Octalink 1 left crank keeps loosening

[Ming the Merciless]

You must be the unluckiest cyclist in the world, with all your travails.

 

[classic33]

@silva, learning from your mistakes is how you learn to do things correctly.

 

[craigwend]

I have no torque displaying key, after the problem first appeared I looked things up and read high torque needed, so I pushed as hard as my allen key (normal length) allowed. The first key I used apparently was rubbish since its hexagon head got torsed due to it, a second key didn"t show that.
As said, when I went to the dealer with it, he used a mega size allen key, never saw such a big one, think it was 40 cm long with some thick grip. Yet it came lose again, although with a longer period between, to then after a week messing around retensioning it, without apparent reason stay fixed, until now the step hit.

The step hit me in my left middle, maybe its front wheel hit the left crank, causing it to start loosening again.
Maybe the very beginning of the problem was caused by a pedal strike (fixed gear setup is more prone to this)
Causing a deformation somewhere on the spline shape, giving some play that then increases itself.
Such scenario could also explain why at some point it xeases to lose again, the metal of the spline edges getting deformed back close enough to eachother, ending the play.

That latter is then abit similar to the square taper principle, as proved after a crank break, I had an older crank in my shelf, from another make crankset, and I had to tension it further, in the beginning even with just a couple streets riding inbetween, the periods got longer and longer, until the crank ended fixed on the taper. Likely the alu of the different used before - crank got deformed, and had to be deformed towards the other square taper axle.
The least one can say with such a scenario here, is that octalink 1 is a vulnerable mechanical connection.
A shock is enough to damage the splines. Square taper being more robust.

I found this article: https://restoringvintagebicycles.com/2017/03/14/a-brief-history-of-splined-cranks-and-spindles/

... and a link there to https://midlifecycling.blogspot.com/2013/01/another-forerunner-to-shimano-innovation.html

So the why looks like again being (cheaper) design towards faster wear / less robust due to smaller surfaces / less material, to sell more replacements.
Also proved by the first Octalink bottom bracket - after a mere year the bearings wear gave enough play to force replacement. My previous bikes each got a new bottom bracket once in their 10 years usage. This is tenfold lol.

Well if nothing else I've learned my very late 70's early 80's Shimano Splined misadventure was the 'Selecta' after returning / having it replaced many times on the none drive side crank with the spline made of putty gave up and got a nice shiny square taper Suggino one...

Amazing how often the square wheel is reinvented even when it doesn't work...

 

[Ajax Bay]

@silva, learning from your mistakes is how you learn to do things correctly.

That's one way to learn. Far better dividend for effort is learning from other people, including their mistakes.
To learn lessons from their own mistakes and challenges @silva might keep a 'lessons identified' log, consider what change might be needed to learn each lesson, make that change, record it, and aim to avoid repetition.
I also recommend the OP seeks advice from others as to 'good practice' and recommendations for 'dealers' aka LBS that they (friends, say) have found reliable. Virtually CycleChat might offer the first (but the OP would probably need to morph to a 'they likely know what they're commenting about' approach).
Is the OP's adoption of eccentricity (bottom bracket or elsewhere) the best option for their skills.
Square taper ftw. Lubrication ftw.

 

[silva]

You must be the unluckiest cyclist in the world, with all your travails.

Luck had little to do with it, just that dealers try to get rid of their existing stock, that failed to sell, usually for a reason, and that I was too easy, causing them to pass these to me.
So I ceased to behave easy, and no regret so far, rather the contrary, my own choices so far allowed me to get back home by DIY.
That story about that rear wheel bearing having 1 ball too much, that was in a spare wheel, and when ready, and I came at the dealer to pick it up, in a past, I would have taken it, put in on my rear rack and ride back home to keep it as spare, so that in case of problem, I put the spare in.
Imagine what would have happened if I had done that. I would suffer a defect wheel in the bike, put the spare instead, with a ball too much, and the bearing would be pushed open, and I would have 2 unusable wheels, leaving me with no bike to ride.
Instead, I asked the dealer to mount the wheel immediately, because I didn't trust him.
Well, the error, the defect, manifestated itself already in the shop eh, saving me from discovering it in the ugly situation.
Why I then didn't trust the dealer: because of earlier experiences. That loosening stem being one, but the direct earlier story was my first bike convertion singlespeed > fixed. The dealer had removed the freewheel, mounted a cog, and had used some aluminium ring with holes drilled in it, as a kinda mockup spacer.
I took the bike, jumped on it, pushed with my right leg, and alot noise did the chain make. That alu ring was already broken by just pushing once on the pedal. Way too weak to withstand the force, mostly due to those holes (ment for mounting bolts through them?) drilled in it, the ring had broken at one of these.

