Carbon fibre frames

Mancunian Lee · 04-06-2005

These seem to be getting more and more popular dont they?

i would of thought these where a bad idea considering one mistake and hit the bike at a funny angle and it will shatter into tiny pieces wouldnt it?

Anyone got any thoughts?

SuperNewb · 04-06-2005

The technology is always evolving and does get better down the road (usually)

nnn · 04-06-2005

Not exactly a particular 'angle' but carbon fibre can be prone to sracks from hitting other things and once its cracked no matter how small it's pretty much useless.

Cucucachu · 04-06-2005

Shatter in pieces? I've heard of catastrophic failures (i.e. sudden breakage) but don't think CF is as brittle as glass. You can test this theory with the purchase of a CF seat post. They break real nice!

Yeah, like what the mate says below! Yeah, like that...broken clean off.

Mancunian Lee · 04-06-2005

Quote:

Originally Posted by Cucucachu

Shatter in pieces? I've heard of catastrophic failures (i.e. sudden breakage) but don't think CF is as brittle as glass. You can test this theory with the purchase of a CF seat post. They break real nice!

i didnt think they was that brittle mate!! the stories ive heard are of people hitting big rocks maxing out their suspension and the forks have broken clean off leaving sharp shattered edges along the break!!

On paper CF seems the ideal material for a bike frame tho.

Master Shake · 04-06-2005

Quote:

Originally Posted by Mancunian Lee

i would of thought these where a bad idea considering one mistake and hit the bike at a funny angle and it will shatter into tiny pieces wouldnt it?

No.

Carbon frames aren't carbon, they're a composite of many different materials, and a plastic or resin (like plastic anyway) filler. The outer layer on a good composite frame or component will usually be spectra or rouging or kevlar or SGlass or something to protect the structural carbon below. This is because carbon is indeed brittle, but not like you'd expect. It doesn't "shatter" really. It's fiberous, and when it breaks, it's sort of like breaking a stick of celery, but flakier... anyway. The stresses concentrate at weak areas, much like a weak link in the chain will break first. The stress piles up there, usually causing some damage, making it even weaker, causing more damage, till you have a failure point. Grooves, sharp corners, angles, seams, scratches, anywhere there's an interruption in the surface becomes the weak link, & are called stress risers (the amount of stress rises on these features, see?). There's an entire science behind Notch Sensitivity. It's a big deal. A notch will alligator out till your frame rips open or your cranks crack, or your bars snap, etc... there are ways for this notch sensitivity to become a problem. A big one is galvanic corrosion. Companies who do a quickie job of bonding aluminum fittings & inserts into carbon amaze & delight on the showroom floor. A full carbon Trek for $700! Yippeee. Yes, well, alum reacts rather poorly I'm afraid, when in direct contact with carbon. So this is where frames get more expensive.

A carbon seatpost goes into your frame, and gets pinched by the cheapass slotted seattube method everyone's been using forever. Tighten that skewer or bolt too much, and you'll cause the edges of your slot to indent into the post. That poor little legth of seatpost has to support all the load & impact loading your entire frame has to. Putting a notch in such a critical place is taking the express train to tire-induced friction burn on ass town. Still, everybody does it. Yep, and everybody breaks em too. You just accept it. Seatposts break. Carbon ones doubly so. Frames break too. Same goes for cranks. And frames. The less expensive your carbon frame, the higher the failure rates will be. Doing carbon right takes time, & there's no way around it. Also, typically, the bigger the company, (like the one I work for. Anonymity is grand.) the cheaper their carbon will be, regardless of the sticker price. This is due to a few things, but one very big one, is that when you get very big, there are exponentially more hands in the pie, and keeping your retail price competitive means the cost has to come out of somewhere, and it certainly can't come out of payroll, so you find the cheapest possible way to get the job done, and charge as much as you possibly can for it in the end, and hope that there's a penny left in it for you after the dealers have taken their 40% margin, the reps have taken their 20% cut, the distributors have taken their 30% margin... Welcome to capitalism. We've become a nation of suck-eyed jackyls skimming off the top. But who suffers? The not-I's go all the way around till they find you, sitting in the middle of the trail on a broken pile of carbon slivers and aluminum shards... Price driven markets kill innovation. But in a dangerous sport like this, they kill people. But you people keep buying what we're selling, so as far as we're concerned, money talks, and it's your own damned fault.

