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TECH NEWS
hawinspeter crank arm failureShimano denies design problem with Hollowtech cranks despite reports of cracked arms
Shimano says that there isn't a design problem with its Hollowtech cranks despite reports of a pattern of failures – although its engineers are continuing to investigate other factors or causes.
The hollow design of Shimano’s Hollowtech crank arms makes them light; decreasing the rotating mass helps with acceleration. A lot is to be gained and Shimano says on its website, “The challenge is to reduce the weight of the crank without reducing its strength and rigidity.”
So, is the balance right?
road.cc reader hawkinspeter shared with us all in a forum post last month the result of an uninvestigated creaking noise. The photo shows the Hollowtech crank arm cracked completely and split in two. This failure resulted in the rider hitting the deck.
He explained that the noise repeatedly occurred when accelerating from a standstill, but that he was unable to get to the bottom of the issue until the crash when it became clear Shimano’s Hollowtech crank arms had been the source.
This is one reader’s incident, but there are more. When we shared the photo on our Instagram page we got countless replies detailing similar incidents, so much that it spawned a whole road.cc Podcast episode on scary cycling incidents. An Instagram account with 11.1k followers, @thanksshimano, shares photos documenting similar issues, with new posts every day or so.
@thanksshimano reckons the issue is that “none have properly treated internal surfaces and all rely on 'perfect' bonding which we know to be sometimes imperfect”.
It’s clear hawkinspeter’s failure isn’t a one-off, but we have no way of putting a definitive figure on it.
Shimano sells a vast number of these cranks – there are far more out there than cranks of a similar level from SRAM or Campagnolo, for example – so it’s almost inevitable that there will be more reported failures. It would be interesting to see the number of incidents versus the number sold, but we have no way of getting these figures. Nor can we tell you about the history of any particular product that has failed.
What we do have, though, is a response from Shimano on the issue.
We brought the reported failures of cranks to the company’s attention and in a nutshell, Shimano says there is no design problem, but that it is still looking to find out if there is a specific cause.
Here’s the full response we received:
“Thank you for bringing the reported failures of cranks to our attention. We take customer complaints seriously and, as a result, we initiated an investigation.
“Crank failures do occur, even though our cranks do not have any design problems or if there are no other easily identifiable issues.
“During our examination of usage cases, and through our own internal testing, we have not identified a design problem with the cranks, and we are continuing our investigation to discover other factors or causes.
“We would like to be able to give further details, but we cannot at this point because our investigation has not resulted in the identification of a cause of the crank failures your readers reported.
“We would like you to know that your readers' complaints are not being ignored, and Shimano's engineers are trying to find out if there is a specific cause.”
Have you had a Shimano crank fail? Please get in touch and tell us what happened.
Anna has been hooked on bikes ever since her youthful beginnings at Hillingdon Cycle Circuit. As an avid road and track racer, she reached the heady heights of a ProCyclingStats profile before leaving for university. Having now completed an MA in Multimedia Journalism, she’s hoping to add some (more successful) results. Although her greatest wish is for the broader acceptance of wearing funky cycling socks over the top of leg warmers.
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124 comments
The non drive side is hollow, but does not appear to use the bonded structure of the drive side. I just sectioned mine, and no sign of a bond line. Looks to me like a single piece casting or extrusion, though I'm no expert. This is very different to the drive side, which has overlapping lips which act as the bond surfaces, rather like an airfix model.
Well, that definitely looks like it's hollow-forged. That raises the question of why they used different techniques for the left and right sides.
Because one is attached to a ring, and the other is only attached via a bolt?
Even for the non-drive side, the hollow-forging is quite an achievement. Doing this on the drive side, and with hollow crank-arms, seems almost impossible...
Well, they find it easy enough on their 105 series which doesn't suffer from the issues that the hollow-bonded Ultegra and Dura-Ace have.
They don't. With 105, the crank arm is hollow - but not the small arms connecting to the chain-ring. Making the 105 less stiff and/or more heavy, compared to Ultegra / DA. (Whereas the non-drive-side crank arms are the same between Ultegra and 105, possibly DA too.)
