Support road.cc

Like this site? Help us to make it better.

TECH NEWS

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

Component giant says its engineers are trying to find out if there is a specific cause of crank failures

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?

Image from Shimano's website Tech_Image_HollowtechCrankArm_01

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.

hawinspeter crank arm failure

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.

Add new comment

124 comments

Avatar
HiFi | 2 years ago
2 likes

Solution to these problems. Superbly engineered carbon 12x chorus groupset £1160, SR £2160 (eg chain reaction).

Avatar
Pacemaker | 2 years ago
1 like

My Ultegra R8000 crank went on my 2017 Canyon Endurace CF SL, it was replaced by Shimano (through Madison their distributor) after I complained to Shimano, this was despite the bike being 4 years old. It had been well cared for and serviced by my LBS. I thought that the pedal had gone as it felt like it had broken and the pedal was moving and slightly oblong shaped feeling as I pedalled, at first couldn't see anything but whilst climbing a fairly sharp but short hill looked down and saw that the crank was split and coming away from the arm. It has left my slightly apprehensive about this type of design as a result of this failure.

Avatar
Chicken legs 7 | 2 years ago
1 like

I have 2 cranksets break in this manner. Both 6800 ultegra.

Avatar
Roger Patterson | 2 years ago
1 like

I had 8000 ultegra cranks, then about two months ago I felt this flex on the drive side. I thought it was my cleats, but after about 2 more rides i took the bike in to my LBS and sure enough there was a crack in the arm about 5 cm long. I contacted the LBS i ordered them from and Shimano warrantied the cranks. They were about 1.5 years old. Now i just have to wait for the news ones which also may crack.

 

Avatar
Jem PT | 2 years ago
2 likes

This happened to a guy in our club this week.

Avatar
wtjs | 2 years ago
6 likes

Shimano's engineers are trying to find out if there is a specific cause

There is! It's people pushing too hard on the pedals. I'm pleased to announce that as a result of delicate pushing I have never broken a crank- on the other hand, I only have the boring old non-glued Hollowtech or ordinary alloy spider types

Avatar
postrestant | 2 years ago
0 likes

Peak Torque has a vlog on this

Avatar
Rozzy | 2 years ago
3 likes

It happened to me today on my gravel. 1,5 years old 8000. Disappointed..

Avatar
Sniffer | 2 years ago
1 like

I am the latest to suffer this failure.  An Ultegra R8000 crankset.

New creak last week when I was out of the saddle.  Felt the drive side pedal leaning away from the bike, but wasn't sure if this was real or not. 

Small, but definite crack.  Bit relieved that I didn't ride it to failure.

Bike bought in 2018 and only covered 3,350 miles on it. 

A bit unimpressed.  I have already replaced the brake calipers that were leaking fluid last year.  These failures shouldn't really happen.

Avatar
alanmy | 2 years ago
1 like

Yes this week had same problem. Feel like it must be design and or manufacturing problem. 10000 miles 4 years old is surely not a reasonable lifetime for a premium product

Avatar
MrStubblefield | 1 year ago
1 like

I know this thread is a bit old, buy my Ultegra 6800 failed about two weeks ago.  I was going up a hill at the time, but fortunately I was in the saddle and managed to stay upright. 

Unfortunately, I'm having serious difficulties getting in touch with Shimano for some sort of remedy.  Canyon has not been great at helping me out in this matter, but perhaps that's what I get for not buying a bike at my LBS.

My bike is just over four years old - so outside of the parts warranty - and I'm rather put out at the thought of having to purchase a new crankset for a bike that I'm probably only going to use for another year or two.

 

Avatar
Dingaling replied to HiFi | 2 years ago
3 likes

I'll endorse that. I've had campag record on my road bikes for the last 22 years and never had a problem. I've been using SR EPS since 2016 and wouldn't dream of using anything else.

Avatar
hawkinspeter replied to Sniffer | 2 years ago
1 like
Sniffer wrote:

I am the latest to suffer this failure.  An Ultegra R8000 crankset.

New creak last week when I was out of the saddle.  Felt the drive side pedal leaning away from the bike, but wasn't sure if this was real or not. 

Small, but definite crack.  Bit relieved that I didn't ride it to failure.

Bike bought in 2018 and only covered 3,350 miles on it. 

A bit unimpressed.  I have already replaced the brake calipers that were leaking fluid last year.  These failures shouldn't really happen.

Glad to hear you didn't experience it failing, but a failure after 3,350 miles is unlucky.

Avatar
Simon E replied to HiFi | 2 years ago
2 likes

I'd love to try a Campagnolo groupset, to see whether there is any real difference. But £1160 is £400 more than I've ever paid for a complete bike!

My (much cheaper) solution would be a 105 groupset. Good enough for everyone, even for racing. Unlike Ultecrack and Dura-break, the crankarms aren't stuck together with Airfix glue.

Avatar
SimoninSpalding replied to Simon E | 2 years ago
2 likes

Of course you don't need the whole groupset. I successfully ran a Campag Ultra Torque crank with Shimano for a while until I got the other bits to go fully Italian. You will need new BB but other than that they are interchangeable.

I would recommend avoiding the Power Torque chainsets but any model of Ultra Torque, alloy or carbon seem bullet proof.

Avatar
hawkinspeter replied to SimoninSpalding | 2 years ago
1 like
SimoninSpalding wrote:

Of course you don't need the whole groupset. I successfully ran a Campag Ultra Torque crank with Shimano for a while until I got the other bits to go fully Italian. You will need new BB but other than that they are interchangeable.

