Mountain Biking - Mountain Bikes & Carbon Frames

Many "Roadies" are convinced that the best frames for a road bike are carbon frames - they are "lighter" and "more expensive", which in the "Roadie" world, means "better".

And, "lighter" makes sense when riding a bike UP a mountain. But what about the folks who enjoy riding DOWN seriously fast hills and mountains at high speeds? Of those whose riding involves a high amount of riding DOWN trails at high speeds, how many of your are riding on carbon frames? How many of your are using carbon handlebars?

When you are getting ready to ride DOWN an intense trail that requires experienced and skilled riders, what percentage of the riders that you see on the trails are riding with a carbon frame or a carbon fork?

And, if you won the lottery, and "money was no object", and you were looking for a bike that go DOWN any trail, at any speed, would a carbon frame be your first choice? Would a carbon handlebar be your first choice?

I don't trust it...at all...but living here I see lots of bikes...soo

Carbon bike = .25%...there is one. The BCD. I only saw it cause I knew the rider (by fame and another forum). He is both a freerider and dhiller and djers...smallish guy but super smooth...
carbon parts = 5 - 10% .... seatposts and bars, thats being generous btw I just think there might be some I missed along the way. Oh and on freeriders...none...I don't know any serious freeriders who use carbon anything...(ecept helmets and maybe visors...)

If money was no object I still wouldn't buy carbon. Have seen and heard of too many seriously bad accidents caused by them. Most of the guys I know who tried it, loved it....absolutely loved it...till the carbon breakage occured. Sometimes user error (tight bolts) sometimes after a crash (gauge) sometimes no reason at all. But scary and common.

I only know 1 person riding a carbon frame and he's strictly xc. It's an older trek. I don't know of anyone going big on cabon.

I ride a Giant Cadex CFM2 which frame is carbon Fibre tubes onto aluminium lugs.

I have had no problems with it, even when upgrading to suspension forks (the bike is a '92 model and was non-suspension geometry)

If money were no object I'd probably get a titanium frame

Forgot to add I only ride XC

I have Carbon Fiber Chain Stays on my bike (Cannondale Scalpel) But its an XC bike.. its realy nice but i wouldnt trust it on any big drops (bigger then 3-4 feet) i just dont trust something that flexes like my chain stays and doesnt snap that easily

They also make Carbon Fiber Cranks ( i forget who does... but if i find the link ill give it to ya) Carbon fiber is one hell of a way to save wieght... if your an XC rider then you should get as much carbon as possible on your bike :) (within reason)

I have Carbon Fiber Chain Stays on my bike (Cannondale Scalpel) But its an XC bike.. its realy nice but i wouldnt trust it on any big drops (bigger then 3-4 feet) i just dont trust something that flexes like my chain stays and doesnt snap that easily

They also make Carbon Fiber Cranks ( i forget who does... but if i find the link ill give it to ya) Carbon fiber is one hell of a way to save wieght... if your an XC rider then you should get as much carbon as possible on your bike :) (within reason)

FSA has carbon cranks

link me up Mael :)

I wouldn't ever own anything carbon for my mtb... people here have snapped their carbon handlebars, one guy got nearly impaled. I'm sure those are exceptions to the rule, but I beat the crap out of my mtb.

I doubt I'll ever own a carbon roadie.

I'm thinking Ti for both styles next time I buy.

http://www.fullspeedahead.com/fly.aspx?layout=product&taxid=52&pid=96

Only ONE rider on the forum has ridden a Mountain Bike with the main frame made with carbon tubes? Just one? Surely, at least two people have tried their luck on a carbon framed mountain bike?

There aren't many xc guys here anymore. I bet those guys would have used them. But general consensus in fr and dh is carbon=death or paralysis :)

My Sugar has Carbon Chainstays. I wonder if putting a brake booster will cause the stays to bend in a way not intended by the designers.

I would not trust a full Carbon frame. They dont like knocks, heat like inside cars, and will eventually fatigue. A bit like Aluminium except for the heat bit.

If money was no object - Ti baby, all the way

I use carbon bars and seatpost on my XC bike. I dont see any reason not to use a carbon frame as long as youre just trail riding. Its just as safe, but if you're going to be doing big, high impact stuff, Id look elsewhere. Carbon is real nice though. I love the stuff. I want some carbon pants.

Hmmm, this is strange, maybe its a different type of Carbon Fiber used, but on Formula one cars the whole chassis is made of Carbon fibre and its incredibly light and incredibly rigid.....

When the guy who designed the first Carbon chassis for a formula 1 car actually showed all the drivers and teams his design, they all thought he was off his rocker, apart from 2 teams or something like that who decided to try it....

