Octalink 1 left crank keeps loosening

[Ming the Merciless]

I see the dead horse is still being flogged

 

[C R]

I see the dead horse is still being flogged

The dead horse was exhumed, cloned and the clone slaughtered for the purpose of this thread.

 

[silva]

But the load carried needs power to move it, and that power is transmitted by your faulty crankset...
If the splines were to fail catastrophically, you might well be looking at a serious dental bill as well as a new crankset.

Hey my legs don't become stronger after I put a load on the bike, and then again weaker when offloaded. :P
The more weight on the bike, the slower I ride, and vice versa.
So faulty crankset, yes it is, from its new state already, octalink 1 is a system with a flaw and I wasn't told that.

Serious dentall bills - of course not, remember, I check the tension, and since I got some experience I immediately know what's going and I immediately stop and check tension.

11 may, as I posted here, was a restart of the problem after a heavy rain and roads partly under water.
It(s now 27 may, and since 5 days I cannot tension the crank anything further, with daily 3-5 checks.
There was a pattern in the 2 weeks with the problem - in the beginning I could tension it further quite alot everytime, and that gradually decreased, until begin last week it became zero.

In meantime I made some construction to mount low on the vertical tube to the saddle, alike a little roof, that diverts water from my raincoat sideways away from the bottom bracket area. Time will tell what that helped.

 

[classic33]

You may be cycling slower with a loaded bike, that'd be normal. But you will be putting a larger force/amount of power through the drivetrain, cranks included.

How much warning is given before a chain snaps. Often not a lot, if any.

If it's coming loose within a week, you have to consider that you may have stressed the crank arm. Every time you turn the crank, whilst it isn't fully tightened will have the crank wearing slightly. The problem grows, up to the point at which it will catastrophically fail, and the chances are you will have no warning.
It's very basic mechanics.

 

[alicat]

You do seem awfully unlucky with your components and dealers, @silva. Is your surname Worthing by any chance?

 

[presta]

Once it's been ridden loose the splines will become worn and galled, then once there's some free play in it, no amount of re-tightening will stop it from working loose again.

 

[silva]

3 further weeks later, still checking occasionally, didn't loose anymore.
No idea why it ceased losening again.
A theory might be that the spline surfaces get damaged after water seeped in and "lubricate" the contact surfaces, allowing the parts to unlodge from eachother, of after a pedal strike - a shock; and repeatedly retensioning pushes the deformed metal back in its original shape.
The problem apparently is again gone, maybe until a next heavy rainfall - riding through water.
Of course, if these parts I purchased get worn / bearings, whatever, I'll dig that Octalink system, new crankset and back to square taper.
Remember, I asked Hollowtech, and arrived at Octalink because the dealer said HT wasn't possible on the bike, and my motive was to try to get rid of the chain tension variation that I never had with the Hollowtech system on a previous bike. Octalink didn't change that, so I don't have that reason to keep buying it, and a new reason to dig it.

 

[silva]

A followup report here.
It's almost december, 6 months further, during 2 of those, retension attempts sometimes resulted in a click noise, a tick, without feeling any movement though. After that, nothing.
I put a couple rubber wraps above and around the bottom bracket, in order to keep water as much as possible away. Apparently, that was a final solution. The only case where water could get in would be wading through water deep enough to reach the bottom bracket, which is rather not common on the road.
Why I brought this up now, my rear axle and/or bearings broke up couple days ago without a direct cause, and when searching for experiences I came across
On Bicycles Stack Exchange I read this:

To solve spindle failures, Octalink was offered with bigger spindle. Unfortunately, the faulty design lacking press fit leads to left crank arm loosening and the big spindle leaves little space for bearings. Apparently Shimano uses cup and cone bearings with eighteen 1/8" balls on both sides (source).

