Octalink 1 left crank keeps loosening

[silva]

A storyline included to give the context.

In order to find parts, I needed to change crankset to get another chainring bcd.
Because the bike showed a chain tension variation, II chosed for Octalink 1 system, because my previous singlespeed later fixed bike with Octalink 2 (2!) didn't have such a tension variation.
But no luck, still a variation. Likely because version 2 is one piece at one crank side so machined together, maybe easier to center.
Then the bottom bracket failed, alot play, and has been replaced by dealer by a model that required increasing the thread diameter inside the frames bottom bracket based eccenter module ment to tension the chain.
After done, subsequent weeks, months, the left crank came lose over and over again, so that I started to check after every ride and even stop during, to notice that I could retension the bolt again (big size allen key)./
Went to the dealer with it, he used a BIG allen key to fasten it, I thought solved but no, couple weeks later the crank fell again off.
The dealer upon asking did not provide a solution. So I messed on a week further, to then notice that the bolt ceased to come lose.
No idea why, it stopped without apparent reason, and it's now 9 or so months further..

Yesterday, some guy on an electric step was riding while staring straight down to his computer in the middle of his handlebars, crossed a T where I came from the right, and hit me in my side. Me and quite heavy loaded bike were thrown to the right side.
I had nothing, bike minor damage, some luggage broken but cheap 5 euro and the guy paid it.

However, an hour later, my right pedal shifted sideways alot over its axle, both pedals were worn alot, alot play, since a year, but I just keep oiling and using them, and carry spares in case. That saved my yesterday, to get back home.
Now today I decided to replace the left pedal too, and noticed that when I put alot force to tension it, my left crank moved over a short angle. The allen bolt could be tensioned a half turn further. This late afternoon after a 25 km ride, checked, could again tension abit further.
Remember, this is the left pedal, crank, NOT the side the bike fell on its side yesterday.
So I now don't know what to make of it.
Octalink is a splines shaped cross section, with a certain overlap, which is longer on version 2 than on version 1.
When the dealer loosed it completely back then, the splines showed no damage, despite crank felt off several times under heavy load, because I then didn't know what was going on, I felt something moving but kept on pushing.
So this is weird, no damage, still, the crank still losening (sometimes?).
Don't know what to make of it, I dont want to risk a damaged crank connection leaving me stuck somewhere, but the risk is unclear to me since I don"t understand what's going on here.

Clues?

 

[Cycleops]

This is a well known problem with these cranksets and was not fixed with the MkII. Shimano gave up on them and they were discontinued. When the crank becomes loose the metal spindle wears away the soft alloy crank and stops it being able to torque up sufficiently to prevent it coming loose again.
Sorry, you'll need to get a replacement, a Hollowtech or the old square taper. the former comes with everything you need including bearings , the ST crankset will need bearings and cups. You could always buy another Octalink and torque it up well but IMO its not worth it.

 

[silva]

So it's a well known problem, also a design problem,so rather bad design then, yet in mass production.
Dealer didn"t tell me, also not last year. The solution thus is dumping it, dealer said hollowtech 2 (I asked for thje same as my previous bike had since no chain tension variation) I wanted) didn"t come in a dimension (length?) I needed.
Will see what to do, having to check all the time is quite annoyant.
Still I don't get the weird go and return of the problem.
For no apparent reason, it ceased to losen, then many months later all of sudden back.
It's possible that the step hit my left crank, causing the bolt to loose tension.
Is there an ersatz solution? The bolt thread apparently disengages, what about some teflon tape?

 

[silva]

An hour ago I replaced the left pedal again, because I couldnt tension the spare I had with me properly - learnt a lesson there - the width of the tool grip section on the pedal was too small for my tool, the tool jammed itself before the pedal came under tension. So the pedal apparently made for a smaller tool, how does that rime with setting alot force?
I dumped that pedal and sorted such too small for tool models out of my stock. Design to be cheap that missed the purpose of the product? It again proves - you have to try things before relying on them.
Yesterday, about 20 km before back home, I checked the octalink bolt last time.
Today, while changing the pedal, checked again, and again could tension a half turn.
So it looks like the step throwing the bike on its side restarted this annoyancy.

 

[Cycleops]

The problem is not so much the design but the high bolt torque required.
If fitted correctly from new they're fine but once removed by someone unfamiliar with refitting, or something causes them to become loose, the problem begins.

