stuff. So don't scrape it off....

https://cimg9.ibsrv.net/gimg/bikefor...72400de3fd.png


These are the DM's Shimano links to from their BB-UN300 product description

https://si.shimano.com/en/pdfs/dm/FC...002-17-ENG.pdf

https://si.shimano.com/en/pdfs/dm/MD...001-06-ENG.pdf


I'm also in the camp that views anti-seize interchangeable for grease when used on surfaces that don't move during normal operation. IE: screw threads. If using nickle anti-seize, don't get it on your clothes. It doesn't wash out!

Claro! A dab of assurance by Shimano. Just ignore and proceed as usual with grease or anti-seize.

I view the grease or anti-seize as necessary to keep the mating threads from corroding together and also helps with assembly. The thread lock (blue is usually considered serviceable locking, opposed to red permanent locking) helps keep the threads from rattling loose. So as mentioned above, they compliment each other. I've never used thread lock in BB threads, and if properly torqued, you won't need thread lock.

Why only 1 side?
It seems if it was such a good idea, they'd coat both sides????
Steel or aluminum BB shell?

Because the other side has a shoulder that locks the threads.

The OP said it's a steel frame.

Something to keep in mind is that there are two main types of thread lockers.

One is an adhesive, like Loc-tite and others. These may be the liquids people are familiar with, or preapplied as a microencapsulated 2 part compound, which is activated on assembly.

The other is a semisoft friction product that acts like a Ny-lock to bind the thread against vibration without gluing it together.

It's important to know the difference since the former requires a clean thread to work properly.

Fortunately, you don't need to be an expert. Shimano clearly instructs you to grease, which implies the blue stuff is the second kind.

Doesn't the non-drive side bottom out, internally, against the spindle bearing shell? I should think that side effectively locks its threads just as the drive side does (with the shoulder flange).

It should, but that end always feels kind of rubbery to me. Either because of the engagement shape or the materials. That cup is also frequently plastic, so maybe Shimano just uses threadlock as a hedge against people tightening the left cup as if it was one of their plastic ones.

Not always. Depends on cup design, shell width variance, and depth of threading

It is interesting that Shimano seems to have left out what to do with the non-drive side cup. Even in it's current General Operations DM. https://si.shimano.com/en/pdfs/dm/GN...001-26-ENG.pdf

I wouldn't think it'd get torqued to the requirements stated for the drive side. And I'd probably just run it in till flush or it met significant resistance, compensating of course for the blue stuff that is going to give it a certain amount of significant resistance.

Maybe it does get that much torque, but with the BB shells I've had, it seems some might screw in way too far. I'm just glad in my bike DIY history that I went from a cup and spindle BB straight to the 2 piece cranks with external cups.

Whether wrong or not, I'd still ride the bike and if issues show up, figure them out at that time. No worry that that my bike will blow up and wipe out half of creation with it.

That manual has nothing about any sort of threaded BB.

Sure they do. Just about as much as they did in the other manuals I referenced in the other reply I made. Shimano doesn't give in depth discussions of good maintenance practices or such. Even these DM's while more detailed than the SI's and other documents, are more just a work card for someone with a basic skill set in bicycle DIY already.

https://cimg0.ibsrv.net/gimg/bikefor...b0f8889984.png
https://si.shimano.com/en/pdfs/dm/GN...001-26-ENG.pdf

The NDS cup doesn't do a whole lot other than center and support the NDS, so torque requirements aren't a big deal. With the plastic cups you couldn't put a whole lot on them anyway

I didn't realize "chainwheel installation" was BB installation.

However, the instructions say use grease and list a tightening torque. There is nothing about BB depth because it assumes the frame is the correct type for the BB being used, and the chainline should be 100% if you selected the right parts and the frame is in-spec.

I've never seen a problem in 30 years installing of this kind of BB in shops.

And I'm sure they probably work well for a long time whether you grease the threads or not. The OP shouldn't worry too much about doing the most perfect installation ever. Just put it in and ride, if issues happen, then figure out why and they'll know better next time.

I thought like you too when I didn't see the threaded BB in the TOC of the manuals, but they did specify press fit BB!

The question of whether or not to grease BB threads or not isn't critical for most people. However for those who ride in the rain it can easily become critical. Dry threads tend to wick and trap water leading to corrosion problems. Keep in mind that water doesn't always enter from the outside. It often enters at the seat tube and dribbles down into the BB where it stays a while doing it's damage unseen.

BITD as a Campy service tech I'd often get severely corrosion damaged BB cups. Customers weren't happy when I showed them that the cause was within the BB and not water that was entering from the outside.

It would be foolish to not use grease on a metal cup. It will seize.

Thanks all.

Got the Phil grease out of the toolbox, buttered the threads in the frame and the threads of the bb, including the blue stuff. Made the install. Piece of pie [cake]. 66 Nm with the torque wrench, which felt remarkably easy. A tiny bit of clean up (glad I didn't use anti-seize). Drive side threads were much easier to engage perfectly square after I started the non-drive side a few turns first so it could support the main assembly in proper alignment.

BTW...:)

http://www.the-whiteboard.com/scraps/scraps007.gif