See, it's not that I suspect bad things, that I have a pessimistic nature or so, it's that I've SEEN things go bad, due to badly done jobs, done badly for whatever reason including just getting rid of an old stock item.

 

[silva]

Stop messing and get a new crankset. SJS Cycles and Spa stock loads. Once its come loose, its probably damaged some splines, so will happen again.

The weird thing is that at some point, the crank ceased to come lose.
Yesterday and today, no further retensions possible.
Maybe my repeated attempts to tension it further, tensions it enough to not start losening anymore.
The allen bolts of my rear cog and the bottom bracket eccenter also "behave" like that, I have to retension several times and then they stay fixed. Also pedals, I replaced both in recent week, and both could be further tensioned a couple times, and now not anymore.

 

[Ming the Merciless]

Luck had little to do with it

Clearly not, or else we’d see a decent number on here also posting about similar experiences. That says you are making your own problems in some way. You need to figure out what you are doing differently; that you have these never ending convoluted problems one after the other.

 

[Ajax Bay]

If, after riding a few days on installed pedals, you can 'tighten them further' "a couple of times", the pedals weren't tightened properly in the first place. What is the mechanism (bearing in mind the threading direction) which would loosen properly torqued pedals. From memory 30-40Nm aka firm push on a 14" spanner.

 

[fossyant]

The weird thing is that at some point, the crank ceased to come lose.
Yesterday and today, no further retensions possible.
Maybe my repeated attempts to tension it further, tensions it enough to not start losening anymore.
The allen bolts of my rear cog and the bottom bracket eccenter also "behave" like that, I have to retension several times and then they stay fixed. Also pedals, I replaced both in recent week, and both could be further tensioned a couple times, and now not anymore.

You aren't tightening them up enough.

 

[silva]

I tighten as much as I can with the allen key.
Every time.
First times bolt moves, then it doesn't.
Checked today 2 times, bolt didn't move.
So apparentlty, it needs a certain amount of tightenings, to stop loosening.
Remember I said that the first time the problem occurred, the dealer used a very big allen key to tighten it. Way bigger / 5 times longer than my small key.
Despite that, it STILL came lose again.
So I again tensioned it, bolt moved, 3 or 4 times spread over days, then at some point couldn't move the bolt anymore.
Until that step hit me, and it started losening again.
Apparently, the same repeated tensioning attempts solved it again.

 

[classic33]

Threadlock time?

 

[Cycleops]

Youre wasting your time Silva, once the spindle has worn the cranks that's it, they will tighten again but always work loose. Please, for all our sakes just get another crankset.

 

[silva]

I don't like threadlock, see it as an ersatz methoI to make up for design faults.
It may solve problems, but when you have to lose it on purpose, it makes it harder.
For ex my rear cog with 6 bolts on a brake flange, a rear cog is something that quite often needs to be unmounted/remounted (ex to flip) and my bike was delivered with a dot red locktite on the thread of those bolts, I managed to unscrew them, alot force, was unware of it, and bolts were also hard to turn back in.
I don't trust it then anymore, if they already are hard to turn upon new mounting, what will it be after so much months in the dirt?. Instead of forcing them back in, I decided to tap the thread of the flange out, then the bolts went well in, and never had a problem with that.

 

[classic33]

I tighten as much as I can with the allen key.
Every time.
First times bolt moves, then it doesn't.
Checked today 2 times, bolt didn't move.
So apparentlty, it needs a certain amount of tightenings, to stop loosening.
Remember I said that the first time the problem occurred, the dealer used a very big allen key to tighten it. Way bigger / 5 times longer than my small key.
Despite that, it STILL came lose again.
So I again tensioned it, bolt moved, 3 or 4 times spread over days, then at some point couldn't move the bolt anymore.
Until that step hit me, and it started losening again.
Apparently, the same repeated tensioning attempts solved it again.

How did the step manage to hit you?

 

[silva]

Youre wasting your time Silva, once the spindle has worn the cranks that's it, they will tighten again but always work loose. Please, for all our sakes just get another crankset.

When I went to the dealer at the first occcurence of the problem, and he used that big key, he dismounted the crank completely, and I didn't see damage / signs of wear on the surfaces / edges of that splined end.
I think that the problem with the design is that a shock (pedal strike for ex) causes a movement strong enough to make the bolt turn a little bit, and that any little bit suffices to progressively increase the play.
Why else would the crank sitay fixed for so many months? Remember, it hasn't been removed by me, the splines within the crank mate with the same splines of the axle so it's not like some lucky position.
It's only the very first time (surprise to me, that's why, that the crank really disattached, and at the dealer.