Anyway, the cars were much faster, obviously, but when a car hit the wall, they all thought he'd be dead, but the carbon actually kept the guy alive in a 160mph head on crash into the wall with a carbon fibre chassis, and the shear vibrations from the cars when it hits speeds of 200mph when its flying down the straight is probably more violent than hitting a 4 ft drop on a carbon mtb frame, so why dont we trust it if its already a tried and tested technique in cars, seeing as we all know how versitile and strong it is....

Im the same, i dont trust Carbon, but i think its strange why i dont considering this little fact about the cars....

Nevermind eh? :P

The Trek fuel 70... I hear some guys do 5 foot drops with the thing and there are no issues, I hear it is aluminum but I have been told that it is carbon, I hear the frame is very strong and light, any recomendations If you wanted this bike, would you get it?

The problem with CF is that there is no warning when failure is emminent. It's usually explosive and catastrophic.

Plus, minor gouges are enough to damage the integrity of carbon.

I've ridden a lot of different bikes, road and mountain made of CF. Would never buy one.

With that said, I do use a set of Easton's Monkey Lites for my bike. I don't do a whole lotta jumping and the Easton's are stronger than most aluminum bars. I do think that it is to change them (a couple season's old) and will probably stick with aluminum upon replacing them.

I would stay far far away from a carbon seatpost.

Is the trek fuel 70 carbon fiber? I'm confused about this bike If its carbon then Its a nono to buy but if its not then its a yes yes because I like it but I don't want my frame breaking. Didn't buy it yet, just another 30 days

I think it is just the linkage.

Formula One racecars aren't meant to be durable, they're meant to go really fast for a weekend. The frame of an F1 car is not made of CF, just the skin.
Just watching hockey sticks explode by the dozen (last year, of course) was enough to get me to stay away from CF parts for a few years to let them (scienticians, of course) figure out how to make it more durable.

Or, you know, until I develop x-ray vision and can spot any hairline stress fracture in a second.

Before you panic about CF, read THIS (http://www2.sjsu.edu/orgs/asmtms/artcle/articl.htm). It is a little outdated, but educational. At least you will know what are the benefits of various materials and how construction and intended application are key.

Obviously nobody in his/her right mind would use a CF frame for heavy duty riding (downhill, freeride, jumps, etc), but you cannot deny the benefits of CF for certain applications, such as XC riding. While catastrophic failure of CF is a possibility, I doubt that your average XC rider (130-170 lbs) has to be worried about it.

trek fuel 70s are not carbon fiber... full aluminum... i have one and love it. not the lightest thing in the world, but it's not that bad, and I like the bike for the money.

There aren't many xc guys here anymore. I bet those guys would have used them. But general consensus in fr and dh is carbon=death or paralysis :)


Where did all the XC'ers go?

I'm an XC'er... but i know why there arnt many of them... cuz freeride and DH is more fun :)

I'm an XC'er... but i know why there arnt many of them... cuz freeride and DH is more fun :)



LOL...well being a newb to mountain biking I will have to reserve final judgement of that for myself...however for now I would rather ride across 15-20 miles of varied track that just bomb down the same hill all day long.

Where did all the XC'ers go?

Its hard to have a single discussion area for both groups as they are very different. We tend to disagree on most topics like strength and parts needed. There were a few that stuck around a long time but they just kind of stopped coming. Too bad too, for the most part I really liked most of them except the most extreme retro grouches. If we had two seperate areas it might bring some of them back to discussions for xc and for dh/fr and allow us to mix and match topics.

LOL...well being a newb to mountain biking I will have to reserve final judgement of that for myself...however for now I would rather ride across 15-20 miles of varied track that just bomb down the same hill all day long.

:D...you are definately a xc guy. Although, dh is far more than that and there is usually more than one 'hill' and personally I also hike a bike which gives a lot more options than just lift assisted :) To assume dh is not varried...definately find a REAL dh HILL and call it not varried. haha

I cant get myself to trust anything carbon on my bike except maybe a waterbottle cage...I do mostly free ride stuff and ive read about how some peoples carbon bars snap and that scares me shiftless. Maybe in 10 years if they improve carbon (which they likely will) i will go, as for now its more of a beta

Okay. I'll be the oddball here. I'm primarily an XC and trail rider. I ride a full carbon frame. The mainframe is made of two ultrahigh-modulus thermoplastic carbon fibre half-shells each with several intermediate-modulus layers underneath that are bonded together to an internal high-modulus "backbone" structure. The design is a hybrid monocoque with internal structural reinforcement. The swingarm is made of high-modulus thermoplastic bladder molded CF. The fork legs also use the same construction process as the swingarm as does my seatpost and handlebars. Fork legs, swingarms, seatpost and handlebars were produced by Easton under license from K2. The main frame was constructed natively at K2.

