Shimano Crankset recall: bonded Hollowtech ones

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silva

Über Member
Location
Belgium
The "natural" protective oxide layer is formed extremely fast (some hundreds of pico seconds) and is very thin (4 nano meter).
So it appears almost impossible to do something on the "bare" / native alu. I think I once read about using some acid treatment to avoid that natural layer being formed, in order to treat the bare material.
From what I remember from a work, an anodisation layer is some hundredfolds thicker.

About the U cross section, the video from Hambini or so, shows two U shapes, one narrower, one wider, shifted inside eachter, forming a closed rectangle with two double sides the overlap), the mating surfaces glued, although the glue appears everywhere there, even on the inside where no surfaces mate.
One may wonder, there has to be some tolerance, between the narrower and the wider, to give the glue some space to be there / some thickness for strength of bond. Now, the glue has probably different mechanical properties than the aluminium U profiles, causing torsion forces to be able to act differently on one U shape than on the other, causing the U profiles to undergo stress between eachother, with the glue having to absorb the torsion difference, which may cause it to detach gradually, especially, and first, at an end of the double profile, the crank basis due to the highest leverage there, as also sketched by Hambini.

About glue and water, and maybe eventual galvanic corrosion (but that would dissolve and I don't see powder in the video), normally, the glue should keep water out. Glue can withstand water when it can dry out again, it's when long time wet that
glue fails and I don't think that water can permanently stay in a crank since it goes up and down / inverted position, in the case of an entrance for water.

It would be interesting to see the internals of a replacement crank/spider, to compare these with the faulty, the differences may give a clue on the cause of the losening.
 
OP
OP
Ajax Bay

Ajax Bay

Guru
Location
East Devon
Interesting video by 'Peak Talk' showing incipient failure well before actual and a look at the replacement chainset received.

View: https://youtu.be/fFOXkyOvs9Q
 

silva

Über Member
Location
Belgium
In that video it's said that the replacement is "alot heavier". No figures given, and easy to miss since it's the last sentence.
Assuming same material kinds, heavier means more material. Thicker parts. How does that fit in the corrosion explanation for failure?
 
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silva

Über Member
Location
Belgium
What's your experience with these types of cranks @silva ?
That a chain runs on a hollowtech crankset without a tension variation and on a Santos TM3+ not.
Never had problems with cranks except Stronglight on the latter bike, with both cranks breaking at the pedal eye, the right one some weeks after the left one.
When replacing that crankset, I thought lets try Hollowtech maybe i get rid of the tension variation on this bike too but wasn't available for the required specs and dealer threw me to Octalink 1 (he mounted it without asking saying anything), whose left crank kept on losening, a pain in the !ss for about a year until I noticed a correlation with rain/water. I mounted covers over the bottom bracket and the left crank ceased loosening. I still have the long hex key in my bag, remembering the days that I had to stop every so many km's to retension the crank, with wet days bringing that pester back for a couple weeks everytime.
The hollowtech bike is now my spare bike, used very seldom, since I started to do some things myself instead of bringing to dealer and walk back and forth..
Or are you an ST 'inboard' bearings man?
Not sure how to grasp the question, hollowtech is outboard bearings and all the rest inboard, I think? At least, that was a notable difference between that bike and I all others I had. I think outboard bearings are better, bigger section of the axle supported, less leverage, also outboard = more room so bigger balls / bearings = wear more distributed = longer in service.

Given his previous posts, zero. :whistle:
Should I quote you my posts about hollowtech bike without chain tension variation?
A tension variation on a fixed gear is a pester when having to retension the chain to compensate for wear, and also when resisting pedals to slow down. It's like a "dead band", the cranks move but wheel doesn't yet.
 

fossyant

Ride It Like You Stole It!
Location
South Manchester
That a chain runs on a hollowtech crankset without a tension variation and on a Santos TM3+ not.
Never had problems with cranks except Stronglight on the latter bike, with both cranks breaking at the pedal eye, the right one some weeks after the left one.
When replacing that crankset, I thought lets try Hollowtech maybe i get rid of the tension variation on this bike too but wasn't available for the required specs and dealer threw me to Octalink 1 (he mounted it without asking saying anything), whose left crank kept on losening, a pain in the !ss for about a year until I noticed a correlation with rain/water. I mounted covers over the bottom bracket and the left crank ceased loosening. I still have the long hex key in my bag, remembering the days that I had to stop every so many km's to retension the crank, with wet days bringing that pester back for a couple weeks everytime.
The hollowtech bike is now my spare bike, used very seldom, since I started to do some things myself instead of bringing to dealer and walk back and forth..

Not sure how to grasp the question, hollowtech is outboard bearings and all the rest inboard, I think? At least, that was a notable difference between that bike and I all others I had. I think outboard bearings are better, bigger section of the axle supported, less leverage, also outboard = more room so bigger balls / bearings = wear more distributed = longer in service.


