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by Matt Wikstrom
December 2, 2016
On 31 January 2015, Richard Stanton was making his way home after an early morning ride and post-ride coffee in Canberra, Australia. He was travelling at around 35km/hr when the fork separated from his bike. A catastrophic failure of the alloy steerer resulted in profound head and neck injuries and he died three days later without regaining consciousness.
Now, a coroner’s report on Stanton’s death has determined that the failure of the fork could be attributed to fatigue of the alloy steerer and perhaps an “inclusion flaw” that arose during the manufacturing process. Both were hidden from view, occurring within the bonded assembly at the crown of the fork.
The circumstances surrounding Richard’s death seem all the more tragic since he insisted on regular services for the bike, with the most recent work completed just months before the fork failed. However, the inquest found that a thorough assessment of the fork would have been impossible without the use of sophisticated equipment (such as an X-ray machine).
The issue of component fatigue is one that many cyclists will be aware of, but I think it’s fair to say that until Stanton’s death, few have ever viewed it as life threatening. In the aftermath of Richard’s death, consumers can expect educational campaigns to raise awareness of the issue but what is achingly missing at this point is a meaningful strategy to contend with the issue of fork fatigue.
From the moment Richard Stanton started riding his bike, a Trek 2000, in 2006 he was working his way towards the moment when the fork steerer would fail. Every kilogram of load, every buzzing vibration from the road, took a cumulative toll on the alloy steerer like a nervous obsession, worrying the material into submission.
It is well known that aluminium alloy has a finite fatigue life, so the failure of Richard’s fork steerer is not unusual in that regard. I’m sure there are many cyclists that have observed or discovered cracks in an alloy set of bars, a stem, seatpost, rim or frame.
Such fatigue and failure is not unique to alloy though. Any material is subject to the wearing forces associated with cycling, and as such, every cyclist must consider that each part of the bike has a finite service life.
What is worrying though, is that there isn’t a single person, be it a mechanic, engineer or industry representative that can provide a firm figure for that service life.
That’s not to say that the industry is reckless or negligent where the durability of any fork is concerned. Indeed, this is one component that is more likely to be “over-engineered” to mitigate the risk of a catastrophic failure.
The results from fatigue testing suggest that the service life of a fork is more likely to be measured in years rather than months, however it is subject to the demands of the individual and his or her riding conditions. It is also likely to vary from one brand to another, and one level of component to another.
Moreover, while there are minimum safety standards in terms of fatigue and ultimate failure for key components like the fork, the accepted test protocols still only consider a finite amount of time, and may or may not simulate real-world use under a particular user.
Fatigue testing for forks, for example, is among the most demanding of all bicycle tests but is still only designed to simulate 12-15 years of use, according to BikeTesting.com owner Mark Rhomberg, a long-time industry veteran with extensive experience in product testing at SRAM, Schwinn, and other major brands. The fork in question here was well below that threshold, but that doesn’t account for unexpected peak loads or manufacturing defects, both of which can reduce fatigue life considerably.
“All of the numbers are taken from twenty years of testing and field studies,” he told CyclingTips. “Studies show most people hammer the bike for the first year then usage drops. The studies we ran at Schwinn showed most bikes hang in the garage and then get sold; 96% never leave the garage. For safety, ISO [International Organization for Standardization] set the bar for Europe, where usage is much higher, which is why we have adopted these standards. Peak usage is what the standards aim for, so most users are covered. Fork standards are really high, as are frame head tube tests. [The applied test] loads are ridiculous for most users.”
As good as current industry testing may already be, any test is only as good as how well it reflects reality, which is highly variable and impossible to predict with absolute certainty. In short, there is no guarantee that a component will withstand any amount of use for a defined period of time, so it is also impossible for the consumer to judge when it might be prudent to replace any given component to avoid the risk of catastrophic failure.
There are ways in which fatigue can be detected, but as mentioned above, it requires sophisticated equipment and expert personnel. Ultrasound is typically used to identify voids, de-lamination, and substructural damage in composites while X-rays and ultrasound can be used to inspect the integrity of metals.