Finally a solution was found to bottom bracket problems with Hollowtech II that moves bearings outboard so that both the bearings and the spindle can be big. It is an implementation detail that Hollowtech II uses cartridge bearings but the bearings are large (37x25x7 mm, source) so even being half complement is not a disaster, and the most of the cost of a Hollowtech II bottom bracket is the bearings so changing the entire threaded parts is not a problem.

So by trying to get rid of the big chain tension variation, with good experience on that on my older HT2 bottom bracket based bike, but which was according to the dealer not available for my bikes specs, leaving Octalink as try, I got an extra problem.

What I don't get is why they still sell Octalink BB's if they know there's a problem?

 

[classic33]

A followup report here.
It's almost december, 6 months further, during 2 of those, retension attempts sometimes resulted in a click noise, a tick, without feeling any movement though. After that, nothing.
I put a couple rubber wraps above and around the bottom bracket, in order to keep water as much as possible away. Apparently, that was a final solution. The only case where water could get in would be wading through water deep enough to reach the bottom bracket, which is rather not common on the road.
Why I brought this up now, my rear axle and/or bearings broke up couple days ago without a direct cause, and when searching for experiences I came across
On Bicycles Stack Exchange I read this:

So by trying to get rid of the big chain tension variation, with good experience on that on my older HT2 bottom bracket based bike, but which was according to the dealer not available for my bikes specs, leaving Octalink as try, I got an extra problem.

What I don't get is why they still sell Octalink BB's if they know there's a problem?

Those parts seldom fail(break up) for no reason. Poor or no maintenance can play a part though.

 

[Ajax Bay]

They still sell Octalink BBs because people have Octalink cranks they wish to use.
"Octalink 's faulty design lacks press fit": One of square taper crankset/BB's strength is 'press fit'.
Why are you not using square taper @silva?

my rear axle and/or bearings broke up couple days ago without a[n obvious] cause

FTFY Did the axle break or not?
And from another thread:

A month ago I bought a spare front wheel and its price was over 500 euro, compared to 335 euro in 2019.

You are rolling 500 euro front wheels? And Octalink?

 

[Yellow Saddle]

Peeps, don't feed the animals. They will just keep in coming back. Don't even make eye contact.

 

[silva]

They still sell Octalink BBs because people have Octalink cranks they wish to use.
"Octalink 's faulty design lacks press fit": One of square taper crankset/BB's strength is 'press fit'.
Why are you not using square taper @silva?

I said that long time ago, I had to replace the chainset due to broken crank, and I decided to attempt to get rid of the chain tension variation the bike suffers since I purchased it, by Hollowtech 2, because on an older bike, a singlespeed later on converted to fixed gear, I never had such a chain tension variation.
But the dealer said that for there were no hollowtech based chainsets compatible with my bikes BB (dimensions) and offered Octalink instead. So done, but the chain tension variation didn't go with it so failed try.
So back to square taper is fine for me, only that I will do that at an opportunity, I"m not gonna throw away things that are ok / not broken.

FTFY Did the axle break or not?

I don't know yet, dealer so far didn't report, checkup was said to be done yesterday.

And from another thread:
You are rolling 500 euro front wheels? And Octalink?

What is rolleyes about that?
Things got alot more expensive thanks to the lockdowns.

 

[silva]

The axle didn't break, and wasn't bent either, the drive side bearing showed play, so something must be damaged internally. Since the bearing (both) were new installed earlier this year, such a shoft life span, I say they are rubbish for the job, a possible explanation is being stainless, mechanical properties average around halfs steel, so I told the dealer to replace both bearings with non stainless bearings.
I left ceramic bearings due to their sudden failure - you don't see it coming, suddenly so much play that riding further is out of the quesiton.
I chosed stainless to not suffer rust, but they failed quick, yet, I could ride further home (with alot noise from the bearing itself)

And I decided to keep the axle, dealer said it rolled straight, and if the new bearings do have a reasonable life time, it will confirm the earlier SS bearings were the culprit. Because a bent axle can damage bearings / shorten their life..