Loctite and CF frames with press fit BBs.

[trailgumby]

Hi all (and hopefully Duck!). I have a mate (yes, really ) who replaced his botttom bracket bearings about a year ago with some schmick aftermarket units, and was told by the distributor to use a bearing seating loctite to fit them and stop movement in the frame.

I thought the advice sounded reasonable, as in a previous hobby racing nitro powered model sports cars it was a very common thing to do when it wasn't a cold shrink fit, albeit usually metal bearing into metal bearing seat

The problem is he has just sent me a photo of the bottom bracket shell with a radial gap in the BB shell, leading into a crack extending up the seat tube about 1cm and then at right angles around the outer circumference a short distance either side a centimeter or so in a kind of "+" shape.

I'm very concerned the loctite might have damaged the resin and made the shell brittle and cumbly. I don't know the loctite number.

Am I panicking needlessly or is it possibly an issue?

[10speedsemiracer]

Too many variables and unknowns. Which loctite compound (680..641..609?) and does the frame in question have a non-cf shell insert?

[lone rider]

Whether you use Loctite or not, the bb or crankshaft not sitting perfectly square in the frame is the cause of all problems. I doubt that Loctite has made the frame brittle but if it has it should be visible, more likely something is out of whack and because the bearing cant move due to the compound, the stress being caused has made its way to the frame. This could be manufacturing issues with any of the parts, quality of the build/right tools used.

[Tim]

I use Loctite 609 Retaining Compound for fitting and securing BB30 bearings. However, this is a metal to metal application (CAAD9 BB30 frame).
I use Loctite 243 Threadlocker for certain threads on all my bikes.
There are dozens and dozens of different types of Loctite. Some of them, especially the "superglue"-like ones could no doubt damage a plastic/epoxy surface. I would hope the distributor recommended the correct product. There is a Loctite retaining compound specifically for plastic to metal applications (I don't recall which). That aside, I'd doubt the Loctite would damage anything much more than the mating surface. Epoxy is mighty tough and (relatively) chemically resistant.
It sounds more so to me that your mate has damaged the BB shell either banging the bearings into place with brute (hammer and socket) force or has pressed one or both bearings in cockeyed and damaged the shell. That, or the frame has just failed at that point for no apparent reason other than carbon fibre just does occasionally.

Edit; "failed at that point for no apparent reason" and all of the reasons lonerider above has stated.

Can we see the photo?

[Tamiya]

Also how tight were the factory bearings & how did he get them out??
Not unknown to damage bearing seats at extraction, or scratch the CF
causing weak point for cracks to start from.


Raced nitro 1/8 onroad & off-road for years plus a dabble in 1/5s... don't recall needing Loctite bearing glue there gallons of Loctite threadlock for sure - when built to "enduro" spec. Anaerobic threadlock also takes time to cure, 8hrs to overnight is best. Loctite'ing screws in the pits just minutes before starting engine is an exercise in futility; a solvent type gooey threadlock will survive your race better. Also most Loctite is released by heat, so any ain't much good anywhere near hot engine or exhaust.

[macca33]

Not sure why someone advised loctite in a carbon BB shell ..... or, am I missing something?

[Duck!]

It's mechanical brutality, not chemical reaction that has caused the damage.

[trailgumby]

OK, I have some feedback. My mate reminded me the loctite was used on the crank spindle, not the BB shell, so I was having a seniors moment.

To answer duck's question, I don't think it was, he went to considerable lengths to get the right tool and I was there when it was fitted. No brutality was applied, quite the opposite in fact. The bearing was a firm but not a super-tight fit.

The good news is the bike shop reckons its clearly a warranty claim and will be going in to bat for him with the distributor. They could just be managing customer relations, but it's a good start.

[Duck!]

Why was Loctite used on the crank spindle?

For future reference for anyone else playing, frame manufacturers recommend using grease for PF bottom brackets, so you CAN extract it with relative ease and minimal risk of damage when it needs to be replaced.

I recall one instance where some peanut had glued in the bottom bracket, and when I went to knock out the stuffed unit, it took the factory bonded-in aluminium sleeve out of the frame with it! I did manage to fix it, but not without a great deal more farting around than should have been necessary.

[Ivanerrol]

There are only a few variations of Loctite that can be used with carbon fibre. The chemical composition of most variations reacts badly to the components in the carbon layering.
This variation - Loctite 638 - is used in automotive transmissions. Doesn't alter carbon fibre properties and is resistant to oil. Speciically designed for bearings.
This is the stronger version. However can be knocked out when required by a normal B.B. removal tool. Use sparingly on the top of the bearing - not on the Carbon frame. And .... It's normally not cheap