genejockey 

My wife was not happy about my interest in expanding my stable, because she thought I'd be paying >$1000/bike. When she learned how little a C&V bike costs - TO BUY - she essentially gave me free rein. And because the parts are all relatively small individual purchases, she never realized the bike I paid $150 for eventually cost an additional $500 in bits......

spelger

so that's the secret.

genejockey 

It works for me!

venturi95

Only a handful of people have been killed or paralyzed by carbon fork failures, just ride' em until they snap.
Why Carbon Fiber Bikes Are Failing - Outside Online
Police eye Cervelo fork in fatal crash | Bicycle Retailer and Industry News
I have recently replaced the fork on my new-to-me, low mileage 2005 Litespeed Tuscany with an ENVE 2.0 fork. I have no actual idea of this bike's history of use/abuse or crashing. The guy who sold it on Craigslist seemed nice enough and honest, but I don't even know if he was the original owner.
A couple of years ago I bought a 2011 Jamis hybrid with a carbon fork for $200 on Craigs list. The guy who sold it was not a rider. He must have been 6 foot 2 inches, older than me (I'm 64), and weighed 250 pounds. The bike is 19" with a radically sloping top tube, perfect for me, not even close for the geriatric bruiser who had it before me. Again, the bike's history is unknown. The all-carbon fork weighed 620 grams; the bike got a Soma Fabrications steel fork upgrade.
I ride for enjoyment. Worrying about dying (or worse) due to a lightweight Fiber Reinforced Plastic bicycle fork breaking is not enjoyable.

Polaris OBark

Is that the Enve fork that was recalled? Maybe you could have got a new one for free.

venturi95

I just got it in the beginning of September, I hope not. But thanks, I will investigate it.

Polaris OBark

Sorry, that was an earlier one:

https://www.cpsc.gov/Recalls/2016/EN...-Bicycle-Forks

Camilo

Yea, me too. I'm seeing my brain and most body parts reaching their fatigue limits. The fault lies with several factors: age, design, use and misuse.

Actually, it is the point where N+1 =/< S-1 (not sure how to do that "less than or equal to" notation)

Oh, come on. Everybody knows this, it's just common sense. That and paying cash for parts whenever you can.

easyupbug 

It is not. As a young engineer I worked at Thiokol (rocket motors) and can tell you carbon fiber does not have a fatigue limit (the number of cycles that a material survives with a given stress amplitude) as said but will degrade from fatigue, differently from metals that have a fatigue limit which typically shows up as a surface crack. Fatigue in a carbon lay-up can break fibers, cause resin bond to fiber failure or cause fabric layers to separate. Fortunately these conditions can usually be heard if one taps on the fork or frame and the sound is dull, more thud rather than the sharp sound one would expect.

Jack Tone 

So aluminum has a worse fatigue limit than carbon, right? I bought a Cannondale 3.0 frame about 30 plus years ago. It came with an optional "new" for Cannondale, aluminum fork. I'm still riding that bike on rough, pot holed roads. I'm probably staring death in the face just walking into the garage and looking at it.

datlas 

Branko D

Years don't mean anything for metal fatigue.
​​​​Two years at 15000 km a year and thirty at 1000 km a year is the same thing.

datlas 

Agree. But the question is, what is that "thing?" and should people worry about it?

My suspicion is not much to both questions.

79pmooney

The flip side here. Replace that fork (any fork) BEFORE it breaks. I didn't. It cost me my education, half a decade of my life, a lot of money and far more in earnings after. The longer your fork has gone, the more important this is.

Failure mode is a real part of this. Forks that suddenly become two or more separate pieces are far more dangerous than forks that do it slowly. My three fork failures: Aluminum. Broke at the crown without warning. Starting under the crown race so finding it through inspection was impossible with either X-ray or removing the race. (See the preceding paragraph.) A cheap steel fork that broke clear across mid-blade. I noticed it riding home from work. Bike was still ride-able with just one blade so I continued the next mile home. (Bike had a LowRider rack. Break was just above the U-bolt - no braze-on. The LowRider might have helped stabilize the lower blade after the break.) The original fork of the custom ti bike of my avatar photo. Columbus SL built by a master and plated with nickle. Never got the required heat treat to drive off the embedded hydrogen atoms.

At 8000 miles, that SL fork cracked 2/3s around just below the crown on one blade, 1/3 of the way on the other. I was very lucky. That was happening as I started down a 2000' descent. (I had someone looking after me that day. Plan was to bomb the fix gear down in 42-12 and fly around a corner I love but have to brake hard for upon entering. Perfect pavement, banking, never debris so a late hard brake is a blast. Well, at the top of the mountain, I had issues with the lockring, tiny cog and chain. It kept going loose, then tight. Finally just set the chain to too loose and moseyed down so as to do now damage to anything 2 weeks before Cycle Oregon. 15 miles later the bike started bucking ever time I touched to front brake. Got home, saw the cracks and walked into the house shaken to the core. BTDT.

The fork you see in that photo is a rush job replacement. 531 with a deeply scalloped crown. Conservative to the max. Builder finished the build 7 days after it broke. (He had to order the 531 and it took a while.) Painted it with model paint I picked up at a hobby shop. A week later it was off the rural Oregon and that photo.