 

[silva]

It was installed by the dealer, one he had in stock
The same dealer as the previous bikes, last one with a hollowtech 2 set.
It came lose a first time some months later.
Maybe that stock one already had that problem, by having been mounted / used before?
I don't underestimate dealers in that, many times they try to get rid of old stock and then I have to discover the why of having been in stock long time...
Today a ride, tried tensioning further 4 times, first time I could, last 3 I couldn't. Will continu do this next week. Fingers crossed lol.
Maybe that tensioning requires a kinda procedure shock / move / force / retry tensioning further.
My bottom bracket eccenter "behaves" like that. Two tensioning bolts, I search the most tension current position then lose the bolts and turn the module until abit under target tension. Then,I tension the bolts again with a force from a single finger on the end of the allen key, until I can't further that way. But if I then spin the cranks forth and back a few times, with some force, I can tension them further with the same force. And so another third, and final time. What happens there within that frame hole / clamp, might be similar to this bolt from the octalink system.

 

[keithmac]

What torque are you tightening the bolts to?.

 

[fossyant]

Octalink wasn't in production that long, it was 'rubbish'. Also more prone to folk that didn't do them up tight enough.

You tend to have lots of issues with your bike !

Square taper for the win.

 

[silva]

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/

After learning from the Rebour book and The Data Book that Gnutti had introduced a splined spindle and crankarm by at least 1948 or 1949, I searched VeloBase and found several examples of this design. From the Rebour drawing above you can see that the splined portion was nice and long, and was also spliced. I have not observed these splices on later photos of Gnutti splined spindles dating from the early 1950’s. There are a boatload of splines on this spindle, and the splined area is very long – so it does seem like a robust product, especially when compared to the Shimano Octalink V1 spindle, with its very short splines.

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

However, they, like their TDC/Williams predecessor, wore out quickly. The problem with the Shimano splined brackets--and the similar, though not interchangeable, ISIS-pattern bottom brackets made by other companies--had narrower axles and smaller bearings than their square-ended counterparts. Interestingly, Shimano's Octalink and other companies' ISIS bottom brackets had an even shorter run--not much more than half a decade--than the ones from TDC/Williams.

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.

 

[Ajax Bay]

Bottom line:
You chose to fit an Octalink 1, probably without care as it was already common knowledge that its design was flawed (as @fossyant says). Shimano brought out Octalink 2 in an effort to mitigate the flaws, without having to admit that the basic design was less reliable than square taper. I ignorantly bought a second Octalink 2 bb and 105 crankset (double) (in maybe 2016) before discovering it was not a good idea to fit it: it's still well wrapped as received (the seller must have been pleased he found a mug online).

OP: "I dont want to risk a damaged crank connection leaving me stuck somewhere, but the risk is unclear to me."
Simply replace the BB with a ST and the crankset to fit: you must have several with your history.

All your long posts, in my opinion, offer no new knowledge. I hope you find sharing your experience therapeutic. You shout at the design; you shout at the dealer. You may as well shout at the stars.

 

[fossyant]

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.

 

[Cycleops]

Bottom line:
You chose to fit an Octalink 1, probably without care as it was already common knowledge that its design was flawed (as @fossyant says). Shimano brought out Octalink 2 in an effort to mitigate the flaws, without having to admit that the basic design was less reliable than square taper. I ignorantly bought a second Octalink 2 bb and 105 crankset (double) (in maybe 2016) before discovering it was not a good idea to fit it: it's still well wrapped as received (the seller must have been pleased he found a mug online).

Maybe you could offer it to @silva as a replacement ? Thats if he feels lucky.

 

[silva]

At Ajax Bay:

I asked for hollowtech 2, reason no chain tension variation on my previous bike so thought it would solve that problem, dealer answered that it didnt come in the specs that fitted my bike and instead mounted an Octalink 1 crankset that he had in stock, that didn't solve the tension variation problem, and instead inflicted me this additional problem of losening crank.
And that's it, short.

At the time(s), I didn't know, couldn't look up things, because all dealers have done so far, is selling me stuff they wanted to sell me, things they had in stock, regardless what I asked. For ex that crankset above, upon delivery (LATE eh?) of the bike at home he told me it was a second hand he has had in stock and said he reduced my price therefore, not that I found that price as lower after looking up.
How common practice is it there in your UK, when a customer orders a crankset, to mount a second hand one, and only telling the customer that upon delivery of the bike with that crankset mounted?

