Carbon Fibre-advantages/disadvantages

The only one of those questions that has an answer is the last one. The aerospace industry has placed such a huge demand on carbon fiber production that for the next five years or so it's only going to get more expensive. Everything else is dependent on too many factors to generalize. You'll have to test ride some bikes to find out if the change is worth it for you.

dalysaha said:

I currently have aluminium Avanti Monza triple chain ring, which weighs 22kg with 2 bottle cages and clipless pedals.

Whoa, 22kg??? That's a tank, not a road bike! Are you sure you don't mean pounds, rather than kg? 11kg would be about right for a standard, not tricked-out-for-the-last-gram road bike. If that is what you have, I wouldn't worry too much about the weight right now. If you are in fact at 22kg, my advice would be to get a new frame and fork; these two components are likely to give you the most weight reduction. Note however that you don't have to go carbon to get a bike weighing around 11kg.

I have a trek 1000 made out of AL and a Tarmac Composite. I feel jarred after each ride on the Trek, I feel like I've been shaken in the arms or lowerback area on the Trek. I never get that feeling on the Tarmac, it feels so comfortable. If youre in to comfort, get a carbon bike.

dalysaha said:

What are the advantages and disadvantages of carbon fibre frames?
I currently have aluminium Avanti Monza triple chain ring, which weighs 22kg with 2 bottle cages and clipless pedals. Its a great bike , but I'm thinking of upgrading ( 42 years old , live & ride in hilly area, and knees not getting any
younger! ).

--How would Carbon fibre forks improve an aluminium bike?
--How would carbon fibre seat or chain stays improve an aluminium bike??
--How would carbon fibre seatpost improve a bike???
--Would I only notice a significant improvement from my aluminium bike, if
I bought a bike with carbon fibre frame & fork????
--Would a carbon fibre bike be strong enough for steep descents down bumpy
sealed country roads?????
--Could we expect carbon fibre to become relatively cheaper as it gets
more common??????

Thanks for any unbiased information-- I want to be educated! Dave.

Dietmar said:

Whoa, 22kg??? That's a tank, not a road bike! Are you sure you don't mean pounds, rather than kg? 11kg would be about right for a standard, not tricked-out-for-the-last-gram road bike. If that is what you have, I wouldn't worry too much about the weight right now. If you are in fact at 22kg, my advice would be to get a new frame and fork; these two components are likely to give you the most weight reduction. Note however that you don't have to go carbon to get a bike weighing around 11kg.

Yeh I figured the same 22lb = 10kg.

If you bike is 10kg, probably the max you could save without spending mega$ is about 2kg. I'm 45 and have lost 4kg this year, which was a dam sight cheaper than trading my 10kg bike in on a 6.8 - 8kg one.

Buying a new bike won't necessarily solve the knee issues, the problem could be the riding position, seat too high/low/forward/backward. Could also be the width of the cranks or the amount of float in the cleats.

vchu7105 said:

I have a trek 1000 made out of AL and a Tarmac Composite. I feel jarred after each ride on the Trek, I feel like I've been shaken in the arms or lowerback area on the Trek. I never get that feeling on the Tarmac, it feels so comfortable. If youre in to comfort, get a carbon bike.

I couldn't agree more. I used to ride a 2004 Giant OCR3 and now ride a 2005 Specialized Tarmac Comp. I can tell you that I ride a lot more now that the "hum" has been taken out of the road. I absolutely love my Tarmac.

There are many methods of building with carbon. A bike can be built up with composite tubes and metal lugs, composite lugs or continuous carbon lay-up. They all have their place. I'd look for a bike with carbon stays and post, since that will be easiest on the budget and give you a nice, smooth ride. Almost every maker has a bike or two like that.

I demoed the OCR 3 and thought that was much more comfortable than the trek 1000, almost bought the OCR over the Trek...My guess the AL frame is just uncomfortable. I wonder about those guys spending 2k to get an AL bike, super light but must be real harsh...

rosborn said:

I couldn't agree more. I used to ride a 2004 Giant OCR3 and now ride a 2005 Specialized Tarmac Comp. I can tell you that I ride a lot more now that the "hum" has been taken out of the road. I absolutely love my Tarmac.

benkoostra said:

There are many methods of building with carbon. A bike can be built up with composite tubes and metal lugs, composite lugs or continuous carbon lay-up. They all have their place. I'd look for a bike with carbon stays and post, since that will be easiest on the budget and give you a nice, smooth ride. Almost every maker has a bike or two like that.

Not true. A CF seatpost has no intrinsic properties that make it more comfortable, and the same goes for CF rear triangles. In fact, about the only benefit to CF rear triangles in an otherwise metal frame is cheaper costs for the manufacturer.

You cannot make absolute statements about a component, frame, or bike. You have to consider the design, construction, and use of materials. Full stop.

A common theme I am reading in forums and mags is that carbon fibre forks are more comfortable. How can this be as comfort to me indicates they flex. I thought, by virtue of cf's use in motor racing, that cf would be as stiff or stiffer than aluminium or chrom-moly.

