Or you could say it's the manufacturing that failed.
It coincides with my experience of aluminium as a frame material. Cracks and fails.
Postby warthog1 » Sat Sep 23, 2023 2:06 pm
Or you could say it's the manufacturing that failed.
Postby familyguy » Sat Sep 23, 2023 2:19 pm
Sometimes, yes. The point, though, is that the symptom here is cracking aluminium with the root cause appearing to be the failing adhesive bond. This overloads the aluminium piece which THEN fails as the system is broken apart.
blizzard wrote: I haven't checked but almost definitely my DA 9100 cranks are in the recall. I don't really like the inspection and if everything is ok, they don't replace them. Seems like any crank in the time period could crack and just because they haven't at the time of inspection doesn't mean that they are safe. I would much prefer them to replace all affected cranks.
Postby warthog1 » Sat Sep 23, 2023 2:30 pm
If they didn't use aluminium would they be using that manufacturing process however?familyguy wrote: ↑Sat Sep 23, 2023 2:19 pmSometimes, yes. The point, though, is that the symptom here is cracking aluminium with the root cause appearing to be the failing adhesive bond. This overloads the aluminium piece which THEN fails as the system is broken apart.
Postby Thoglette » Sat Sep 23, 2023 3:12 pm
Al (like most ductile materials) has a finite fatigue life. The way Al road bike frames are designed means that the frame will likely fail “early”, particularly if ridden hard by a big, strong rider.
Postby warthog1 » Sat Sep 23, 2023 3:38 pm
I remember TLL doing that too.Thoglette wrote: ↑Sat Sep 23, 2023 3:12 pmAl (like most ductile materials) has a finite fatigue life. The way Al road bike frames are designed means that the frame will likely fail “early”, particularly if ridden hard by a big, strong rider.
Traditional Al components tend to be designed to not fail in their expected lifetime, after some bad experiences mid last century.
E.g. TooLongLegs is the only forum member I’ve seen to fatigue fail a traditional forged Al crank arm. That same crank arm in my service would a) take years to get the # of load cycles TLL does in a season and b) would likely take at least one order of magnitude of cycles to fail due to my much lower strength. So, I’ll take my entire life to fatigue my crank arms to failure whereas TLL can kill then in a season or two. His handle bars probably crack after a while, too!
Almost ever material material has a fatigue limit, it’s a question of what the designer does that determines when.
(Steel is weird, under a certain %ge load it doesn’t fatigue. Which is why we tend to make things like springs out of steel )
Postby Duck! » Sat Sep 23, 2023 5:00 pm
Only the recalled models used the glued joint. 105 and 9 & 10-sp Ultegra and Dura-Ace are still hollow construction, but a different manufacturing process. Tiagra, Sora, Claris and all non-series models are solid arms. I haven't seen enough 12-sp. to see how they're made.
Postby warthog1 » Sat Sep 23, 2023 5:36 pm
I am going off info on the ww forum. There is a thread there on it and several posters have stated the newer versions are sill glued, it may be wrong however.Duck! wrote: ↑Sat Sep 23, 2023 5:00 pmOnly the recalled models used the glued joint. 105 and 9 & 10-sp Ultegra and Dura-Ace are still hollow construction, but a different manufacturing process. Tiagra, Sora, Claris and all non-series models are solid arms. I haven't seen enough 12-sp. to see how they're made.
Postby Nobody » Sat Sep 23, 2023 7:05 pm
Manufacturers generally don't take big risk with mid to lower end (volume) products as they say there will be too many coming back.warthog1 wrote:Seems counter-intuitive they are still using it, when the "lower spec" products that carry a small weight penalty but aren't glued, haven't failed.
Postby warthog1 » Sat Sep 23, 2023 7:10 pm
Fair enough.Nobody wrote: ↑Sat Sep 23, 2023 7:05 pmManufacturers generally don't take big risk with mid to lower end (volume) products as they say there will be too many coming back.warthog1 wrote:Seems counter-intuitive they are still using it, when the "lower spec" products that carry a small weight penalty but aren't glued, haven't failed.
Postby Nobody » Sat Sep 23, 2023 8:49 pm
Postby Duck! » Sat Sep 23, 2023 9:55 pm
If true, seems like a dumb move, because it's not the left arms failing. From the pics and one in-the-flesh broken crank I've seen, the fractures propagate from the smaller bonding surfaces on the spider arms then spread down the crank. An impending crank failure should be felt by the rider, because as the bond separates the crank will bend well before it breaks entirely, and that will feel obviously weird when pedalling.warthog1 wrote: ↑Sat Sep 23, 2023 5:36 pmI am going off info on the ww forum. There is a thread there on it and several posters have stated the newer versions are sill glued, it may be wrong however.Duck! wrote: ↑Sat Sep 23, 2023 5:00 pmOnly the recalled models used the glued joint. 105 and 9 & 10-sp Ultegra and Dura-Ace are still hollow construction, but a different manufacturing process. Tiagra, Sora, Claris and all non-series models are solid arms. I haven't seen enough 12-sp. to see how they're made.
Edit had a quick look here; https://velo.outsideonline.com/road/roa ... ad-cranks/
The most obvious change on the driveside crankarm is the addition of a physical plug inside the chromoly steel spindle to keep water out. Although the shape of the crankarm is different from the Dura-Ace R9100 and Ultegra R8000 generations, the basic design appears to be otherwise unchanged.
