rchan

I've recently purchased a new road bike to replace my old all steel one. I was a bit wary about getting this one because it had a carbon fork instead of a steel one, but I got it anyway, because I figured I can get the info about the average lifespan of this type of material on the Internet.

Well, since I am writing here, you can probably guess I couldn't find anything useful at all. Occasionally I'd find something about how many cycles a carbon fork would last, but that isn't very useful since I don't know how many cycles a fork will go through in one of my typical rides, and usually the info is about a specific brand and model.

Does anybody know what is the average life of a carbon fork in terms of years or distance? I average about 1800 miles a year, pretty low milage in the grand scheme of things. Normally I wouldn't be so concered if it weren't for the fact that unlike steel, which usually bends when it fails, carbon tends to snap. Or is my concern outdated? Do recent carbon forks have something in them that will keep them from failing catostrophically?

Any info or web site referrals will be greatly appreciated.

Patricia

I can tell you I've seen full carbon fiber forks that have 28,000 miles on them with no problem.
If you are using them for under 2,000 miles a year than it will probably last you the lifespan of the bike.

Xavier

I do not ride nearly as much as when I was racing Elite but I am basicly putting basic miles than most 'recreational' riders are putting. I have had an original AME fork (Not the True Temper) for about 3 years now. Been on 2 bikes and I am sure I will get many more years out of it.

Carbon forks shouls last many years of not crashed.

datlas 

Inspired by a recent posting of a cyclist getting rid of a carbon fork because it was "old," I decided to resurrect this thread. Plus it's Halloween so a Zombie post is possibly appopriate.

I have occasionally heard people say that their fork should be replaced periodically. One of my friends rides a Lynskey and he swears they told him to replace the fork every 4-5 years.

I suspect that a well designed CF fork should last indefinitely unless it's crashed or damaged.

Comments??

GhostRider62

Carbon fibre does not have a fatigue limit

I have two carbon forks with over 50,000 miles each on them. YMMV

eduskator

Carbon Fiber HAS a fatigue limit. It's physics. Everything deteriorates in this beautiful universe.

Not sure that OP will experience it though as CF holds its properties for a very long time.

big john

Well the OP was 20 years ago. Maybe we could find him and ask if he's still using the same fork?

fwiw I have well over 50K miles on one cf fork and about 35K on another. Also have a cf mountain bike which has been slammed around for 4.5 years.

Branko D

CF fatigues (like anything does which is light enough that you'd put it on a bicycle), the mechanism is different than for metals.

It will eventually become progressively less stiff, after which it will eventually fail. How long is that eventually depends on how it is made (it is the defects in manufacturing which greatly accelerate the process), how heavy you are, how often you bomb full speed into potholes and speed bumps and so on, but anecdotally, it's about as long as you'd expect a nice metal frame to last before it dies out of fatigue.

Here's some reading;
https://www.academia.edu/30520244/Fa..._Bicycle_Forks

base2 

Happy Halloween!
5E8F74B9-EED9-49E5-B2C8-508EC10D41B1 by Richard Mozzarella, on Flickr

Zombie thread, indeed.

The guys in Formula 1 racing do deflection tests on their composite parts. The purpose is to Suss-out the added flexibility of the 100's of thousands to millions of tiny micro-cracks in the resin matrix that cumulatively lead to a part no longer performing as designed.

For this to work, you need a reference point. This is usually the logged test results from the very first time a newly manufactured part is put in a test rig to be tested. As a part is put in service the micro-cracks accumulate & this is revealed by increased flexibility (deflection) under test load during periodic testing.

Carbon fiber doesn't assplode. It tends to fail gracefully. With careful examination the damage is detectable & actionable.

What we're talking about here is mode of fatigue failure. Steel, Aluminum, Titanium tend to fail at some stress concentration & then concentrate at the concentration.

Like so many other things, it's down to design & execution.























(...and of course catastrophic failure is by definition: catastrophic. This comes from exceeding engineering designed capacity. That's not a question of material, that's a question of designed capacity. Take that up with the parts engineer. )

datlas 

Thanks for the Zombie updates. I don't know if OP can chime in.

