Carbon Fibre Bike Frame

I'm not going to be much help. And remember, there's more to your frame than just carbon fiber. Something has to hold that fiber together. So, you aren't dealing with a homogeneous substance, as in a metal.

I worked with carbon fiber assemblies during the '70s. (Aerospace, not bikes) What I did was, at the time, "state-of-the-art". That was only 30+ years ago. My gut feel is that the state of the art has advanced, but not to the point of a lifetime warranty.

Metals are more mature and well known. Less prone to environmental influences and degradation. Easier to join, although I don't know if plastic bikes are bonded together.

Two years seems a short time for a well maintained bike.

I do not claim that this is expert advice.

Good luck.

there was a post of carbon fiber frame on a bike here on CR4, did you search here yet, it was about a year and a half ago....

did a quick search and found the one I was thinking about Composites Experts for Failure Postulation

Keep the stresses low enough and a steel frame has infinite life.

Carbon has a catastrophic failure mode. I got a significant dent in my steel tubed frame 18years ago and it still works fine.

What I worry about is the latest fashion of straight blade type forks. The original evolved steel design had tapered bent tubes for the front forks, why?? For suspension and to remove the stress concentrations. This logic seems to have disappeared and maybe this is why it is suggested to get rid of it in 2 years. Every time I hear a good sized stone hit my front tube I think "thankfully that is not a carbon tube"

Try a bamboo frame.

http://www.calfeedesign.com/pages/bamboolarge.php

in the Philippines, in our weather, this will remain a novelty, and no serious cyclist will use this.

we know the limitations of bamboo. how? we live in 'em.

when a bamboo fails, it shreds at the break. being impaled in the backside with so many bamboo toothpicks will be very nasty.

Sounds to me like they simply want to sell you another expensive bike in two years. The leaf springs on Corvettes are Carbon Fiber, and I don't see them failing catastrophically. Same with the aerospace applications such as turbine bypass fans and airfoils and such.

I don't deal with people who look at me and think "sucker". I find someone who respects me as a customer. I would suggest you do the same.

But let us analyze what would happen if the frame were to fail catastrophically. The largest stress concentration I would expect would be where the frame and front fork meet. So that is where I would expect any fatigue to appear. So what would happen if it failed catastrophically, you'd go arse over tea kettle and execute a classic faceplant on the pavement, not unlike what happens if you were to hit a curb or a rock or something. I presume you wear proper protective gear at all times, so what would happen? a bit of road rash, maybe a concussion at worst. I suppose if you were to fall wrong and land just right you could do some really serious damage but the odds are pretty long. But I would expect that the frame would be showing signs of fatigue far before this happened. when carbon fiber parts fail, what usually happens is the epoxy binder fails and the fibers bunch up like rope then start to unravel. so they don't fail the way metals fail, they kind of crush internally, but the fibers are far stronger than the epoxy so the joints loosen before the fail completely. you should have LOTS of warning.

I say ride it until they come out with diamond or TTZ fiber composites and save the 3k.

Two comments:

1. Have you ever been on a bike where the frame failed to know what effect this has on the rider? In the middle of a long descent that would be rather deleterious to ones health. Don't think I'd be so cavalier about recommending riding to failure.

2. the manufacturers have already figured out the head tube/frame joint gets the most stress and this area is absolutely huge on a carbon fibre bike compared to a classical steel frame, so the I figure the most likely failure is probably top tube/seat tube or seat stays/seat tube, as these areas see a good deal of stress, but are usually rather dainty looking. Don't forget the fork itself either, as I personally popped one of these inside the 2 year period. That's the least substantial looking carbon fibre part on a bike, especially the connection from the carbon fork to the post that goes through the head tube. Thats a very stressed area. However, for the record, I took out one of the fork legs on a good bump in the road. (pot hole)

Well done.

Your point about compressive strength is well taken. If one side of a tube is in tension, the other side must be in compression.

Let me tell you about my take on the cutting edge technology - the bike was perfected about 30 years ago, and save for disc brakes, has only become a source for continued income for the parts manufacturers since then.

I was re-introduced to cycling 10 years ago and went through all the latest equipment in that time period. I had a 3" travel fork, then 4", then 5". I had a solid rear end with suspension fork, 3" rear travel with 3" travel fork, 5" rear travel with the 5" fork, carbon road bike, carbon forks on "hard tail" bikes, and so on. The 3" full suspension bike has weinered shock mounts. The 5" full suspension bike broke the top tube at the weld point from stress from the shock, in 2 years. My son has my carbon road bike, since I never could get into the feel of the ride. As mentioned in another post, the carbon fork on the "hard tail" self destructed in about 2 years. Several of the after market suspension forks have long since worn out.

I mention again, I am months from being 60, so no crazy stunts were done on these bikes. None of the bikes were ridden continuously, as I have a stable of bikes. All bikes were major US brands and cost over $2000 each.

Know what I ride now, and am quite pleased with? All my current most used rides (5 of them) were built prior to 1990 and yes, some parts have been up-graded, but most are still functioning quite nicely. The prime example is my 1983 Schwinn Super Sport (Panasonic built). I had to replace the bearings in the bottom bracket, the seat, the bar tape, the chain rings, the free wheel, the chain, and the brake pads to get it back into top shape. The bearing races were all in great shape. The headset bearings were cleaned, greased, and put back into service. I have had to replace the headset on all the new bikes I've bought inside of 6 months. Even the pedals are in fine shape, despite the bearing seal drying up and falling out. I'll just keep them greased well and they'll function fine. I have no problem with friction shifting, so even the shifters are just cleaned and remounted.

