From the article:
If you are a bike rider it is important to maintain your light bike by performing a fork replacement every 4000-5000 miles
Oh my goodness what a bunch of baloney!!! When this came up on the tandem forum, Craig Calfee himself posted that he had recently heard from a couple of different customers of his carbon bikes who each independenly said he had over 130,000 miles on the bike and it handled just like it did brand new.
Carbon does not fatigue like the metals do. If it makes any difference, the only fork I've seen break on the road was aluminum. There can of course be a manufacturing defect, but even most carbon failures, whether from a manufacturing defect or an accident, give plenty of warning so you can stop riding it before it causes an accident. BTW, if you get in an accident, it's more important to replace aluminum bars than it is carbon. I know people who have broken aluminum bars suddenly and it's usually pretty nasty. I know one man who broke (actually just fractured) a carbon bar, but it was not catastrophic. It held on, but he couldn't put pressure out at the end anymore as it was extremely flexible at the break area.
Our younger son was going 25mph a couple of summers ago when someone turned illegally in front of him, and, having only one hand on the bars and a water bottle in the other hand, he sailed right into the car. He went flying, broke his collar bone and his nose, but I sent the frame and fork to Calfee for their thorough inspection and tests, and they found no damage to the carbon itself so he's still riding the same bike with a lot of new components. The force of the impact was so great that it even deformed the front hub shell and bent the axle a little.
We have a friend who was in a nasty accident a couple of years ago on his carbon Trek, and hit the right seat stay on the curb hard enough to have a thick 5" bundle of fibers sticking out. He keeps riding it, and mostly in the local canyons. He says he has some stuff from his son to fix it but hasn't gotten around to it. I hope I can get a picture before he fixes it, because it is truly impressive. His son works at a place that makes carbon fiber rotor blades for military helicopters, and says they have to be able to take 100 hits from a .50-caliber machine gun without failure.
Age and fatigue themselves are non-issues with carbon. Lennard Zinn asked CF fork manufacturers about the life expectancy of the product. Here's what they said.
Preston Sandusky at Kestrel says, <quote> 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".
Ming Tan at Look says, <quote> There is no limitation because carbon has a natural flexibility. It can be used a hundred years while maintaining the same stiffness.
Fulvio Acquati at Deda says, <quote> Carbon lasts longer than metal. Only love is stronger than carbon.
John Harrington at Easton says, <quote> The good news is the fatigue life of carbon fiber is immensely more than that of metals... there is nothing to worry about in terms of fatigue life on a composite fork...In general terms, a component made from carbon fiber will far out-last a component made from metal.
No one has ever done any systematic, large-N, independent testing to verify manufacturers claims that carbon fiber is stronger than metal, but in theory it should be.
Bert Hull at True Temper says, <quote> ASTM 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.
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...Our minimum standard begins at over 15,000 [cycles] 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.