Shimano Hollowtech crank failures, one year on — how the component giant's handling of this dangerous debacle is continuing to damage its reputation

It was one of the biggest stories in cycling last year. The world's largest manufacturer of bicycle components, Shimano, rolling out a recall in the United States and an 'inspection programme' in most other territories for its Hollowtech cranksets, which it finally acknowledged after years of speculation that there was an issue with.

From the 4,500 incident reports Shimano admitted it had received, to a 'Thanks Shimano' Instagram account with 18,000 followers dedicated to sharing pictures of snapped cranks, and the hundreds of emails road.cc has received sharing similar experiences and issues since the first dropped in our inbox in 2018 — the only surprise by the time Shimano finally addressed the matter last September was that it had taken so long.

This was announced in the form of a voluntary recall in North America but controversially, elsewhere, such as here in the UK and Europe, an "inspection and replacement program" was implemented rather than a full recall. 

 This meant users would take their cranks to a bike shop where a mechanic would check them using Shimano's inspection procedure and either pass or fail the component in question. 

As per the 36-page dealer's manual for the crankset inspection method, mechanics are required to undertake a process of inspecting and cleaning. Once a relevant crankset has been identified from the list below, bike shops are asked to complete an inspection with the crank arm installed, looking for "cracks or gaps" in an indicated area or listening out for "abnormal noise".

With the crankset and chainrings then removed from the bike, mechanics are asked to clean it by following multiple pages of instructions included in the manual and undertake an inspection of the removed crankset too, again looking for "issues such as cracks or gaps in the crank arm".

If found, "immediately stop use and replace the target product", the manual concludes, suggesting that if no issues are found the chainrings and crankset can be reinstalled and continue to be used. Cranksets that failed are shipped back and a replacement issued, with bike shops here in the UK receiving £35 reimbursement from Shimano for the time and work.

The view from bike shops: An efficient inspection process, but legal questions remain

The programme has raised concerns. After all, just because a crankset appears fine today, what's to say it won't have an issue in the future after more use? Some riders have reported this exact thing happening and leaving them with damage to a crank that had previously passed its inspection.

It was a point raised recently by a director at Lake District bike shop Mapdec Cycle Works. The rider snapped his crank during an interval session shortly after it was passed, when inspected immediately after the inspection programme commenced.

Mapdec owner Paul Vousden also claimed Shimano's UK distributor Madison had "banned" his shop from the inspection programme, although that outcome appeared admittedly to be in response to the bike shop owner uploading a video to YouTube in which he told viewers, "We don't bother inspecting them, we just ship them back."

> "Banned" bike shop claims Shimano won't let it inspect Hollowtech cranksets as part of "inspection and replacement" programme due to failing 100% of them

Vousden backtracked subsequently and insisted they were inspecting cranks properly and suggested he simply felt uncomfortable with Shimano's binary requirement to either pass or fail a crank, especially when he had seen evidence of cranks that passed the inspection subsequently snapping or delaminating in the near future.

"Our policy was always we don't want to be the one that says this is a pass, we always thought that, even though Shimano gave a liability release, that liability release in our mind wasn't strong enough," he explained.

 "Also we had customers coming up to us and saying: 'Well how do I know it's safe?' They'd come back a week later and say: 'Can you inspect it again it's still creaking? I'm not convinced this is not going to fail... I want a new one, I'm just going to keep coming back every week until you fail it'."

He also raised concerns about liability in a potential case where a customer, using a crankset that his bike shop had inspected and passed, suffered injury or death in an incident caused by that component failing.

"I think that solicitor would very quickly identify there are two places to source compensation, from Mapdec — we inspected it, we said it was safe and we would be the last person to have touched — and Shimano," he suggested.

"That claim would come into me, I would say: 'Hey, I've got a liability release from Shimano, this is part of a crank recall'. But even if that played out, it is still a load of time and effort and stress and I've got better things to do than fight out a case... we're busy enough as it is [...] I'm really proud of our stance, I will always put my customers first."

Thomas Jervis, a partner at Leigh Day law firm, agrees the inspection programme raises questions around liability and suggested bike shops "would potentially be front and centre answering to any legal proceedings which followed" if a customer's passed crank subsequently caused injuries or worse.

In the worst-case scenario, if a fatality occurred, he pointed out the bike shop would, at the very minimum, be part of the inquest into the rider's death, or could be sued through the courts. 