Don't know about the frame, but I killed a good ($400) carbon fibre fork in about 2 years. Some other facts need to be presented:

1. I weigh about 250 lbs - bad for fork

2. I am what they call a hammer head - no spinning like Lance - 60 rpm and lots of pulling on the handle bar which has to affect the fork

3. I have 8 bikes so the fork in question was used on maybe 15% of my rides - not much wear on fork

4. I do not do crazy stuff as I am nearly 60 years old - easy on the fork

When the fork went it was spectacular - I thought someone had shot a gun beside the road or a tire blew out. No horrific destruction, just a lot of noise.

So you can decipher my data as it applies to your frame.

When the fork went it was spectacular - I thought someone had shot a gun beside the road or a tire blew out. No horrific destruction, just a lot of noise.

wow.....people pay money for a ride like that.......more to witness it.

How was the tumble?

Money wasted - definitely - see post #10 by myself describing what I now think of modern bike technology.

there are some things I like about modern.......a more comfortable seat being one of them.

Are you serious? Have you ever ridden on a Brooks? (circa 1895 design) I have a collection of 29 modern saddles for sale - all 8 of my bikes have either a Brooks or a Selle Anatomica leather saddle.

your right, its not so much the saddle but the fit and adjustment also

Well thank you all for your advice. I have three carbon bikes, a "best" road bike, now approaching two years, only comes out in the summer(Alu bikes are used in winter). A time trial bike, about 6-months old, obviously gets much less use than the general road machine. And interestingly, a cross-country mountain bike(A Scott Scale Ltd, for those in the know). Why buy a carbon mountain bike if I'm concerned about the integrity of carbon you may ask?!! Well, I originally always swore by aluminum mountain bikes, but got the chance on a manufacturer's demo day to ride a carbon bike. Impressed was not the word! This thing glided over the rocks & ruts, it took off up the climbs like a rocket. There was just no comparison at all!

So far I have had no issues whatsoever with any of my carbon bikes, despite my weight- 170-5lbs.I certainly didn't believe the bike shop. As I said, the bike shop may tell you to change your bike for safety reasons….Then promptly but your bike up for sale in the quality used bike section. "Only a year old, hardly been used" Etc.

So I came on here to see if I could get a more of a qualified view on the subject. And I think I'm reasonably satisfied that under the manufacturers definition of normal use, the material should be fairly reliable. But from various posts and links on here it would seem that forks are particularly vulnerable to stress compared with the rest of the frame.

Rorschach: A good going over of my three carbon bikes shows no visible signs of what you described happening.

It's funny but a lot of the older cyclists, I would say 60+, still swear by steel frames (And yes, Brook's saddles too). Some of the older club riders are still riding on frames that they acquired new in 1960 or 50 something!! They swear by these comparatively heavy things, and used to ride them to some serious triumphs back in the day, with the medals to prove it. Which leaves me wondering if us younger riders have become softer over the years?!!!:-/ A lot of the older guys won't entertain all this "new fangled" frame technology at all! But somehow steel's just not sexy enough! Hmmm.

Dear Carbon Frame Owner, I own a bike shop in Seattle, and early on I had Boeing engineers as customers and friends. Was the best man for one of their top carbon guys working on the B-2. There are pros and cons for all materials, unfortunately the market in the U.S. is for the lightest, lightest, anything to play what I call the "gram" game, consumer be damned!! After 37 years of seeing high end steel, heat treated 6061 or 7075, Ti alloys, and obscenely light carbon, I tell customers either high quality steel like Columbus Spirit or Life niobium alloy, or titanium alloy. Skip aluminum and carbon. Why? I'm glad you asked that question. Aluminum, when fatigued, the strength goes to zero. High end steel, when fatigued, the strength goes to 50% (thanks to my boeing customers). The only practical material to test ride is aluminum, carbon, or titanium. I am not sure about scandium. I was teaching a class on wheel building when a student, a carpenter, showed me his Titanium frame, made by Ti-Cycles, which was hit by a car on the left rear seat stay. He wanted it straightened without paying $650 to replace it. I've straightened hundreds of frames(steel of course), so I told him we could try. By locking a bare rear hub in his frame, without spokes or rim, making the rear triangles of the seat and chain stays rigid, I swung a sand filled mallet to bend the stay back inline. I spent two summers as a roofer, and I know how to swing a hammer. At first I swung firm hits and checked with a straight edge, nothing moved. After 10 minutes of swinging as hard as I could with three guys holding the bike in the stand steady, and I mean full blown swings that would have knocked a steel frame two feet sideways, it moved 1mm, maybe. I broke out the old fashioned rim puller with pieces of wood installed as protecting shims and pulled the stay almost perfectly straight, with the small dent from the car impact left as is. That day I learned to respect the strength of titanium. The EU now has fatigue tests for carbon bicycle frames and components to be sold in the EU, sadly, the U.S. lags behind in these safety standards. Stress risers is where carbon will fail, usually in the seat tube/seat binder area. And I have seen too many cracked forks in carbon, though the designs have greatly improved. The main tubes are getting too thin on carbon, ride them, but don't ever crash. What about the uv light with the epoxy?? Too much bare carbon fiber is exposed to sunlight, damaging the tubes. They should have all carbon painted for protection, but the market people always win. There are some great deals on new Ti bikes, I think made by Shanghai Aerospace, though it's suppose to be an industry secret. Check for the tig-welded water bosses, not riveted like Lightspeed or even like the Seven I own. What do some pro racers use as their personal bikes? Titanium, though their team is given carbon bikes. Shhh, don't tell, titanium prices will go back up. Test ride if you can, and don't get your wheels too light, they won't last, the sidewalls are way thin. Isn't that where the brake pads ride? Those market guys know the consumer will have to replace rims sooner when they are thinner. Feel free to ask questions.