On my post about the 2011 Jamis Coda Sport, a reader left an interesting comment about the catastrophic failure of carbon forks. When I was writing the post, it never occurred to me that the carbon fork, which I wanted, would be a problem for someone else.
Not long ago, I was shopping for a carbon fork for a road bike. I did a lot of research, not only on various brands, but on the safety and durability of carbon. Afterward, I felt confident enough in carbon (as a material) to purchase a carbon fork. I’m not a weight weenie. I just love a carbon fork’s ride.
I learned some interesting things. For instance, most of the “unexplained catastrophic carbon fork failure” reports are located on personal websites or in bike forums. There aren’t well-known consumer or professional cycling websites warning consumers about the “dangers” of carbon forks.
Any fork failure can cause serious injuries. Forks made out of every material have failed without warning. If steel or aluminum always gave warning, no one would have their fork fail while riding. I can’t see how a crash from one type of failed fork would necessarily cause more injury than another. Just like carbon, a failed steel or aluminum fork would cause a loss of control. The terrain and bike’s speed would have as much effect on the severity of a cyclist’s injuries as the failed fork.
Fifteen years ago, dire warnings were made about aluminum forks. In spite of those warnings, the aluminum fork failure rate isn’t significantly worse than any other fork material.
One of my bikes has an aluminum fork. When I bought it I was told that it was more likely to crack and fail than carbon or steel. For financial reasons, I settled for the aluminum fork. Tens of thousands of miles later, the recently inspected fork shows no sign of wear.
For comparison, here’s a report of an unexpected steel fork failure:
“So, I’ve been noticing that the front brakes of my road bike were acting “grabby” in that the front would shimmy pretty badly just as I’m coming to a stop. The rims felt a little sticky, maybe some Gatorade got on them and it hasn’t really rained in a while. I cleaned the wheels last night and rode into work today. It was still bad, but didn’t seem as bad. This has been going on for a week, I didn’t think anything of it. I decided to not ride after work and just come home, coming down the driveway, the grabby-ness was really pronounced, so I figure that the brake pads must be contaminated with something.
When I took the wheel off, my heart skipped a beat. Without much effort, this is the result:It was hanging by no more than 2mm of steeel. I shudder when I think of the roads I was about to go on, including one really bad bump at the bottom. I don’t think it would have held together and when you lose the front like this, it’s going to be bad.
The shimmy was the wheel moving back and forth due to the fork leg being fatigued. There hasn’t been any accident damage since I put this fork on the bike. The crack was almost all the way through, starting from the BACK of the fork leg.”
This cyclist had no reason to suspect that the bike’s behavior had anything to do with the fork. The same thing could have happened to anyone. There are as many misconceptions about steel and aluminum as there are about carbon.
VeloNews technical writer Lennard Zinn, a frame builder, former U.S. national team rider, and author of several books including two successful maintenance guides wrote an article entitled: Technical FAQ with Lennard Zinn: Carbon Forks.
Here, Zinn and manufacturers answer questions about rider weight limits, the lifespan of carbon forks and their durability.
“Question: What is the state of thinking on the life-span of carbon forks? Will they last forever, show signs of wear or should they be replaced after some span of years/use? I’ve had a Time fork in my old Merlin since 1998. It’s lived through a few race crashes and seems as good as ever, but I still have trouble regarding it as something as long-lasting as a metal component. Thoughts?–Jon”
Manufacturers’ replies:
From True Temper:
“We are confident on the long-term durability of our forks because we test far beyond the ASTM test standards for fatigue life on forks.
We have two types of fatigue tests:
1) ASTM
2) Ramped load testingASTM standards call for a load of 170 lbs. applied perpendicular to the steering axis, both pushing and pulling for 50,000 cycles without failure.
At True Temper, every Alpha Q model is tested to 250,000 without failure before a design is considered acceptable. Also production models are tested periodically for quality control.
True Temper’s own test is also used on every new model and in routine quality checks. Our test is a ramped load, meaning the load is increased periodically until failure occurs. Starting at 180lbs, the load is increased 45 lbs. every 5000 cycles. Every fork will eventually break. Strong forks will last more than 10,000 cycles with a load of 270 lb. But our minimum standard begins at over 15,000 at 315 lbs. for road forks and 18,000 for cross forks and tandem. But our production forks are stronger than that, often going into the 20-25K range and beyond at loads 0f 360-405 lbs.