"Even if Shimano were ultimately paying the bills behind the scenes, what happens to the reputation of the bike shop in the meantime and the stress it might cause those individuals?" Jervis asked.

Whether you agree with its implementation in the first place or not, one minor plus does seem to be the inspection programme having worked fairly seamlessly for bike shops — Darren Lea-Grime of That Tiny Bike Shop in Manchester reporting "returns were dealt with in a timely way" and "we were paid pretty quickly for the work".

With that said, he would have liked to see the inspection programme advertised better as some customers were still unaware of it. Also, while delivery of replacement chainsets was "quite swift", bikes were often in the shop for longer than customers expected.

"In some cases with regular customers, we loaned them a second-hand bike," he explained. "We are a small shop but even so we have done quite a few checks. Any failed chainsets were replaced pretty quickly assuming they were in stock. The one issue we did have was a Dura-Ace chainset which was no longer made in the 53/38 ratio of the failed one, in this instance the customer accepted an alternative replacement.

"For me, the proper approach would have been to recall all the chainsets given the potential for failure and/or injury. I view it as a bad product as opposed to a bad batch."

"Can a consumer really feel confident that their affected crank is 'safe' if it passes a bike shop inspection?"

On the customer front we've heard from riders who had their cranks inspected and replaced quickly without issue, but one road.cc reader told us their trust in the component had completely gone, even if a local bike shop had passed it to continue to be used.

"The advice was just to listen out for any unusual creaking," they said. "There's nothing to see on mine — but the riders who've had their cranks fall apart probably thought that too. I've replaced it with 105 — you don't enjoy or look forward to riding the bike with the knowledge that the fault is potentially there."

Another, who shared this picture [below], was left limping 33 miles to the nearest train station, mostly on their left leg, but received a replacement crankset eight days after taking it to a bike shop, faster than the expected two weeks.

During the fallout to Shimano's announcement last September, the UK government's Office for Product Safety and Standards (OPSS) published a product safety report that concluded the affected Shimano cranksets "do not meet the requirements of the General Product Safety Regulations 2005".

To that context, Leigh Day lawyer Jervis told us "the number one priority for Shimano should be that no more riders are harmed" and the government should have stepped in and demanded that an official recall and 'stop ride' notice for the affected products was issued.

A year on, Jervis stands by the view that, in such a situation, a full recall "should always be at the forefront of any manufacturer's mind" and would have given customers more clarity.

"When the safety of a product comes into question where the consequences of it going wrong could result in death or life-changing injuries for the consumer, a full recall should always be at the forefront of any manufacturer's mind, in my view," he explained. 

"A major problem is that the public still do not know exactly how many affected products were supplied to the UK market in the first place versus how many have been 'remedied' by the inspection programme and whether that has stopped any further failures/incidents occurring.

"Is the message reaching all affected riders? Shimano should hold the keys to that data and they should consider publishing that material if they are confident it has worked. I won't be holding my breath that they will however. 

"Without that information, can a consumer really feel confident that their affected crank is 'safe' if it passes a bike shop inspection? A full recall would have provided much more clarity in that respect."

He also suggested Shimano "might want to reflect" on the minimal apologies to customers in future too, as aside from a short remark on its website stating "we apologise for any concern or inconvenience this may have caused to our consumers", Jervis points out there has been little in the way of "publicly apologising to consumers or acknowledging that they got things wrong on this occasion".

What about elsewhere in the world? 

A class action lawsuit was filed in the US against Shimano for providing "inadequate cranksets" which have put cyclists across the country at risk of injuries. The bike brands Specialized and Trek were also included, accused of describing their bikes as "perfect" and "the world's best" which was not accurate due to the "defective cranksets", alleged the 72-page lawsuit.

Elsewhere, in South Africa, there has also been a report of issues with the inspection programme, although road.cc has not been able to verify the claims with any bike shops. One rider had claimed Shimano's distributor Cool Heat was refusing to replace cranks. When we contacted Cool Heat for comment on the allegation, the distributor told us Shimano would deal with the question, the manufacturer subsequently not offering any comment on the claim when asked.

Since the initial announcement, the brand has revealed the cost of the crank inspection programme, its financial report for 2023 stating it lost £93m in sales as a result and the "extraordinary losses" cost the company around 2,762 million Japanese yen (£14.5m). In the same year, Shimano posted a £322 million profit and a figure for how much the crank inspection programme cost the business this year has not yet been provided, but will presumably appear when the company releases its financial results in early 2025.