Still happy you asked?

Mancunian Lee · 04-07-2005

Quote:

Originally Posted by Master Shake

Still happy you asked?

why wouldnt i be?

I didnt know that about CF it sounds like it has similar properties to fibre glass in the way it breaks! i suppose CF handlebars will suffer the same fate?

Tig · 04-07-2005

Quote:

Originally Posted by Mancunian Lee

I didnt know that about CF it sounds like it has similar properties to fibre glass in the way it breaks! i suppose CF handlebars will suffer the same fate?

I've seen carbon bars crack at the stem clamp, but usually due to over tightening the clamp bolts and/or a major crash. I've seen a few CF seatposts shear. At the shop I used to work at, we took a cracked pair or road bars out in the back parking lot to try to destroy. It took much more abuse than anyone expected! You could throw them against a wall or the ground and they only suffered surface abrasions. We banged them over and over against the edge of a dumpster but they wouldn't crack until about 2 dozen hits.

Still, I wouldn't want a CF frame for MTB riding. I can't see spending so much for so little longevity. Pro's on factory rides don't have to worry since they get them for free, but not us working people.

I ride a CF road bike, but crashing is something I manage to avoid for several years at a time. I ride a Bontrager CF seat post and an FSA flat bar on the MTB, but I only weigh 135.

Master Shake · 04-07-2005

Quote:

Originally Posted by Tig

...At the shop I used to work at, we took a cracked pair or road bars out in the back parking lot to try to destroy. It took much more abuse than anyone expected! You could throw them against a wall or the ground and they only suffered surface abrasions. We banged them over and over against the edge of a dumpster but they wouldn't crack until about 2 dozen hits...

Put a static load on em of a about 1000lbs (a 200lb rider hitting an average sized bump) & then do it.

Poof! Good fun with a handgun...

Pete

rzozaya1969 · 04-08-2005

I think the question is whether someone should or shouldn't get a carbon frame. I think it depends on 3 things:

1. Price
2. Use
3. Weight

Regarding price, well, it depends on your wallet, but when comparing two similar frames, and one of them is carbon, guess which one will be more expensive. It's just how much you want and can afford to pay versus making the bike lighter or heavier.

Use, I don't *think* there are carbon freeride beasts, jejeje. Now, I do believe carbon is great for paved roads. Now, those may be the 2 extremes, how do you use your bike? Do you do drops? etc..

Weight, are you a skinny biker, or a clyde? I'm heavy @ 200 lbs, so I don't want to use carbon (I have already notched my firstandonly carbon seat post on the first ride), but most riders weight less than I. I think that weight influences use.

Now, have anyone used the Titus Exogrid frames? They sound nice but expensive.

PinkyBrigade · 04-11-2005

My friend rides a full carbon frame and hasn't had any problems with it, I am not completly convinced, but they must work.

Master Shake · 04-11-2005

Simply put it goes like this:

If you spend the money to do it right, you can make a carbon composite frame stronger per weight than a metal one. That's not to say that if you spend the money, you WILL get a stronger frame. If you buy an pricey carbon bike from a company that turns em out by the thousands, you're getting a cheap carbon frame that has a bunch of markup to pay for fancy advertising campaigns. Your odds are better buying from a company that specializes in and actually makes/is responsible for it's own product. If you want cheap carbon, you're putting more than a few hundred dollars at risk. It's your front teeth on the line. If you're not willing to pay for quality, you will not get it. In the end, it comes down to: you can get what you pay for, but you will allways pay for what you get.

Expensive carbon: Good or bad, depending on the ethics of the company.
Cheap carbon: Bad.

And that's it. Guys like Calfee & Trimble are doing good work. The 29er forum has some interesting threads up at the moment.

INVERTED -4 · 04-12-2005

Carbon fiber can be very durable!
The Trimble inverted 4 frame was extensively proven on the norba circuit in the late 80s early 90s.Stock xc frames were used for both down hill and dual slalom events with no major problems. Even earthquake Jake Watson rode one in the down hill.