Obviously, crashes are uncontrolled events and it is not easy to guess what loading was applied to a component by the speed or violence of the crash. After any crash it is important to thoroughly inspect the frame and components for visible cracks, dents, and bends. An Alpha Q fork that has been damaged (usually evident as a crack) should be replaced.
–Bert Hull
True Temper Sports”
From Kestrel:
“On the lifespan issue, of course the person should contact the manufacturer regarding specifics on the product in question. For carbon forks in general, there should not be any limited life span, as carbon composites themselves are not subject to fatigue failures as metals are. So the fatigue life of a properly made carbon composite is “infinite”. Example, in Kestrel’s case, our forks (as with all our carbon products) have a lifetime warranty and are designed and tested to last a “lifetime” of use for the given product…
–Preston Sandusky
Sand Point Design (Kestrel Bicycles)”
From Easton:
“There are two failure modes that could cause a fork to fail, fatigue or impact. Questions about life span are really questions about fatigue life. How many cycles can a fork survive before it is tired and worn-out? The good news is the fatigue life of carbon fiber is immensely more than that of metals. While the writer expresses concern about his carbon fork lasting as long as a metal component, there is nothing to worry about in terms of fatigue life on a composite fork.
The most likely cause of failure for a composite fork would be impact damage sustained from crashing. Most of the time any damage to a fork from a crash will be visible. Cracks can be seen. We would recommend that the fork be periodically inspected visually at the drop out area and along the fork legs to look for cracks or depressions in the material. Any fork that shows signs of cracking should not be ridden and replaced immediately.
In general terms, a component made from carbon fiber will far out-last a component made from metal.
–John Harrington
Easton Sports”
A Technical White Paper on frame materials written by Calfee Design (founded by the owner of Carbonframes – which made 18 frames, ordered by Greg LeMond, for Team Z) explains more about carbon use in bicycles.
“Carbon fiber frames first appeared in the mid 1970’s. The number increased in the 1980’s as more carbon fiber frames and a few components began to trickle into high-end bike dealers and parts catalogs. But these efforts were mostly limited attempts to save weight and often lacked careful engineering and commitment by the manufacturers. The lasting impression of most carbon fiber products was that they were quirky, flexible, fragile, and very expensive.
Over the past fifteen years, several more innovative carbon fiber framesets have entered the market. These have successfully challenged metal frames in two areas of performance – weight and ride comfort. But even some early versions of a few brands also had a poor record of reliability. Multiple warranty returns to fix cracks, loose dropouts and other unbonded metal parts were common…
Composites have made many advances since the mid ’80’s. Resins, fibers, and epoxies are a lot stronger today. What is more important, understanding how to use these materials has increased tremendously, due in part, to development of sophisticated analysis programs. Composites are more than high-tech weight savers; they are superior structural materials that are revolutionizing the way we build bicycles. A well-designed composite frameset performs better than a metal one. After taking some tentative steps, it has become a viable material in the bicycling industry. A few manufacturers have taken the necessary steps, and have a relatively firm grasp on the capabilities, potentials, and limitations of composites….
Carbon fiber exhibits the most desirable performance characteristics of any of the frame-building materials explored to date. It can be designed to be laterally stiff under heavy pedaling forces and still be light. It can absorb road shocks well, and still handle crisply while delivering undiminished applied pedal power to the drive train. It can be durable and not subject to fatigue failures while remaining strong enough to stand up to unexpected impacts and torsion forces. It can lend itself to attractive finishing and resist corrosion or attack by the elements. And it can be formed in an attractive, functional way allowing it to move through air resistance easily.”
If carbon forks are so prone to catastrophic failure, why are there no high profile carbon bike or fork class action lawsuits circulating on the Internet? In a litigious society like the U.S. (i.e one where people frequently sue one another), at least one carbon fork manufacturer would have been sued out of existence by now. Instead, many carbon fork manufacturers offer a lifetime warranty on their forks. Just from a business standpoint, if the failure rate was high, they would go out of business.
Even if you hate or fear carbon, this video of stunt riding on a carbon road bike is fun to watch. It demonstrates the amount of abuse carbon can take.
Bottom line: regardless of frame and fork material, always maintain your bike. Periodically, have an authorized dealer inspect it. Exercise caution if you ride hard or crash. Never overlook the inherent danger in activities involving equipment. Take proper precautions to avoid unnecessary risk and don’t be immobilized by fear of equipment failure.