Also, weight savings from cf must be marginal... A trek 1400 alloy with cf forks is the same weight as an all cf avanti carbonio. The bianchi FG lite alloy with cf forks is 800gr lighter than the trek and avanti.

So its obviously $$$ over product. The Baum titanium/cf bike was 6.66kg without pedals... but cost $12,000AUD...

fauxpas said:

A common theme I am reading in forums and mags is that carbon fibre forks are more comfortable. How can this be as comfort to me indicates they flex. I thought, by virtue of cf's use in motor racing, that cf would be as stiff or stiffer than aluminium or chrom-moly.

First the bulk properties of any CF product depend on the fiber, fiber orientation, the lay-up, and so on and on and on. CF products can be flexy or more rigid, and they can be rather flexy in one direction while being stiff in another. For all forks, most flex happens at the fork crown....where the steerer meets the rest of the fork. Given it's flexibility in design and given it's ability to be rather stiff while being lightweight, manufacturers can make CF forks that are as comfy as steel or Al forks.

CF's appeal in motor racing is that it can make lightweight stuff that is still muy strong and stiff, and it can be molded into shapes that can solve other design or performance issues at the same time.

fauxpas said:

Also, weight savings from cf must be marginal... A trek 1400 alloy with cf forks is the same weight as an all cf avanti carbonio. The bianchi FG lite alloy with cf forks is 800gr lighter than the trek and avanti.

Depends on the design, again. The Avanti Carbonio is nowhere near the cutting edge of CF bike design. Go to the edge, and you'll find Parlees, Parlees, Cervelos, new LeMonds, Spins, as well as others that are sub-1000g frames or sub 900g frames.

fauxpas said:

So its obviously $$$ over product. The Baum titanium/cf bike was 6.66kg without pedals... but cost $12,000AUD...

It's obviously nothing of the sort. For your $12,000AUD ($9050 US), you can build a CF framed bike that will easily duck under 6.7kg and approach or better 6kg. At Weight Weenies and RoadBikeReview, one poster--IUBike--built up a Scott CR-1 that weighed 11lbs and change. His CR-1 was an everyday riding bike that he raced, as well. It was no project bike confined to a shop window.

dalysaha said:

What are the advantages and disadvantages of carbon fibre frames?
I currently have aluminium Avanti Monza triple chain ring, which weighs 22kg with 2 bottle cages and clipless pedals. Its a great bike , but I'm thinking of upgrading ( 42 years old , live & ride in hilly area, and knees not getting any
younger! ).

--How would Carbon fibre forks improve an aluminium bike?
--How would carbon fibre seat or chain stays improve an aluminium bike??
--How would carbon fibre seatpost improve a bike???
--Would I only notice a significant improvement from my aluminium bike, if
I bought a bike with carbon fibre frame & fork????
--Would a carbon fibre bike be strong enough for steep descents down bumpy
sealed country roads?????
--Could we expect carbon fibre to become relatively cheaper as it gets
more common??????

Thanks for any unbiased information-- I want to be educated! Dave.

Here's an abbreviated over-view:

Good carbon fiber mimics good steel at a reduced physical weight.

A good carbon fiber fork will provide a better "ride" than an aluminum fork, but not necessarily better "ride" than a good steel fork. If an aluminum road bike has a steel fork, then changing the fork to a carbon fiber fork will reduce the weight of the bike by about a pound, but will not have a significant effect on the ride you experience.

There is such a thing as "bad" carbon fiber (too stiff OR too flexy due to lack of sufficient material); but, you would probably have to buy something (e.g., a fork) that was fabricated a half-dozen years ago ... Kestrel forks have always been one of the best buys, IMO, with a predictable ride.

FAT tires (700x32, or larger) will probably give you a more comfortable "ride" on a harsh road than carbon fiber forks or stays ever could ... if they fit in a bike's frame.

Similarly, 700x28 will give you a better ride than 700x23 ... if they will fit.

A carbon fiber seatpost is mostly cosmetic with SOME weight saving.

A carbon fiber frame IS strong enough to withstand the rigors of a mountain road descent ... as long as you stay ON the road. SOME frames are better than others.

If EVERYTHING on two bikes, as you describe (one aluminum and one carbon fiber) were the same ... exactly the same (same geometry & components) ... then you would indeed notice a differnece with the aluminum frame transmitting more road vibration than the carbon fiber frame.

Some carbon fiber handlebars weigh more than some aluminum handlebars.

Carbon fiber CAN fatigue.

Carbon fiber, like aluminum, can fail catastrophically.

Carbon fiber IS cheaper than it used to be, but the price will always be high with the exotic renderings (e.g., Easton's current nano-tube technology) ...

The bulk of the carbon fiber "stuff" that is out there is currently made in Taiwan ... as long as their currency is tied to the US Dollar, we are all in for lower prices over the course of time.