The non-driveside crankarm sees a much bigger revision, at least for Dura-Ace. Whereas the two previous generations used a two-piece bonded construction like on the driveside, Dura-Ace 9200 reverts to a one-piece forged design (like Ultegra). Without a bond seam, there’s now no bond to fail — problem seemingly solved.
Changed non-driveside to one piece.
A plug to keep water out of the 2 piece driveside part.
Don't know how accurate that is.
Postby Tim » Sun Sep 24, 2023 7:08 am
Postby Lukeyboy » Sun Sep 24, 2023 9:06 am
Postby Retrobyte » Sun Sep 24, 2023 10:56 am
Yep - just 500gm difference. Less than the weight of the water in your bidon. I'd be perfectly happy with 105 on my next road bike, and use the saving on a wheelset upgrade.warthog1 wrote: ↑Sat Sep 23, 2023 7:10 pm
This thread made me look at the weights of 105 vs DA and Ultegra chainsets. It seems almost pointless.
https://www.cyclistshub.com/shimano-105 ... -dura-ace/
Postby Duck! » Sun Sep 24, 2023 7:39 pm
Both the 4500-odd reported failures and the total 760000 cranks stated in the articles are only North American numbers. On those figures, the failure rate is about 0.6%. Another article I read today mentioned the number of cranks affected globally could be as many as 2.8 million. What's the global number of failures? We don't know. But applying that 0.6% failure rate hypothetically suggests ≈16,800 broken cranks worldwide. Yes it's a big number on face value, but 0.6% is still a tiny proportion.blizzard wrote: ↑Sat Sep 23, 2023 9:13 amFrom my understanding is that is 4500 crank failures that were reported to the CPSC, so there are most likely a lot more failures in the field.Duck! wrote: ↑Fri Sep 22, 2023 6:19 pmAlso only TT/Tri spec 54/55T big rings.....
Seriously though, although on face value 4500-odd reported failures is a significant number, as a proportion of nearly 800,000 units just in North America, that is well under 1%. So yeah, if you have one of the affected cranks, get it checked out, but the probability of it having a problem is in reality very very low.
Postby g-boaf » Sun Sep 24, 2023 9:21 pm
Although I couldn’t resist a quip to stir people on sram, I must say the FC-R9100P “QC” that I have gave me no troubles over the huge amount of distance I did with it, and the power meter battery was very long lasting on a charge.Retrobyte wrote: ↑Sun Sep 24, 2023 10:56 amYep - just 500gm difference. Less than the weight of the water in your bidon. I'd be perfectly happy with 105 on my next road bike, and use the saving on a wheelset upgrade.warthog1 wrote: ↑Sat Sep 23, 2023 7:10 pm
This thread made me look at the weights of 105 vs DA and Ultegra chainsets. It seems almost pointless.
https://www.cyclistshub.com/shimano-105 ... -dura-ace/
Postby blizzard » Mon Sep 25, 2023 7:43 am
I suspect true failure rate is well above 0.6% as a lot of failures would never have been reported to the CPSC. Still probably only ~1% which is actually pretty high.Duck! wrote: ↑Sun Sep 24, 2023 7:39 pmBoth the 4500-odd reported failures and the total 760000 cranks stated in the articles are only North American numbers. On those figures, the failure rate is about 0.6%. Another article I read today mentioned the number of cranks affected globally could be as many as 2.8 million. What's the global number of failures? We don't know. But applying that 0.6% failure rate hypothetically suggests ≈16,800 broken cranks worldwide. Yes it's a big number on face value, but 0.6% is still a tiny proportion.blizzard wrote: ↑Sat Sep 23, 2023 9:13 amFrom my understanding is that is 4500 crank failures that were reported to the CPSC, so there are most likely a lot more failures in the field.Duck! wrote: ↑Fri Sep 22, 2023 6:19 pm
Also only TT/Tri spec 54/55T big rings.....
Seriously though, although on face value 4500-odd reported failures is a significant number, as a proportion of nearly 800,000 units just in North America, that is well under 1%. So yeah, if you have one of the affected cranks, get it checked out, but the probability of it having a problem is in reality very very low.
To those with cranks in the affected batches, get them checked and stay tuned in to any weird feel or noises, but the probability of breakage is very low.
Postby Dave_rh » Mon Sep 25, 2023 9:26 am
The glue did not fail. The aluminimum spider/crank corroded due to a galvanic reaction with the steel axle. This reaction was accelerated by moisture acting as an electrolyte.
Postby baabaa » Mon Sep 25, 2023 10:59 am
powdery aluminimum oxide
Postby jetglo » Mon Sep 25, 2023 11:28 am
Postby Snowie1 » Mon Sep 25, 2023 2:41 pm
Postby Thoglette » Mon Sep 25, 2023 2:45 pm
Got a source for that? The original bike radar piece suggests otherwise & one wonders how the surface corroded if the glue was still properly bonded.Dave_rh wrote: ↑Mon Sep 25, 2023 9:26 am
The glue did not fail. The aluminimum spider/crank corroded due to a galvanic reaction with the steel axle. This reaction was accelerated by moisture acting as an electrolyte.
The only failure of the glue is that it does not stick to powdery aluminimum oxide.
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