But then, 105 has always been a reliable "workhorse", probably better suited for sporty commuters, winter cycling or just long term use than the lighter Ultegra / DA.
Yes, that's what I would expect, I wonder about making both cranks the same, and only attaching the chainrings to the axle directly. probably make the driv side crank heavier, taking it all the way to the axle, instead of bonding (unrelaibly) to the chainrings.
I think it depends on the model, doesn't it? Pretty sure my DA 9000 left crank is also two-part bonded but would have to have a close look to be sure.
I got a new 9100 Dura ace group set in 2016. Within three months I broke the drive side cranks catastrophically as depicted in so many of these posts. It unequivocally has nothing to do with the soap you are using to wash the bike. There is a structural flaw to some of these sets. Not being a metallurgist or engineer I won't guess what but something is so wrong.
Luckily I did not crash as I eventually pulled over and inspected it , at first thinking the loud screeching- creaking noise was coming from the pedal.
With all of Shimano's talent, resources, and technical expertise, one would think they could get this right.
So mine is only six months old. I've sent these pictures to Dolan, who say there's nothing wrong even though the joints were perfectly aligned a few weeks ago and now they're very clearly not.
My tweet to @ShimanoROAD is unanswered.
And I don't know if I want to ride my bike any more.
What am I supposed to do now?
Get that replaced under warranty.
As well as checking for cracks, any non-alignment with the chainwheel (as in your photo) indicates broken bonding and it won't be safe to use.
Consumer rights act applies if bought in heh UK. The goods aren't fit for purpose so either Dolan replaces them or they refuse in which case you buy a suitable alternative and take them to the small claims court.
judging fromt he reports I would expect that to fail. I would try again with the retailer, because even if it hasn't broken, it clearly has deformed and is not as sold.
I would point out to Dolan, that this looks like te begining of a known common failure, which has the potential to cause injury, and that by denying they are potentially liable for any injuries sustained.
Does the chainset creak in use?
So they're not only ugly as hell, they're also shite...
OEMs tell shimano keep it light, keep it cheap, and this is what you get.
Shame on shimano, putting riders at risk like this.
Don't tolerate it; switch to stronger/lighter/stiffer carbon. Campagnolo carbon is highly reliable in rim/disk and mech/elec. 12x chorus £1160, SR £2160 (eg wiggle).
Exact same issue for me, though thankfully I checked out the creaking noise before it caused an accident. Shimano wouldn't cover it under any sort of warranty/guarantee though, so the replacement came out of my own pocket
I'm amazed they can claim that isn't a warranty replacement job, over two years old?
How many of these will have been washed with non ph neutral cleaner? If you want to avoid corrosion and early failure of alloy and steel components on your bike, specifically spoke nipples, cranks, bearings etc then make sure the wash is 'PH Neutral' . Fancy spray cleaners, foaming degreasers and fairy liquid in a bucket tend to be non ph neutral - choose the products you use to clean your bikes with care!
I wouldn't expect bike parts to be especially sensitive to non ph neutral cleaners considering that they should be designed to cope with the general muck that gets thrown up from the road including winter salt. Cosmetic, surface damage would be fine and expected after a few years, but not catastrophic failure.
The Shimano instructions didn't contain a specific warning about cleaning that I saw, though it did warn about checking for any signs of cracks before each ride.
Mine lasted about 25,000km including winter riding in the UK and it's been cleaned with a variety of cleaners, though mostly car shampoo. I think it's a design fault rather than which cleaner you use. You'd also expect other components to start having problems before a crank - bearings and spokes/nipples typically get a rough time from any dirt and/or aggressive cleaners.
Well you should expect it, the bikes are getting a double and even triple whammy from salt of the road in winter, salt from sweat when the bike is used on an indoor turbo trainer as well as most car washes and fairy liquid in a bucket, not to mention fancy coloured spray cleaning liquids (most of which are not ph neutral and actually have corrosives in)will instigate corrosion that will ultimately lead to failure. It is just a question of when. And for those living near and riding on coastal roads it can be a quadruple whammy if all those factors apply. Anybody who has an old hack on a turbo will know what sweat alone can do to their handlebar stem for instance. All it needs is for corrosion to be instigated, from that point forward it is just a matter of time. Granted the cranks appear to be bonded, which is a weak point any corrosives will expose, and they I think will need to redesign them. But as for the weakness starting, no doubt in my mind it's winter riding, non-ph neutral wash and for those turbo bikes and ones ridden on coast they are at high risk of failures on all alloy parts in the long term, Shorter if a combination of these things apply.