What is actually wrong with the products?

When we investigated the issue last year and sent some cranksets off to a lab to find out what an expert had to say, Dr Mark Bingley — a mechanical engineer at the University of Greenwich — concluded that the initial stage of the failure process involves partial failure of the adhesive bond between the inner and outer U-shaped channels that together make up the rectangular tube section of the crank arm.

Despite corrosion being a known factor that can weaken adhesive bonds, there was no evidence of corrosion found on the examined parts. He was unable to ascertain a reason for the debonding between the channels initiated, even having considered possibilities including: flaws resulting from the manufacturing process, environmental deterioration and fatigue.

"Any proposed solution to the problem will depend on how frequently failures occur," he suggested. "If rarely, then this might be considered acceptable by the manufacturer. If it is a frequent problem the recall of the product and a redesign will be necessary. The simplest and cheapest solution would be to reinforce the adhesive bonds with mechanical fixings. However, this might not be considered acceptable for aesthetic reasons."

How the failure manifests itself on the road can vary, although our email and social media inboxes having received so many accounts gives us a decent view of some recurring points. 

 Debonding often occurs on the driveside, where there is cracking on the arms of the spider, and then the crank arm fully detaches as the outer shell comes away. Another common fault location is cracking on the inside of the driveside crank arm. Non-driveside crankarm failures have also been reported, but there are far fewer documented to our knowledge.

From the testimony we've received from readers, there aren't always warning signs as to when a crankset is going to fail, but we do know that issues appear to start out as a creaking that riders aren't able to get to the bottom of. Other telltale signs can be pedals feeling like they are misaligned or bent.

There also doesn't seem to be a particular pattern as to how far one must ride before a failure occurs, but the failures are always on well-used cranksets. This could explain why the issue has never arisen in the top levels of professional cycling, where equipment will be new or nearly new, more often than not. 

Online forums where mechanics have discussed their experiences during the past year suggest that, anecdotally, bike shops are failing more cranks in wetter climates compared with counterparts in hotter, drier parts of the world. Of course, without any data on this, the point remains purely anecdotal. When we asked Shimano if it had any numbers or information about this, no specifics were disclosed.

Ultimately, whatever the reason for the failures, Shimano's handling of the situation has impressed few. From customers, to bike shops, mechanics, other industry figures and legal professionals, we've heard, more often than not (and by a fairly large majority too), that people feel the lack of recall and instead opting for an inspection programme was an unsatisfactory response. In fact, we'd go as far as to say the response has been unsatisfactory to everyone other than the brand itself.

Even in the best case scenario of someone having their crank replaced quickly and efficiently and a bike shop receiving timely reimbursement for the work, it has left a bad taste in the mouths of many.

'How do we know our cranks aren't just going to snap next week, month or year?', 'How can we feel safe and confident using it in the meantime?', 'Why was I even riding it in the first place?' Those are questions we've heard plenty of times in the past 14 months.

They are questions we put to Shimano too, among other queries about many of the issues raised in this piece, however the components giant declined to comment.

Editor's note: A special thanks to Leigh Day Solicitors, bike shop representatives and road.cc readers who contributed to this article. 

It's been well over a year since Shimano acknowledged an issue with its Hollowtech cranksets, and we still get messages in our inbox from victims who have experienced catastrophic failures while on a bike ride — bike rides that the vast majority of us do for enjoyment, and to get away from the stresses of everyday life. Thankfully we've had very few injuries reported to us, but while hundreds of thousands of these products are still out there, we dread getting an email reporting something much more serious. 

There are already enough dangers on the road that, in rare circumstances, have the potential to take away from this enjoyment. There is no good reason why the world's biggest manufacturer of bike components are continuing to add another one through its disappointing handling of this situation. Full recalls on this scale have been done before, and from what we've seen so far, there appears to be no practical or financial benefit to the 'inspection and replacement programme' vs simply replacing all sets of Hollowtech cranksets, no questions asked. 

Almost all of us at road.cc continue to use Shimano products, and the brand rightly receives regular praise for the reliability and effectiveness of its current product line-up in our coverage. This makes it all the more disappointing that a company we otherwise respect and trust is continuing to let its customers down. 

While road.cc, other media outlets, members of the public and legal professionals have worked to spread awareness, only a proper worldwide product recall will ensure that as many of the customers affected as possible will have their potentially defective Hollowtech cranksets replaced.