Cracked DA 9000 and Ultegra 8000

Discuss light weight issues concerning road bikes & parts.
Cemicar
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by Cemicar

kgt wrote:
Fri Jul 05, 2019 11:49 am
Campagnolo cranksets are as stiff, lighter, sexier and without creaks and cracks.
Not sure they're lighter. I know they include bearnings, but even titan axels SR cranks weigh 20 or 30 grams more than DA... And their 4-arms cranks look just horrible IMO.

by Weenie


GothicCastle
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by GothicCastle

kgt wrote:
Fri Jul 05, 2019 9:47 am
I had asked that before: why doesn't Shimano go for carbon cranksets to solve such issues? I am really curious.
For the shape of a crank arm and the kind of stresses it takes, carbon doesn't have a clear advantage over forged aluminum.

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kgt
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by kgt

Maybe it has. I have never heard of a Campagnolo carbon crankset cracking out of the blue.

BdaGhisallo
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by BdaGhisallo

kgt wrote:
Fri Jul 05, 2019 11:49 am
Maybe the guys at Shimano 'feel' that alu cranksets are better, but obviously they are not. Campagnolo cranksets are as stiff, lighter, sexier and without creaks and cracks. I am sure that a huge company like Shimano can start produce carbon cranksets next week if they want to.
And that's the beauty in all this - if one doesn't agree with Shimano's stance and prefers a carbon crankset, one is always free to spend their monies elsewhere.

GothicCastle
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by GothicCastle

kgt wrote:
Fri Jul 05, 2019 1:25 pm
Maybe it has. I have never heard of a Campagnolo carbon crankset cracking out of the blue.
It is a good thing that manufacturers don't base their designs on whatever anecdotal evidence you might have "heard."

TheKaiser
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by TheKaiser

kgt wrote:
Fri Jul 05, 2019 9:47 am
I had asked that before: why doesn't Shimano go for carbon cranksets to solve such issues? I am really curious.
Many carbon cranks have had their fair share of problems. Sram and Easton/Raceface have had a lot of the aluminum pedal thread inserts break loose, particularly on the MTB models.

Having said that, Campag might have a better system, so I'm not going to imply that they have the same issue. I know I have seen some carbon cranks that use an aluminum spine that joins the pedal thread and BB spindle interfaces, rather than using a separate bonded insert in each spot, which seems like it would be more reliable, although probably heavier.

TheKaiser
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by TheKaiser

ooo wrote:
Thu Jul 04, 2019 3:14 pm
try 105 cranks (5800,r7000) they are hollow forged like 6700.
6800,9000,r8000,r9100,m9100 are hollow bonded, glued:

viewtopic.php?f=3&t=143022
Thanks for that breakdown. I wasn't sure when the Ultegra construction style switch happened. I've always wondered why shimano didn't try to improve the hollow forge process further to use on the high end stuff, rather than going bonded, but I guess it must just be too difficult to get that big an open cavity without going to the 2-piece glued design.

TheKaiser
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by TheKaiser

Greatestalltime wrote:
Thu Jul 04, 2019 3:04 pm
I’ve cracked my cranks on two different bikes a week apart. They are both right at one year old. DA on a Protos and 8000 on an Advanced SL. Both 172.5. Both at the same exact place on the crank about 1.5 inch from the top, right by the print. The cracks are both on the drive side and identical in every way. Except on the 8000 a large wobble accompanied the pop every down stroke.

They also both occurred at the same place. A walking/riding bridge that crosses the Ohio River. I’m guessing 8-10% grade, but may be way off. I sprint up both sides nearly every day. Usually in 52/16 or 17. I will take some pictures, but the bike shop gave me a loaner 6700 while they work on the warranty. I purchased them both from Merlin.

The guys at the shop said they’ve never seen it. Is this common? My 6700 had around 50k miles was a 170mm and I never had any problems at all.

Thoughts/ advice. I’d there a stronger crank? Should I modify how I ride? I really like attacking this this hip the way I described.
Man, what are the odds on that! 2 cranks, a week apart, on the same hill! I guess if that is your main high power hill jam spot it makes some sense, but still the timing is pretty amazing.

Not sure if you have seen it, but there is a bike blogger who has a very complete post on this topic as he suffered a crash as a result of this type of break. There are also some good comments from others who had the same problem, and there is a lot of Shimano shaming: http://carlinthecyclist.com/epic-failur ... eed-crank/

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cveks
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by cveks

Friend told me that guy I know from local bike club also cracked his Ultegra crankset today

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kgt
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by kgt

GothicCastle wrote:
Fri Jul 05, 2019 4:30 pm
kgt wrote:
Fri Jul 05, 2019 1:25 pm
Maybe it has. I have never heard of a Campagnolo carbon crankset cracking out of the blue.
It is a good thing that manufacturers don't base their designs on whatever anecdotal evidence you might have "heard."
Maybe some of them already base their designs to my evidence, you never know ; )

Greatestalltime
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by Greatestalltime

Thanks Kaiser, checked out that blog and that picture is exactly where both of my cranks cracked. I guess I’ll have to start inspecting that spot. I’m clearly lucky mine happened so gradually. I guess it’s just poor quality control on some of these cranks or it would be happening to more riders. Though, I had two different models and both went bad.
Last edited by Greatestalltime on Sat Jul 06, 2019 12:46 pm, edited 1 time in total.

XCProMD
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by XCProMD

GothicCastle wrote:
kgt wrote:
Fri Jul 05, 2019 9:47 am
I had asked that before: why doesn't Shimano go for carbon cranksets to solve such issues? I am really curious.
For the shape of a crank arm and the kind of stresses it takes, carbon doesn't have a clear advantage over forged aluminum.
That’s debatable. Shimano has to resort to make the cranks hollow to remain competitive in stiffness/weight towards cfrp. Then they need to glue two shells. And it’s clearly not working. Furthermore, alu is very sensitive to fatigue. Any stress riser around the spider/spindle will kill the crank. This has always been cause of (not very frequent, true) failures.

With carbon there’s the insert problem but Campag has pretty much nailed it. Difficult to see loose inserts even in more than 15 year old cranks (I’ve only seen a first series Record among the many hundreds bicycles I’ve worked on).




Inviato dal mio iPhone utilizzando Tapatalk

Greatestalltime
Posts: 63
Joined: Sun Jul 02, 2017 12:47 pm

by Greatestalltime

So I’m guessing the countless pro teams using DA get a higher quality crankset. Are they forged or glued?

After two failures I’m getting skeptical about the quality of the design.

BdaGhisallo
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by BdaGhisallo

Greatestalltime wrote:
Sat Jul 06, 2019 12:50 pm
So I’m guessing the countless pro teams using DA get a higher quality crankset. Are they forged or glued?

After two failures I’m getting skeptical about the quality of the design.
What's the rate of failure, though? How many DA and Ultegra cranks do you think are out in the wild?

I doubt Shimano is making a special higher quality crankset, and only giving it to pro teams. If Shimano found a way to improve the current design it would likely be too costly to do it for such a small quantity and they would put it into production to prevent consumer crank failures if the problem was really that widespread.

ooo
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by ooo

It looks like in most/all cases da/ultegra fails on right crankarm. Shimano can fix this problem by using spiderless (direct mount) design

For the 1st glued mtb crankset FC-M9000 shimano used hollow bonded (glued) design on left crankarm only (right crankarm was hollow forged).
Newer FC-M9100 have both crankarms hollow bonded (glued) + direct mount chainring (no spider, left & right crankarms are almost the same).
'

by Weenie


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