My Habanero has about 60K miles on it, as does the Ritchey WCS fork. I have no plans to replace either. I am suspicious the Ti frame might fail before the CF fork does.

Happy Halloween!

GhostRider62

I did not read the references. If carbon fibre lasts on fighter jets, F1 cars, and commercial aircraft over my lifespan, in effect it does not fatigue. The resin? That is a more nuanced discussion. But I have a 30 year old fork hanging in the garage in the sun and it is still holding up.

A bigger issue is probably the extreme light and brittle layups being used where even the bike rack clamp on your car will damage the toptube permanently.

Branko D

Ritchey CF forks seem like a seriously beefy piece of fork. I was highly impressed with the build quality inspecting one, and I'd wager the steel frame it's on is going to die sooner.

The CF fork on my road bike doesn't look nearly as well built as the Richey one, but I still don't fuss about it. The frame and fork are going to get replaced eventually - I told myself it's fine to treat myself to a new road bike every six, seven years or so - or I'll crash hard enough that it'll need replacing.

Branko D

Well, I'll be turning 40 next year, so by the time I finally hang up the wheels, I hope the current commercial aircraft and fighter jets will be binned old junk. They do go through inspections and so on and so forth, and the QC is miles ahead of bicycle manufacturing. It's the forks with manufacturing defects which are fairly short lived.

GhostRider62

Interesting.

Having spend almost 40 years working in Quality Control, Assurance, Engineering, and Management and as an engineer, I don't know much about this stuff anymore, my brain is mush.

tomato coupe

F1 cars have to last only one season, and commercial aircraft must pass inspection every 100 hours.

Bob Ross

Okay, how about the telemetry antenna masts on the Voyager spacecraft? They've had to last 45 years and counting, with no possibility of inspection after the original deployment date. Currently moving at >30,000 mph and still working.

Of course, there aren't any potholes or garage doors in space...

tomato coupe

Those masts are subjected to zero stress, and speed while traveling through space is irrelevant.

thin_concrete

No F1 car lasts an entire season though. Whether practice, quali, or racing, it’s going to get damaged to the point it’s no longer usable for their purposes (going as fast as possible; serviceable to the ordinary schmoe - maybe). Not to mention the upgrades over the course of the season. The monocoque they finish with is generally not the one they started with.

indyfabz

Fresh, not 20 years old.

Bacciagalupe

Good grief, how did you even find this thread? Or do I not want to know?


I've... never heard anyone say that, and can't imagine a manufacturer saying that. Personally, I wouldn't drop 2 large on a frame with a disposable fork. Or perhaps I should say, I wouldn't drop 2 large on a frame where the manufacturer has so little confidence in its own fork that they recommended a full replacement every 5 years....


Pretty much.

While the term "Retro Grouch" has slowly come to the surface of my addled brain, I find it hard to imagine that serious cyclists today have any concerns about CF... or road disc brakes... or hydraulic brakes... or electronic shifting, or any of the other innovations that stuck despite the moral panics over the impending doom of using them.

PeteHski

F1 is not a good example for carbon component longevity. I worked as an engineer in F1 (not a composite specialist, but saw a lot of it). Critical structural carbon components are typically proof tested every 1000 km. The two biggest issues (aside from a crash) in their case are stone chips and exhaust heat.

tomato coupe

Exactly. Which is why I objected to the idea that the longevity of F1 cars implies carbon fiber does not fatigue.

GhostRider62

My bike passes every ride. Inspection does nothing to increase the inherent durability of something. F1 cars crash, rocks hit them, and certain structures deal with a little bit of heat. Part of my bmw's structure is carbon fibre and it should outlive me.

I could be wrong but I doubt any commercial aircraft has its fuselage checked for cracks every 100 hours. Not even the new Marine One gets that treatment.

genejockey 

Also, moving at a constant speed in zero G, so there's little if any force in any direction on them.

datlas 

The search function is quite powerful if you know how to use it.

I suspect the folks that suggest a new fork every 5 years are the ones who sell forks. Kinda like the helmet manufacturers saying you need a new helmet every 3 years.