To this day, I consider that avatar bike a really "good" bike. It saved my butt. Provided a trivial mechanical when I really needed it! That fork breaking wasn't its fault. You simply have to heat treat high strength steel alloys after nickle plating. Common knowledge in the plating world. Plater knew. His rate for the heat treat was $60. He said nothing. We'd have paid it happily if he'd spoken up. (And shared blame here - I chose a minimalist investment cast crown that the builder assured me was plenty strong. He landed some SL blades (I was thinking 531) and I said yes. So - that crown with no scallops and thin tubing = a lot more stress. Builder knew that and did absolutely beautiful brazing. (I go t to see what no one ever sees - the braze around the inside of the crown. Looked like a perfect machined radius except with the matte of a braze that's never seen a file.)

My forks now - (1) and perhaps two more are 531 on my three customs. (Non are "stickered". Peter Mooney wouldn't when I ordered mine unless you paid extra so he could select what he felt was the best tube for the application. I simply trusted TiCycles on the next. The third custom is that avatar.) I also have a stock 4something 1983 Trek. Hi-ten probably. Pro-Miyata with Miyate Chro-Mo. Raleigh Competition stickered 531. Only slightly radical fork blades are on the Miyata which are squeezed and slightly aero but Miyata's record on high end '80s race bikes is rather impeccable.

I'll pass on (hopefully from other causes) before I ride a CF fork because of its failure mode and I'd always have that "what if" in the back of my mind and in my dreams. If I didn't know the consequences first hand it would be a different story. (And like that fork of mine that cost me so much, CF forks have workmanship that is critical where it cannot be seen without testing or destruction. Doesn't help that I used to build fiberglass boats and know first hand the shortcuts that get you to break time sooner or allow more to be built and keep sup' happy.)

Camilo

Am I missing something? Was it a CF fork that failed and you were hurt? I see three failed forks mentioned:

My three fork failures:
Aluminum. Broke at the crown without warning.

A cheap steel fork that broke clear across mid-blade. I noticed it riding home from work. Bike was still ride-able

Columbus SL built by a master and plated with nickle. Never got the required heat treat to drive off the embedded hydrogen atoms....At 8000 miles, that SL fork cracked 2/3s around just below the crown on one blade, 1/3 of the way on the other. I was very lucky....Got home, saw the cracks and walked into the house shaken to the core

Sounds like the aluminum one failed catastrophically? But if it or one of the others, why don't you trust carbon fiber forks? I'm not a shill for CF forks - except i don't see any evidence that they're any more "dangerous" than any other material. But just curious about your experience. And sorry to hear about the bad accident!

Branko D

If anything, fatigue in composites is more of a gradual widespread degradation, which could potentially get noticed, then a localized crack appearing and spreading until the whole thing falls catastrophically which is how metals die out of fatigue.

The high profile catastrophic CF steerer failures have generally been a consequence of engineering blunders (associated with more, let's say avant-garde designs) or user error (overtightening with too much spacer above the stem leading to clamping unsupported carbon fiber as the compression plug isn't long enough). A conventional CF fork where the manufacturer isn't trying anything weird is a well proven design.

PeteHski

What are you trying to say again? I'm confused.

Camilo

My guess is that he was saying he's had three metal forks fail, one catastrophically, and because of the metal fork failures, distrusts CF and won't use it. I hope he clarifies because I'm genuinely curious.

PeteHski

Yeah, seems like a cycling disaster zone!

cxwrench

Exactly. "I've had 3 metal forks break so I'm not going to ride carbon because it's some weird magic I can't see and therefore don't trust". Ok...

procrit

Wait till he finds out commercial jets use lots of carbon fiber and composites for frames and fuselages that are subjected to harsher conditions than a typical road bike frame.

easyupbug 

We all do some degree of risk assessments in our daily lives which are made up of likelihood and consequence. I think it completely reasonable that having 3 failures and one with a horrific outcome would make one extraordinarily risk adverse and perhaps make judgements that seem unreasonable to us who believe the probability highly unlikely and the severity potential at an acceptable level.

Camilo

But, he's had two steel forks fail and still prefers steel to carbon fiber which he has no experience or explained basis for mistrusting. I don't question his right to make the risk assessment for himself, and it certainly is not usnusual or bizarre to prefer steel over any other fork material. He doesn't need to justify his choice at all, but it's just confusing. He gave such a detailed analysis about the three metal fork failures he experienced but not any reason to have such a suspicion about carbon fiber. None of ths would be discussed (at least by me) if he'd just said what countless other people have said about their mistrust of carbon fiber forks: I prefer steel.

Personally, this just seems like a time warp back 20 years or more.

easyupbug 

Your points are valid. I did some work as a young engineer at Thiokol labs and while I fully support validating carbon fiber integrity with simple pinging tests for carbon matrix composites finding a metal crack propagation point might be viewed as easier.ate ne

t2p

agree

the largest most powerful jet engine features carbon fiber composite fan blades ( w/steel or titanium blade tips (can't recall)

some of the aircraft that use this engine have all composite wings