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FSA crank bolt won't stay tight

Old 05-21-13, 08:06 PM
  #1  
zacster
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FSA crank bolt won't stay tight

I've probably posted this question before, but I'll ask again. How do I get the crank bolt to stay tight on my FSA SL-K Mega-Exo crank? Last year when tightening it on the road I actually broke the bolt. The replacement from FSA just doesn't stay tight. I've used a torque wrench on it a few times, but I don't carry that on the road, but it hasn't helped in any case. I tightened the bolt last night for a quick 15 mile ride, and when I went out again tonight my crank arm was ready to fall off again.

Should I try Loctite? And which one? Should I try some kind of lock washer? I know the later models came with a wavy washer, but when I asked FSA they said that my model doesn't take one. There's also the issue with the self-extractor. Since it is also normal threaded it will come off with the bolt, and I lost the original. The later model reverse threads the self extractor.

And a different issue, but also with the crank I think. I bought a derailleur alignment gauge and I used it and now the derailleur is straight and parallel as it should be and is quiet, but I get a lot of chain chatter on the crank. What's the best way to quiet it down? The gear is Chorus 10, except for the FSA crank.
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Old 05-21-13, 08:11 PM
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Usually, when a crank bolt won't stay tight, the problem is actually elsewhere.

If there's any crank to spindle play the crank creeps forward and back, and will thereby walk the bolt loose. Odds are that the first time the bolt loosened, and before you noticed, the loose crank wore and developed play, and once having done so the battle was lost.
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Old 05-21-13, 08:23 PM
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Contrary to what FBinNY said, FSA have had issues with their crank bolts on their MegaExo cranks. You need to use some 242 Loctite(blue).
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Old 05-21-13, 08:28 PM
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Originally Posted by linus
Contrary to what FBinNY said, FSA have had issues with their crank bolts on their MegaExo cranks. You need to use some 242 Loctite(blue).
This doesn't counter what I said, it reinforces it. Bolts don't magically work loose. There has to be some movement under them to provide the action that loosens them. If a crank is rock solid and stationary on a spindle, the bolt won't ever loosen.
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Old 05-21-13, 08:41 PM
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FSA used to pack a small tube of assembly compound with some models of cranks. Don't remember which models off the top of my head, but it was Loctite 641, to be applied to the crank spindle interface, not the bolt threads.
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Old 05-21-13, 10:31 PM
  #6  
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It appears that FSA themselves recommend using 641 on the model crank that I have. I guess I'll give it a try. And yes, it is to the spindle interface, not the bolts.

If this doesn't work I'm getting a different crank.
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Old 05-22-13, 09:31 AM
  #7  
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They started shipping them with Loctite after having to replace tons of them under warranty (mine included - after 250 miles). If it has already come loose, the interface is probably already shot and you won't get it to function properly.
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Old 05-22-13, 03:31 PM
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Hi,

FWIW I toasted my left crank - it just wouldn't stay tight.
It had got loose and was clearly damaged from being loose.
Tightening the nut just didn't work, quickly came loose.

Cheap bike so I went for a cheap solution. Cleaned up
the worst of the damage on the crank with a file and
used a small amount of two part epoxy as a filler
and threadlock*. Worked a treat - its now fine.

rgds, sreten.

*
To be precise I tightened up the nut and then took it off,
and applied further epoxy into the corners of the bracket.

I was going to leave it like that to set but noticed I'd
got some epoxy onto the castelled surface of the
washer integrated with the nut, so I thought sod
it and refitted the nut tight before it all set.

So not really used as threadlock, but similar.

Last edited by sreten; 05-22-13 at 03:44 PM.
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Old 05-22-13, 04:16 PM
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Originally Posted by FBinNY
If a crank is rock solid and stationary on a spindle, the bolt won't ever loosen.
Hi,

And its the damage from being loose - ridges in the corners -
that prevent it being rock solid, and precession undo's the nut,
however much you tighten it, it won't be enough to stop it.

Unlike pedals the left crank is not reverse threaded - I don't
know why, and unlike the right crank which is barely stressed
for drive torsion as that goes through the chainwheels, the
left crank has to take the full drive torsion to the chainwheels.

rgds, sreten.

edit :

I've just realised that both crank BB interfaces are almost
completely stressed rotationally by only the left power stroke.

So the right has a harder time than I intimated, but the big
difference is precession will tend to tighten the right side.

Last edited by sreten; 05-22-13 at 04:48 PM.
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Old 05-22-13, 04:58 PM
  #10  
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Buying the bike but then having them install this crank is one of the few things cycling related that I've regretted. My original crank on the original frame was a Chorus 10sp cartridge/square taper type. And if it's toast as everyone seems to be saying, I don't want to buy another FSA, but I don't want to replace the MegaExo bearings. I'd have to have a shop do it as that's a little beyond my capability and toolset. I can pack a loose bearing BB and have it smooth as buttah, but while cartridges are supposed to be easier, I never quite get them right the few times I tried (headset, wheel bearing).

And doing a little research in BBs and cranks can give you a headache these days with all the standards. There are so many "standards" that they're not standards anymore. I guess I have a threaded shell which can take thread on cartridges, whether ISIS or Mega or whatever, but not BB30? And the bike is a Kuota, which is "designed in Italy" but made in Taiwan like most carbon bikes. Does that mean I have an Italian threaded shell?