I would recommend avoiding the Power Torque chainsets but any model of Ultra Torque, alloy or carbon seem bullet proof.

Mixing Shimano and Campag?

Avatar
Hirsute | 2 years ago
1 like

I've had 2 goes this week at sorting out a creak. I hope it was from not getting the cassette tight enough (isn't it in the region of 50 Nm?) rather than the first signs of danger from a 6800.

Avatar
Sriracha replied to Hirsute | 2 years ago
2 likes

I had a creak, more of a click really, on the left pedal stroke. I suspected the pedal, bearings were stiff that side, but the click remained with new pedals. The click was progressively getting more noticeable. So I took it to LBS to check out the BB. Nothing.

As I was putting it in the car I saw it - cracked seat stay (alloy frame) on the other side. Bugger.

Avatar
wtjs replied to Sriracha | 2 years ago
1 like

cracked seat stay (alloy frame) on the other side

I had a noise which I took too long to identify because it was a crack in the mid seat-tube on a reputable steel frame. You don't expect it! It was sorted out by the shop and is fine 10 years later

Avatar
Dingaling replied to Hirsute | 2 years ago
2 likes

The ultegra cassette lockring that I took off and cleaned yesterday says 40nm.

Avatar
theflatboy | 2 years ago
1 like

I sold a set of R9000 Dura Ace cranks on, the guy who bought them told me a few months later that they'd failed in that way and he'd had quite a bad accident as a result. Then about six months later the same thing happened to mine - three year old R6800 cranks, realised gradually over a couple of hundred miles what the weird feeling was in the pedal stroke, by the time I realised what it was they were coming apart quite badly. Supposedly they're being replaced under warranty, but that's been over a year now and nothing back to replace them yet (the shop handling it for me is doing me a favour as they were originally bought from a different shop as OEM, and that shop no longer exists)...!

Avatar
theflatboy replied to theflatboy | 2 years ago
1 like

Oh yeah, and looking at Hope or Rotor to replace the Shimanos on both my road bikes at the mo to avoid likelihood of it happening again...

Avatar
wycombewheeler | 2 years ago
2 likes

I've done nearly 12,000km on my Vaaru with ultegra cranks. Just over two years old.

maybe full length mudguards helped, maybe I've just been lucky. I will pay more attention to any creaking noises and inspect the chainset for any sign of misalignment.

Avatar
wtjs | 2 years ago
1 like

This topic has certainly worked on me! I'm an (almost) lifelong Shimano devotee, and I don't think I've ever had a Shimano component fail unreasonably, but I wouldn't buy one of these 'bonded' efforts.

Avatar
Cps1001 | 2 years ago
2 likes

Whether they admit it or not this looks/feels like a design fault.  Mine failed after around 5000 miles and that was without huge amounts of wet weather or high humidity.  Fortunately I found out what the "clicking" was before it actually snapped and could cause a crash - but not until I swapped out pedals, repalced the BB, changed my cleats.  Did not expect a crank failure but afterwards found some comments on forums showing that this is not an uncommon occurance.  Seems like the QA or the bonding is better on DA.  Meanwhile my 6700 crank is still going strong!

Avatar
Bubba Tex | 2 years ago
2 likes

I setup an account here just to post to this. I am on my 4th R8000 crank since April, 2018 - 2 have been warranty replaced but I bought the 4th because I needed a quick replacement (and I have a spare now). All of mine have cracked on the drive side arm joining seam to the left (when looking at the bike as the picture above). This would be the seam that catches most of the sweat as well as all of the pdeal stroke power. Shimano did ask me if I lived in Flordia or on the coast (I don't) on my last warranty exchange - so salt related erosion is a concern of theirs (and I sweat ALOT). Until they make a change to this design, I am not buying Shimano any longer (35+ year customer) - or at least not the crank.

Avatar
anke replied to Bubba Tex | 2 years ago
0 likes

This is an "impressive" experience (glad you're fine!). May I ask if there is anything special about yourself, your environment or your riding style? (Strong sprinter, overweight, using Ultegra for Gravel, extra-long pedal shafts...?)

Avatar
wycombewheeler replied to Bubba Tex | 2 years ago
2 likes
Bubba Tex wrote:

I setup an account here just to post to this. I am on my 4th R8000 crank since April, 2018 - 2 have been warranty replaced but I bought the 4th because I needed a quick replacement (and I have a spare now). All of mine have cracked on the drive side arm joining seam to the left (when looking at the bike as the picture above). This would be the seam that catches most of the sweat as well as all of the pdeal stroke power. Shimano did ask me if I lived in Flordia or on the coast (I don't) on my last warranty exchange - so salt related erosion is a concern of theirs. Until they make a change to this design, I am not buying Shimano any longer (35+ year customer) - or at least not the crank.

I can't see how the drive side crank would be subjected to more sweat or greater forces than the non drive side crank.

It does seem strange that the drive side is normally the one that fails, but I would suspect a difference in fabrication.

Avatar
anke replied to wycombewheeler | 2 years ago
0 likes

The drive-side is very complex and glued together, the non-drive side is (I'm fairly sure) a single piece...

Avatar
hawkinspeter replied to anke | 2 years ago
1 like
anke wrote:

The drive-side is very complex and glued together, the non-drive side is (I'm fairly sure) a single piece...

I think both cranks are hollow bonded, but drive side is a more complex shape.

Pages

Latest Comments