FAILURE Shimano Cranksets

Discuss light weight issues concerning road bikes & parts.
circuithero
Posts: 6
Joined: Tue Dec 19, 2017 5:08 am

by circuithero

I'm pretty sure all of the MTB cranksets up til the new 12 speed stuff were hollow-forged. I haven't really looked too deeply into the new stuff.

robertbb
Posts: 1599
Joined: Thu Jul 23, 2009 3:35 am
Location: Melbourne, Australia

by robertbb

circuithero wrote:
Thu Mar 19, 2020 2:42 am
It's only Dura-Ace and Ultegra that are affected since they're hollow-bonded. 105 cranks and below are hollow-forged so they're fine.
Thanks... where did you see this? In fact the shimano site suggests 105 is no different from Ultegra and DA

https://bike.shimano.com/en-AU/technolo ... wtech.html

by Weenie


circuithero
Posts: 6
Joined: Tue Dec 19, 2017 5:08 am

by circuithero

I've worked in shops so I've had plenty of conversations with other industry folk. In addition to Shimano literature that the public doesn't have access to.

alanyu
Posts: 556
Joined: Thu Jun 06, 2019 1:10 pm

by alanyu

5800 is hollow forged but R7000 is bonded, while 4700 and lower are not hollow. I doubt what you have read.

robertbb
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Location: Melbourne, Australia

by robertbb


g32ecs
Posts: 707
Joined: Thu Apr 11, 2013 2:50 am

by g32ecs

I recently found an FB post on a disentegrating 6800 crank - it looks like the inner bolt is loosening up inside and the crease where the arms attach is slowly getting shredded.

I use a 6800 crank too, probably over 10,000kms now but haven't noticed anything.

ooo
Posts: 954
Joined: Sat May 21, 2016 12:59 pm

by ooo

circuithero wrote:
Thu Mar 19, 2020 3:26 am
I'm pretty sure all of the MTB cranksets up til the new 12 speed stuff were hollow-forged. I haven't really looked too deeply into the new stuff.
XTR FC-M9100 (___,175,170,165) - bonded
XTR FC-M9120 (___,175,170,165) - bonded
XTR FC-MT900 (___,175,170, ___ ) - hollow-forged
XTR FC-M9000 (___,175,170, ___ ) - left arm bonded + right arm hollow-forged
XTR FC-M9020 (180,175,170,165) - hollow-forged
SLX,XT,older XTR - hollow-forged
alanyu wrote:
Thu Mar 19, 2020 7:18 pm
5800 is hollow forged but R7000 is bonded
DA FC-R9100 (180,177,175,172,170,167,165,___) - bonded
Ult FC-R8000 ( ___ ,___,175,172,170, ___ ,165,___) - left arm hollow-forged + right arm bonded
105 FC-R7000 ( ___,___,175,172,170, ___ ,165,160) - hollow-forged
105 FC-5800 ( ___ , ___ ,175,172,170, ___ ,165,___ ) - hollow-forged
Last edited by ooo on Fri Apr 17, 2020 4:48 pm, edited 1 time in total.
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schlafen
Posts: 74
Joined: Sun Mar 24, 2019 11:51 pm

by schlafen

ooo wrote:
circuithero wrote:
Thu Mar 19, 2020 3:26 am
I'm pretty sure all of the MTB cranksets up til the new 12 speed stuff were hollow-forged. I haven't really looked too deeply into the new stuff.
XTR FC-M9100 (___,175,170,165) - bonded
XTR FC-M9120 (___,175,170,165) - bonded
XTR FC-MT900 (___,175,170, ___ ) - hollow-forged
XTR FC-M9000 (___,175,170, ___ ) - left arm bonded + right arm hollow-forged
XTR FC-M9020 (180,175,170,165) - hollow-forged
SLX,XT,older XTR - hollow-forged
alanyu wrote:
Thu Mar 19, 2020 7:18 pm
5800 is hollow forged but R7000 is bonded
DA FC-R9100 (180,177,175,172,170,167,165,___) - bonded
Ult FC-R8000 ( ___ ,___,175,172,170, ___ ,165,___) - bonded
105 FC-R7000 ( ___,___,175,172,170, ___ ,165,160) - hollow-forged
105 FC-5800 ( ___ , ___ ,175,172,170, ___ ,165,___ ) - hollow-forged
Where did you get this info?
After my own research, R7000 and up are bonded.