Last edited by zacster; 05-22-13 at 05:04 PM.
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Old 05-22-13, 05:10 PM
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Hi,

Currently toast does not mean its not fixable. You can file the crank
back to perfectly useable in combination with the Loctite. IMO not
addressing any current damage is a head in the sand attitude.

rgds, sreten.

For using a file on toasted cranks it is very easy to make it better
and very hard to make it worse. The ridges, which are the problem,
however inept you are will go first and that is all you need to do.

Last edited by sreten; 05-22-13 at 05:25 PM.
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Old 05-23-13, 01:51 PM
  #12  
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My FSA Comet does the same thing. I snugged it up until the side to side play went away, after applying blue loctite. (I've ridden a Triumph Bonneville since 1987 so I have a big bottle.) So far, so good. The torque spec is very low, and my torque wrench isn't accurate at those levels. Aluminum bolt into aluminum threads = caution.

I'm looking for an excuse to get a SRAM crankset with a lower granny gear, anyway.
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Old 05-23-13, 02:04 PM
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Originally Posted by linus
. . . . FSA have had issues with their crank bolts on their MegaExo cranks. You need to use some 242 Loctite(blue). . . .
Also on some of the MegaExo cranks like mine the bolts are simply too short -- they don't utilize anywhere near all the available threads in the aluminum. By custom cutting a pair of (longer) replacement bolts I was able to engage at least 7 more threads total as I recall. Also did the Loctite. Never once a problem nor the whole time since.

Might just go out and do a 1000m climb this afternoon on said crank.
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Old 05-23-13, 05:40 PM
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same issue with my FSA Gossamer Mega Exo. I DNF'd a race this year because of it so I tossed it in favor on a 6700 crank. Used locktite for the install just to be sure and its been rock solid ever since.
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Old 05-23-13, 09:13 PM
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FSA answered my question and also said to use Loctite on the THREADS, not the spindle/arm interface. It can't hurt at this point and maybe will save me a few hundred dollars for a new crank.
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Old 05-23-13, 09:32 PM
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Originally Posted by zacster
FSA answered my question and also said to use Loctite on the THREADS, not the spindle/arm interface. It can't hurt at this point and maybe will save me a few hundred dollars for a new crank.
Don't use 641 on the threads though. 242 or 243 for that.
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Old 05-24-13, 04:50 AM
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Originally Posted by Dan Burkhart
Don't use 641 on the threads though. 242 or 243 for that.
They said "the blue stuff", which I think is 242. I have a tube of 262, which is used for Velomax/Easton wheels to lock down the double threaded spokes in the hub so they don't turn while you adjust the spokes at the rim.
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Old 05-24-13, 04:54 AM
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Originally Posted by zacster
They said "the blue stuff", which I think is 242. I have a tube of 262, which is used for Velomax/Easton wheels to lock down the double threaded spokes in the hub so they don't turn while you adjust the spokes at the rim.
Yes, blue is 242. 243 is the same strength, just formulated to tolerate some oil.
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Old 10-06-19, 02:04 AM
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Are there any decent retaining compound alternatives to Loctite 641 for non-drive spindle interface bonding?

Last edited by ctak; 10-06-19 at 02:06 AM. Reason: keyword addition
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Old 10-06-19, 07:03 AM
  #20  
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After years of dealing with this crank (I'm the OP from 2013!) I replaced it with a Chorus Ultra Torque crank last year. I got my use out of it and didn't feel like it was worth even trying to replace with another FSA. I put new bearings on a used ebay Chorus and new cups and have no problems at all with it.
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Old 10-06-19, 10:34 AM
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Originally Posted by zacster
I guess I have a threaded shell which can take thread on cartridges, whether ISIS or Mega or whatever, but not BB30? And the bike is a Kuota, which is "designed in Italy" but made in Taiwan like most carbon bikes. Does that mean I have an Italian threaded shell?
Doubtful. Italian threads are rare these days.

FSA has a bottom bracket compatibility chart for their cranks. Here's the section that shows 68mm English threaded shells and MEGA EXO cranks:

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Old 10-06-19, 11:41 AM
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Originally Posted by terrymorse
Doubtful. Italian threads are rare these days.

FSA has a bottom bracket compatibility chart for their cranks. Here's the section that shows 68mm English threaded shells and MEGA EXO cranks:
Long ago resolved. This thread is from 2013. It is an English threaded BB and I replaced the BB/Crank last year with Chorus. I wasn't going the FSA route again. What made it especially easy to go from FSA to Campy is that they both use the same BB tool, and UltraTorque is really easy to install.
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Old 10-06-19, 01:14 PM
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Originally Posted by zacster
Long ago resolved. This thread is from 2013.
Ha! I have to start looking at the dates on threads.
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Old 10-06-19, 05:28 PM
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Yea, I auto-subscribe to threads that I start or reply to, and I saw someone had replied to it the other day to get it going again.
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Old 10-06-19, 06:49 PM
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Nice move

Originally Posted by zacster
After years of dealing with this crank (I'm the OP from 2013!) I replaced it with a Chorus Ultra Torque crank last year. I got my use out of it and didn't feel like it was worth even trying to replace with another FSA. I put new bearings on a used ebay Chorus and new cups and have no problems at all with it.
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