Should I quote you my posts about hollowtech bike without chain tension variation?
A tension variation on a fixed gear is a pester when having to retension the chain to compensate for wear, and also when resisting pedals to slow down. It's like a "dead band", the cranks move but wheel doesn't yet.

You seem to ride 'cheap end bikes' given your posts. Have you any bikes that use the current Dura Ace or Ultegra cranks ? My bikes use the old stuff that is solid alloy, Dura Ace and Ultegra/600 - but you seem to be offering advice 'googled' ..we can all do that..
 

fossyant

Ride It Like You Stole It!
Location
South Manchester
That a chain runs on a hollowtech crankset without a tension variation and on a Santos TM3+ not.
Never had problems with cranks except Stronglight on the latter bike, with both cranks breaking at the pedal eye, the right one some weeks after the left one.
When replacing that crankset, I thought lets try Hollowtech maybe i get rid of the tension variation on this bike too but wasn't available for the required specs and dealer threw me to Octalink 1 (he mounted it without asking saying anything), whose left crank kept on losening, a pain in the !ss for about a year until I noticed a correlation with rain/water. I mounted covers over the bottom bracket and the left crank ceased loosening. I still have the long hex key in my bag, remembering the days that I had to stop every so many km's to retension the crank, with wet days bringing that pester back for a couple weeks everytime.
The hollowtech bike is now my spare bike, used very seldom, since I started to do some things myself instead of bringing to dealer and walk back and forth..

Not sure how to grasp the question, hollowtech is outboard bearings and all the rest inboard, I think? At least, that was a notable difference between that bike and I all others I had. I think outboard bearings are better, bigger section of the axle supported, less leverage, also outboard = more room so bigger balls / bearings = wear more distributed = longer in service.


Should I quote you my posts about hollowtech bike without chain tension variation?
A tension variation on a fixed gear is a pester when having to retension the chain to compensate for wear, and also when resisting pedals to slow down. It's like a "dead band", the cranks move but wheel doesn't yet.

The whole post is bollix.
 

silva

Über Member
Location
Belgium
You seem to ride 'cheap end bikes' given your posts. Have you any bikes that use the current Dura Ace or Ultegra cranks ? My bikes use the old stuff that is solid alloy, Dura Ace and Ultegra/600 - but you seem to be offering advice 'googled' ..we can all do that..
You seem to ... (1)
Some figures for you:
The Hollowtech2 based bike was 1200 euro somewhere in the late 200x, brand .
The current travel bike (see my avatar) was 4300 euro in 2017.
Blame the price?

You seem to ... (2)
"Offering advice googled", yes duckduckgo of course, most ppl aren't born knowing that fire is dangerous and that there is such thing as a bicycle.
 

silva

Über Member
Location
Belgium
The whole post is bollix.
The Hollowtech based bike never showed a chain tension variation.
The avatar bikes square taper and also now Octalink 1 does, with the original stainless steel chainring from brand Surly, and with all subsequent Velosolo ones, both 48T and 47T.
Upon advice from Yellow Saddle, years ago now, I measured a Velosolo chainrings centering, along a brico way - drawing it over on paper, then draw lines between the edges of the holes of the mount, then again lines from their crossing points, and so on, and I ended up with a small well centered hexagon, determined as such by drawing a pixel in its center and measure back to the holes. There's a post about it somewhere here.
The variation causes a tension variation of about 2 cm up and down play;
With my original 48T/16T config, the variation gradually grew, upto the point that i couldn't tension the chain properly, had to tighten it too much in order to prevent the most hanging position risking the chain falling off.
After some duckduckgoing I discovered that this was due to 48/16, which was about a worst case wear concentration scenario.
I solved it, and that was the reason too, by going to 47/16. No integer division result / prime numbers.
Later on I discovered another benefit of that change: my tyre got a bigger number less worse skid patches instead of a couple severe worn.

What the cause is of the variation, remains a guess, it has always been that 2 cm up and down, with all parts of various brands and various specs.
I consider it a problem since it's an asymmetrical wear cause, resulting in load concentrations instead of for ex more teeth distributing the load.
 

silva

Über Member
Location
Belgium
Maybe it was inspected by a hammer blow.
It's okay Joe it doesn't separate, next!
Inspection of something with a design flaw is like a weather report.
The next hour, day, week, month, year can be entirely different.
 

wafter

I like steel bikes and I cannot lie..
Location
Oxford
That's like saying my cars brakes are fine they passed the MOT 5 months ago. Alot can happen in 5 months..... I was still married!😢🤣

Indeed.. tbh they should all be recalled regardless of whether they show any outward signs of failure.
 
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