I think you're missing hp's point - given that all that is going to be thrown at it, they should be designed to withstand it. Otherwise they're not fit for purpose.
I don't doubt that corrosion happens, but that doesn't look to be the issue with the problem cranks. Looking at pictures of them (and my own example), there's not clearly signs of corrosion. Also, why would 105 cranks be not susceptible to the same corrosion?
No - it's a manufacturing/design fault with the hollow-bonding in my opinion. When my crank snaps again, I'll go for 105 to replace it.
Here's mine : 6800, in 2018. I am certainly no powerhouse, but this happened (just) inside the warranty. Planet-X did replace it under warranty, with an r8000, which I sold.
I totally distrust this design, and will never use this "hollowbond" type again. I will stick to 105/R7000, which use a different manufacturing technique - basically a forged hollow tube closed off at the pedal end.
I think, as others have said, any imperfection in the bonding allows moisture (and salt in our UK climate) in to cause havoc. Once the bond is weakened, the whole thing is inherently too weak and WILL fail.
I've had it happen to 3 ultegra cranksets over 3 years with two different bikes. All Ultegra 6800 (52x36 crankset on a road bike, and 46x36 CX style crankset on a CX bike). On one bike, the warranty replacement failed with 1 year after covering only about 2000 miles.
Only one of those was covered under 2yr warranty, the others were refused as out of warranty period ... so 105 was used to replace them, as that doesn't have the cranks manufacturered as two separate pieces and bonded together.
Some reports online suggest it's to do with salt water due to coastal riding (uk) and winter riding (uk) and that it's somehow getting into the void of the crankset and causing a corrosion like reaction with the back face of the crank arm while ultimately weakens the bonding agent for the two parts. Starts off with a minor amount of play which due to constant flexing from the pedalling motion builds into a fatigue crack forming and ultimately full crank failure as it shears off. Usually get a bit of warning with a bit of creaking, or if your frame tolerances are tight (as in my case) then the crank arm will flex enough to hit the chainstay (!!!).
These failures happened about 4 years ago and it was a known problem then, but Shimano were failing to acknlowledge there was a problem and buried it. It also happens to Dura-Ace of the same time period as 6800, and I believe R8000 etc are also affected due to a similar two-piece bonded design.
I have had an Ultegra 6800 failure, I am not a UK rider, l live in the South of France, 50 miles inland (no salt, even on winter roads), I rarely ride in the rain, and although we get winter temperatures down to zero, that is hardly extreme.
What would really help is an in-depth look by Road CC at the new 12-speed versions of Dura Ace and Ultegra to see if the issues could persist - perhaps talk to some materials experts about why the failures are happening now and whether Shimano has addressed them (it appears the new cranksets are heavier so that may be a pointer)?
"Secret_squirrel wrote: I don't blame Shimy with sticking with what works."
Feeling a bit sheepish this morning?
Curious as to where the 'cut-off' is for failure prone vs. not.
I've got some 7000km old Ultegra (6800 I guess, 4 arm) with Absolute black chainrings on them. I'm approx 3W/kg on a good day.
Bike sees virtually no rain though, is on turbo duties 6 months of the year and sunny rides only the rest of the time.
Maybe this is the justification I need to buy those Cane Creek ee-Wings in my local shop window. Big welded titanium tubes, what could possibly go wrong!
At least 6 Ultegra 6800 cranks have failed this way in our club ... I would suggest failure of these cranks is an inevitably. I have a spare set from a written-off bike and am waiting for that tell-tale creak to start... Looking at Rotor as replacement.
6800 failed in Spring this year on my 2017 Defy.
Good mileage but I am neither heavy (78kg) nor strong (15mph averages on 65ish mile rides in Warwickshire, no not many severe hills). I also tend to spin rather than grind up hills - what sane cyclist would stand when they can laze around on a seat?
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