The bike has survived multiple crashes... some of them pretty horrific. In one crash, I missed an outside line, got flung down the side of a hill and slid a hundred feet with my bike bouncing along after me. In another accident, I stupidly hit a jump bad and endo'ed with the bike flying over me and tumbling end over end. After every crash, I do a UV test with vasoline and a blacklight and I also keep a record of impedence test points that I measure across with an ohmmeter to detect any problems in the frame. There have been several similar stories of nasty crashes and incidents involving the K2 Oz and ProFlex 4x00C series of bikes. In almost all the cases, the bikes survived fine. One guy on the ProFlex Riders Group forums did discover a crack in his frame and successfully repaired it. It wasn't an easy task but the fact that the CF is thermoplastic vs thermoset makes it possible. Additionally, thermoplastics are generally much better at surviving impacts and have less notch sensitivity than thermosets. The biggest issue with thermoplastic construction is that it's much more difficult to bond to metal parts.

And to also put in some possitives. The one guy I do know riding the carbon frame liked it (at least from reports) and it survived some huge crashes.

http://www.bcdracing.com/

Definately a worthy bike but a little out of most people price ranges :)

Formula One racecars aren't meant to be durable, they're meant to go really fast for a weekend. The frame of an F1 car is not made of CF, just the skin.
Just watching hockey sticks explode by the dozen (last year, of course) was enough to get me to stay away from CF parts for a few years to let them (scienticians, of course) figure out how to make it more durable.

Or, you know, until I develop x-ray vision and can spot any hairline stress fracture in a second.

F1 chassis is made of serveral materials, including carbon fiber. A short copy & paste from F1technical.net




Producing the composites - R24

The right cut
An F1 chassis is not simply composed of one type of material: up to five different types go into producing the finished article, including carbon fibre, resins, and aluminium honeycomb.

" The first step in cutting the carbon fibre is to transfer the digitised files of each part to the Lectra cutting machines" explains Composites Manager Colin Watts. "Once this has happened, the software then collects together all the parts to be produced from a particular material, and organises them as efficiently as possible. One thing we can never change, though, is the orientation of material when it is cut: the fibres must run in a specific direction according to the forces the part is subjected to."

The collection of parts is called a 'marker', and once this is ready, the machine can begin cutting. "For the upper part of the chassis, we cut up to 500 different shapes which must then be laid up in the mould" explains Colin. Cutting all the markers for this part of the chassis takes between two and three hours.

Skins and sandwiches
The chassis itself is composed of three layer: the outer skin, the 'core' and the inner skin, in what is termed a 'sandwich' structure. "The outer skin comprises between 150 and 200 'plies', or cut shapes of carbon fibre" explains Colin.

"We assemble the mould, and then begin 'laying up' the plies according to the drawings from the design office, paying careful attention to the orientation of these pieces. We apply different types of carbon fibre in layers, and the amounts of material vary according to the location on the chassis: certain key areas, such as the engine mounts or the roll hoop, require more material to cope with the forces involved."

During the preparation of the skins, the plies are cooked under pressure in the autoclaves in order to 'de-bulk' them, and squeeze the layers of material together. Once the skin is finished, it is then cured in the autoclave before the core and inner skins are added.

Stiff enough ? Light enough ?
In designing and producing the chassis, designers must constantly balance the conflicting demands of weight and stiffness. The thicker the 'sandwich', the stiffer the chassis, but it is also heavier; a thinner core brings advantages in terms of weight, but will flex more. Controls, though, are strict : "For the sides of the chassis, we must homologate the structure with the FIA" continues Colin.

"We produce a sample of the chassis construction, which is then sent away and tested with an impact equivalent to having the nose of another car hit the chassis."

Once this construction has passed the strength test, it is then fixed for the season.

A ten-man job
During the winter, the composites department works night and day, literally, to produce the chassis. "We have ten dedicated chassis laminators on day- and night-shifts" explains Colin. "We have two upper moulds and two lower moulds in the clean room at any one time, and lay up two chassis simultaneously."

Although the chassis may require the greatest manpower, it is actually an exception to how the composites department usually works. "For almost all other components, a single technician will produce the entire part from start to finish" concludes Colin.

"It is not the most efficient method, but our system is optimised for producing the best quality part. It improves consistency, and also gives the technicians a real pride in their work."

It's the kind of attention to detail that makes the difference in Formula 1.

I xc and I am getting the trek fuel 70 in a few days, now that I know that It isn't cf it is something to get

I xc and I am getting the trek fuel 70 in a few days, now that I know that It isn't cf it is something to get
I don't know if it's right for you. It weighs more than 10 lbs and cost more than $17.