Begin this week, see my topic here, I ordered SKF stainless steel bearings for my rear wheel, to replace the apparently problematic ceramic ones.
Friday a mail, already delivered and already mounted, wheel ready, the invoice, which I paid yesterday, listing "bearing 12x24x6 RVS 2RS".
RVS is dutch abbreviation for stainless steel, 2 RS stands for 2 rubber seals.
No brand, no model mentioned.
Will it be, as I asked for, SKF?
I will surely see, since I asked for spares, so I will see brand and model without dissection of the rear wheel...

 

[fossyant]

You need to learn to fix bikes yourself. It really isn't difficult. Did you get wheel fixed at shop ?.

 

[silva]

The very reason that I went to fixed gear was to be able to do drivetrain things myself, and to escape as much as possible tech, that is prone to failure, and often designed to make that sooner.
There has been a time, that when I had a flat tyre, I walked home, called the dealer to pick it up and replace and deliver it back home. Imagine haha! A "better" solution was a spare wheel, so I learnt myself how to mount/unmount a wheel. When a flat, I placed the spare wheel, and rode with the flat wheel to the dealer to replace the tyre. Also haha eh, but really, that's what I did.
To overcome more serious failures, I added a spare whole bike, so that I could continu while the broken one was at dealer for repair.
At first, several dealers, all dealers haha, a repair took 1-2 weeks. Later on months, upto 9 months, the moment that I drawed the line, enough is enough, I HAVE TO do more things myself, So, I went to singlespeed and later on fixed gear because the freewheel was beyond my capabilities.
My current bike occupied most of my fixed gear years and the drivetrain is so that I don't need special tools.
Only allen keys, and after messing round enough with the chainrings crappy bolts (I used in the beginning a metal part from a woman high heeled shoe); to try to find an alternative mounting way, and I found 1: apparently M10 bolts fit in the holes and their hexagon heads precisely fit in the space between the chainring and the spider arms of the crankset, even so tight that I don't need a second key 17 to hold the nuts.
So my drivetrain, I can do that myself, and I'm okay with that.
Beyond that, bearings etc, no, I find it too difficult, not literally, but just that it's too specialistic, too many kinds, sizes, systems.
To illustrate that: I once let the dealer that mounted the crankset I talk about in this topic, replace the bearings of my rear wheel, that was on my previous bike, bought from this dealer.
Done, I go to pick the wheel up, ask the dealer to mount it directly, with the wheel taken out then on my rear rack to ride home, he does so, I want to walk out the shop, and all of sudden that "repaired" rear wheel shows so much play that it hit the brake pads.
What had happened: the dealer had put 1 ball too much in the bearings cup; too much tension and it losed itself by just walking the bike.
And that's thus a dealer, having been 20+ years in the business. Those things are NOT easy, and for me, I have no ambition to hang out dealer myself, I have other interests, I see a bike as a thing to use, and the only reason I have some interest in the technics is to have *some* independency of people that *may* screw up their job.
I may have had bad luck, but all dealers I so far had, screwed up some jobs, some enough times that I started to wonder if they tried to mount things on my bikes just to get rid of things they had in stock and wanted to get rid of, whether they fit or not lol.
A typical such story is also of this dealer. He sold me 2 bikes that had too small frames for my posture. My feet in my front wheel when turning and handlebars too low. I asked for higher handlebars, so a longer stem. He didn't find one, for months. Suddenly he called me, he had found one. When there, it turned out to be one out of his stock, from a tandem. It was a thing with rings around the tube. He mounted it, I paid, and rode away.
1 km further, a traffic speed braker, an elevated section of the road. I bumped over it... and I had my handlebars loose in my hands. Couldn't brake, couldn't steer, I went between several cars and ended in a hedge.
Walked back to dealer, told my story, and despite me no injuries just by luck, he showed even a smile.
Just to illustrate how I lost any faith in any dealer. He removed his "solution" and put my old stem back, and I went, a failed attempt to have my handlebars higher.
The past, upto the present, was filled with such crap jobs.
Maybe I should learn to do all on the bike, but for sure, it just gets harder / more complex. See how even dealers blow it up sometimes. They DO good jobs, but they ALSO have failures.