Shimano denies design problem with Hollowtech cranks despite reports of cracked arms

So let me get this straight; Shimano are saying that just because yours failed, there is actually nothing wrong with it because others didn't. Genius!

70kg here! Must be a low weight limit!

it wouldnt be the riders weight per se,  it would be the torque forces or the twisting force being applied by the rider on the pedal to get the bike moving,and the metal is just suffering from fatigue cracks which grow over time till the component fails completely.

This, and I'd add is this really where you want to be testing the design limits? I have older Dura-Ace 7600's, 177.5 which I think are solid. But they're on a 2015 Trek Domane that originally came with 6800's (I needed the length, not available in 6800s). They're going into the box with the custom steel fork rusting out around the crown.

I like Shimano too, but not their cranks. That's why my builds all have Rotor cranks. Think their old 5 arm design with NoQ rings look classy too.

nopants wrote:

My Ultegra 6800 cranks failed recently as well. The 2 halves of the arm came unstuck at the axle end. It had been creaking for a while, and luckily I was able to get home before it failed completely.
It did have a lot of miles on the clock. Worth checking if you have an old ultegra/dura ace crankset. In my case I could see (and feel) the outer shell flexing away from the chainrings when I weighted the pedal. The inner shell of the arm is cracked down by the pedal.
Almost impossible to find spares at the moment too...

I had the same problem, it looked exactly like yours. I was about 6 months outside the warranty but persued it with the UK distributor rather than Shimano, and got a replacement. Ultegra 6800. I also knew there was something wrong but couldn't find it, until it got to the stage where it was flexing as I pedalled. I was on my way to Rosedale Chimney, luckily I spotted it before the climb 🙄😉 I still had about 25 miles to roll home gently though, expecting it to let go any minute.

Probikekit have 105 chainsets at £116. Different construction and should work nicely.

Thanks for that. I have 6800 groupset and had experienced squeaking, have oiled and changed everything except the flipping cranks - though i did check the bolts. Will have ot check it's integrity. Still have old 105 crankset kicking around so will swap out check to see if the creak/squeak has gone.

Also a lot of Ultegra r8000. Actually didn't see it with models before r8000 yet, but it might be from the moment the hollow tech technique was introduced.

Dura Ace R9150 crank weight 614g, SRAM Red AXS crank weight 561g, so bang goes that argument.  

As for recycling? Bearing in mind the heavy steel axle through the middle plus steel inserts for pedal attachment, how much of that 561g of the SRAM crank do you suppose is carbon fibre, compared to the weight of Lycra (non recyclable) the average cyclist goes through during the life of a carbon crank? Back to merino wool it is then! 

No, I'm not being flippant. In the UK, household waste amounts to 400kg per person per year, of which only 44% gets recycled. If you really want to reduce landfill, say 100g of carbon crank per cyclist every 10 years (10g per cyclist per year) is hardly the place to start.

Reduce, Reuse, Recycle in that order.   Needing to buy replacement cranks is hardly reducing comsumption.

rct wrote:

Reduce, Reuse, Recycle in that order.   Needing to buy replacement cranks is hardly reducing comsumption.

Absolutely, and I would expect cranks to last pretty much the life of a bike. My Ultegra crank failed after 5 years.

"Dura Ace R9150 crank weight 614g, SRAM Red AXS crank weight 561g"

Theres still lighter and better : https://www.renehersecycles.com/shop/components/cranks/rh-11-speed-doubl...

Reneherse is only lighter without the shaft (in the bottom bracket), no?

Is kudos really an appropriate response to a product that endangers users like this?? You should perhaps ask instead why such fragile thin-walled aluminium is still being used in a premium groupset (9100 and 9200).

Flagship bike products (framesets, groupsets, wheelsets) are carbon for good reason. Carbon is stiffer, lighter, and stronger than alloy. Your frame and wheels are probably carbon.

The failure modes on the insta page are all the same, not random, showing a common design fault in a thin-walled aluminium design pushed just too far in its struggle to match the low weight of carbon.

With the new 9200 DA shimano have finally given-up pretending aluminium painted black is even comparable with carbon, making the c/set heavier (690g vs 624g before) due to 9100 breakages. Zero surprise, the campag SR carbon c/set is 11% lighter and 6% stiffer.

Using relatively low-cost aluminium and some black paint for manufacture may generate great DA profits for shimano, but it’s hardly the pursuit of marginal gains (and safety) expected in a flagship groupset.

HiFi wrote:

.

Flagship bike products (framesets, groupsets, wheelsets) are carbon for good reason. Carbon is stiffer, lighter, and stronger than alloy. Your frame and wheels are probably carbon.

I snapped a pair of Specialized s-works carbon cranks so I'm not sure it's all down to material choice.

anke wrote:

Nevertheless: Cudos to Shimano for their elegant and cost-effective designs!

Is this a joke, I can't tell if you're trying to be funny or not. I hope you are. 

Look, the design for manufacture, mass-production, weight, and affordability, based on cheap materials, as mastered by Shimano, is most impressive. -- Just producing an expensive clunk from the most expensive material available is child's play compared to this (but can be done by smaller companies without the production and engineering resources, if these companies can demand high prices).

But as I wrote before, I totally agree that Shimano did not seem to handle this problem (cracked crank arms) in a graceful way. 

anke wrote:

Look, the design for manufacture, mass-production, weight, and affordability, based on cheap materials, as mastered by Shimano, is most impressive. -- Just producing an expensive clunk from the most expensive material available is child's play compared to this (but can be done by smaller companies without the production and engineering resources, if these companies can demand high prices).

This post has no more fact than your previous post. Shimano have "mastered" nothing here, the cranks break, people get hurt, have you not been listening? As for the nonsense about affordability and cheap materials versus "the most expensive material available" if you had actually checked you would find that  SRAM Red 22 (carbon) are cheaper (by msrp) than Dura Ace R9100. The company "demanding high prices" as you put it, is the one using cheap pieces of cast aluminium badly glued together.

I think you're exagerating a little, my dear Griff500. It also seems you didn't read my post properly, did you?

anke wrote:

I think you're exagerating a little, my dear Griff500. It also seems you didn't read my post properly, did you?

In defence of Shimano you have so far said they are light as the opposition, (they aren't in all cases eg DA versus Red), lauded them for use of cheap material, despite the end product in some cases being more expensive (eg Dura Ace versus Red), and described them as masters of DfM, despite a clear pattern defect in use. Now which bit do you think I got wrong?

Right. So Mr ex black belt would design bike-parts to a six sigma level of reliability, so there might be just shy of 4 failures in one million parts, over many, many years, in possible highly corrosive environments? What's the weight penaltiy? Pro-level bicycle parts (or at least very high-level ones) - not the stuff for the daily commute?!