This guy seems to confirm it as well:

https://2lo8.wordpress.com/2018/10/12/s ... ilers/amp/

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ooo
Posts: 954
Joined: Sat May 21, 2016 12:59 pm

by ooo

schlafen, I have revisited 2lo8 info, that he posted in this thread previously:
2lo8 wrote:
Tue Apr 24, 2018 2:09 am
The bonded cranks (9000, 6800 onward) tend to be broader, more rectangular, more sylized, and slightly lighter. I'd guess due to the larger outside dimentions they are also stiffer, but I don't have issues with crank stiffness so I couldn't say. Based on these characteristics I'm guessing the inbound R7000 cranks are also bonded.
I have checked mentioned characteristics (larger outside dimentions and rectangular shape) and I have found that
while FC-R7000 are wide, they do not have rectangular shape, you can clearly see there is no glue line on FC-R7000

(and it looks like in FC-R8000 only right crank arm is hollow-bonded, left arm looks like it is hollow forged)

Image

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Greatestalltime
Posts: 113
Joined: Sun Jul 02, 2017 12:47 pm

by Greatestalltime

I had a 6700 for 35k+miles with no issues.

I got a 9000 on a new bike and replaced my 6700 with 8000 and cracked both, in the exact same spot on the right arm, in less than a year. (Around 8k miles)

Are some saying the 6700 was made better/stronger?


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RECAR77
Posts: 79
Joined: Mon Jun 10, 2019 7:12 am

by RECAR77

NickJHP wrote:
Thu Mar 19, 2020 2:56 am
circuithero wrote:
Thu Mar 19, 2020 2:42 am
It's only Dura-Ace and Ultegra that are affected since they're hollow-bonded. 105 cranks and below are hollow-forged so they're fine.
How about the MTB cranks? I have a pair of Deore XT M785 10-speed cranks. No perceptible problems with them so far, but XT is the MTB equivalent of Ultegra, so my guess would be that they're probably similar construction.
ALL previous (hollow) mtb cranks where hollow forged. FC-M9100 is the first and currently only hollow bonded crank in the mtb range

schlafen
Posts: 74
Joined: Sun Mar 24, 2019 11:51 pm

by schlafen

ooo wrote:schlafen, I have revisited 2lo8 info, that he posted in this thread previously:
2lo8 wrote:
Tue Apr 24, 2018 2:09 am
The bonded cranks (9000, 6800 onward) tend to be broader, more rectangular, more sylized, and slightly lighter. I'd guess due to the larger outside dimentions they are also stiffer, but I don't have issues with crank stiffness so I couldn't say. Based on these characteristics I'm guessing the inbound R7000 cranks are also bonded.
I have checked mentioned characteristics (larger outside dimentions and rectangular shape) and I have found that
while FC-R7000 are wide, they do not have rectangular shape, you can clearly see there is no glue line on FC-R7000

(and it looks like in FC-R8000 only right crank arm is hollow-bonded, left arm looks like it is hollow forged)

Image

Image

Image

Image

Image
Good eyes on both Image
I actually had a R8000 group last summer on one of my bikes, never noticed it, tbf I didn't know about the crank failures back then. Long gone now.

Weight difference with 50/34 rings:

5800 - R7000 = 43g meh
5800 - R8000 = 83g still meh
5800 - 9100 = 143g DANG

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pdlpsher1
Posts: 2842
Joined: Thu Jul 19, 2012 6:09 pm
Location: CO

by pdlpsher1

I ran across this site where people post pics of failed Shimano cranks.

https://www.instagram.com/thanksshimano/?hl=en

This was just posted a week ago on some great insights as to the cause of the failures.

https://www.youtube.com/watch?v=Rj__lexd_BI

robertbb
Posts: 1599
Joined: Thu Jul 23, 2009 3:35 am
Location: Melbourne, Australia

by robertbb

ooo wrote:
Fri Apr 17, 2020 4:47 pm

I have checked mentioned characteristics (larger outside dimentions and rectangular shape) and I have found that
while FC-R7000 are wide, they do not have rectangular shape, you can clearly see there is no glue line on FC-R7000

Incorrect. There is a glue line, it's just not in the same place. The R7000 drive-side arm is bonded!

Image

You can see the seam-line up the full length of the underside of the crank there. This is a freeze-frame from a "James the bike guy" video, which is here:

https://www.youtube.com/watch?v=J_zLffDJM5Y

He specifically points out that they are seamed.

(I'd also trust what 2lo8 has to say on the matter even without having seen that. That's his blog quoted earlier, and he knows his Shimano stuff!)

ooo
Posts: 954
Joined: Sat May 21, 2016 12:59 pm

by ooo

FC-R7000 spider is completely different to FC-R8000 spider, doesn't look like it is part of bonded crank arm, unless its completely different process. may be there was some side window on right arm that was glued after hollowing, but it doesn't look like 2 part

Image

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vs FC-R8000 spider:

Image
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by Weenie


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