Neither is readily available in the consumer space, so while the technology is available, it’s unlikely to serve as an effective strategy to guide mechanics and bike owners when deciding when to replace a component such as the fork.
This is a point that the coroner investigating Richard Stanton’s death was prepared to concede, hence the suggestion to raise public awareness of the issue. Nevertheless, she has called for safety standards to be revisited with the possibility of defining a safe-life limit for every fork.
Our understanding of materials and engineering has progressed to the point where it is possible to manufacture a component with a clearly defined service life, provided the stresses are well understood. This approach, referred to as safe-life design, has been embraced by the aerospace industry because safety takes precedence over concerns about cost and convenience.
Once a component approaches its safe-life limit, which is typically defined in terms of hours of use, it is replaced without pause or question. It’s an effective strategy for components that are subject to fatigue since there is no strict need for ongoing examination and assessment, yet it prevents catastrophic failure.
When the coroner investigating Richard Stanton’s death asked Trek about safe-life design within the bike industry, the company stated that previous attempts had failed due to enormity of the variables surrounding individual bike use. After all, the life of a bike can vary not only in terms of hours of use, but where and when it is used. Other variables also include the weight of the rider and their skill.
This is quite distinct from aircraft where the hours of service are carefully logged and monitored and the applied loads during use are generally very well defined.
I suspect another consideration that was left unsaid was the difficulty of convincing consumers to adhere to these recommendations. Some buyers already question the motives of the industry, so the introduction of a “best before date” for the forks (and perhaps other components) is likely to be met with a great deal of suspicion.
Nevertheless, the coroner remained committed to the idea, summing up her findings thus:
“Although nothing I can do here will bring back Mr Stanton, nor completely remove the risk of a similar catastrophic fork failure occurring in future, the actions that Trek has already committed to undertake will publicise the issues with component life and metal fatigue not only to other owners of Trek bicycles, but throughout the industry and to owners of other bicycle brands.
“It is to be hoped that increased public awareness and the prospect of international and domestic changes to relevant standards for bicycle safety will create a lasting legacy from Mr Stanton’s unfortunate death.”
Leaving aside the challenges surrounding the introduction of a safe-life limit for a moment, there are other considerations worth mentioning.
At present, the bicycle industry does not make it easy to replace a road fork at short notice. While there is a reasonable range of aftermarket products, this does not cater to all possibilities.
At the same time, a fork is typically designed in concert with the frame leading to industry-wide variations in rake, steerer, crown and axle-to-crown lengths. There is no easy way for an owner to identify every specification for a fork on a bike, yet all must be matched precisely in order for a replacement to fit and preserve the geometry of the frame.
And for those owners hoping to preserve the identity and aesthetics of their current bike, the options diminish or disappear altogether as the age of the bike increases. That’s not to say that it will be impossible to replace an aging fork, but it will be much more difficult than sourcing other components for the bike, such as a new set of wheels.
Of course, that would all change if the industry decided to support the mandatory replacement of aging forks according to a safe-life limit. I expect there would be an increase in fork production to provide a surplus of replacements and a streamlined process for ordering a replacement via local and online outlets.
I can also see an increase in aftermarket brands akin to the current state of play for replaceable derailleur hangers. While a certain amount of standardisation of fork specifications would aid this process, manufacturers need only to clearly mark all forks with the relevant information to make it easier for the consumer to identify a suitable replacement.
The risk of fork fatigue is not about to slow down to wait for the bike industry to better address the issue. While many riders will be quick to appreciate the importance of replacing an aging fork, most will be left wondering when to do it. As I’ve already mentioned above, there is no easy answer to this question.
Those riders that make a habit of replacing their bikes every few years are best placed to ignore the issue altogether. In contrast, it is almost imperative that those riding a bike that is 10 years or older should consider replacing the fork, no matter how difficult this may be.
While it seems that any fork with an alloy steerer might be the most important to replace, I don’t think any material can be exempted. This may seem alarmist, but there is no easy way to dismiss the risk of a catastrophic failure for any fork that has already endured a long service period.