Apparently, in the past couple of years, great strides have been made in "manipulating" how carbon fiber is fabricated & incorporated in bike frames -- Giant, a Taiwanese company, is said to be amongst the companies on the cutting edge of carbon fiber fabrication.

Dietmar said:

Whoa, 22kg??? That's a tank, not a road bike! Are you sure you don't mean pounds, rather than kg? 11kg would be about right for a standard, not tricked-out-for-the-last-gram road bike. If that is what you have, I wouldn't worry too much about the weight right now. If you are in fact at 22kg, my advice would be to get a new frame and fork; these two components are likely to give you the most weight reduction. Note however that you don't have to go carbon to get a bike weighing around 11kg.

You're right, my aluminium Avanti Monza bike weighs 11kg ( 24 lb ),
NOT 22kg--I was typing in a hurry--22kg WOULD be a tank!!
Thanks for the replies- keep them coming.

alienator said:

Not true. A CF seatpost has no intrinsic properties that make it more comfortable, and the same goes for CF rear triangles. In fact, about the only benefit to CF rear triangles in an otherwise metal frame is cheaper costs for the manufacturer.

You cannot make absolute statements about a component, frame, or bike. You have to consider the design, construction, and use of materials. Full stop.

I absolutely agree. I ride the Cannondale Six-Thirteen. The bike rear triangle is AL. It is the most comfortable ride I have had in over thirty five years of riding. The R 5000 by Cannondale is entirely AL except for the fork which is carbon fiber. I almost bought it. The R5000 is almost as light and rode very nicely. It weights a little over 16 lbs fully built up and on a fifty mile ride it did not seem harsh at all. I enjoy the Six-Thirteen a bit more for cornering, climbing and descents and it is less than 16 lbs with pedals and fully built up. Both frames use Caad 8 AL and the stays can be flexed by a firm squeeze. The Six-Thirteen is a joy on a century ride. Last year I logged in more than 3,500 miles in the summer. I still love it.

Instead of trying to figure out how a bike may ride, you have to try it yourself. In other words ride it, do not think it . Try everything including pure carbon bike designs, combinations, pure metal designs, etc.

alienator said:

For all forks, most flex happens at the fork crown....where the steerer meets the rest of the fork.

Only if it's broken. Forks flex over their entire length, and that has much more to do with the rake than what material it's made out of. With the exception of old heavily raked steel forks, almost everything you hear about flexing parts affecting comfort is a steaming pile of BS. A comfortable bike is not comfortable because it's "vertically compliant" or because the material has some magical "dampening" capabilities. A comfortable ride happens by tuning out high frequency vibrations, and this can be done with absolutely any material.

vascdoc said:

Both frames use Caad 8 AL and the stays can be flexed by a firm squeeze. The Six-Thirteen is a joy on a century ride.

Funny you should mention that. I rode into the office this morning on my '91 R500, and Cannondale has come a long way since then. Back in the day they were just welding up the stiffest oversized tubes they could get their hands on and the bikes ride like jackhammers. They've since realized that for the rear tetrahedron, tube stiffness doesn't have too much influence on structural stiffness. By going to the more flexible stays they've cut weight and buzz without giving up much lateral or torsional stiffness.

alienator said:

Not true. A CF seatpost has no intrinsic properties that make it more comfortable, and the same goes for CF rear triangles. In fact, about the only benefit to CF rear triangles in an otherwise metal frame is cheaper costs for the manufacturer.

You cannot make absolute statements about a component, frame, or bike. You have to consider the design, construction, and use of materials. Full stop.

It's a lot more labor intensive and costly to build a carbon rear triangle than a metal one. If your statement were true, then Huffys would be made of carbon.

Don't make a warning about absolute statements and then make one.

benkoostra said:

It's a lot more labor intensive and costly to build a carbon rear triangle than a metal one. If your statement were true, then Huffys would be made of carbon.

Don't make a warning about absolute statements and then make one.

A metal rear triangle requires the two seat stays to be compound mitered differently for each size frame, and there are six welds (two top, two bottom, and two for the bridge). With a carbon wishbone monostay, only one tube gets welded on (simple miter), and the wishbone gets cut to length and glued to the frame/dropouts. Same deal with chain stays. There's absolutely no question that this takes less time than using metal tubes.

artmichalek said:

Only if it's broken. Forks flex over their entire length, and that has much more to do with the rake than what material it's made out of. With the exception of old heavily raked steel forks, almost everything you hear about flexing parts affecting comfort is a steaming pile of BS. A comfortable bike is not comfortable because it's "vertically compliant" or because the material has some magical "dampening" capabilities. A comfortable ride happens by tuning out high frequency vibrations, and this can be done with absolutely any material.

Fork crown AND steerer...I forgot to type steerer. Still, both the crown and the steerer flex more than the legs.

As for the damping, tuning, or flexing, I guess you'll have to ask the bike designers and engineers what they're doing, won't ya? You have to really wonder if they're studying the frames or parts to see what shapes, lengths, and whatever else will extinguish certain modes. And then you have to wonder exactly what modes they're going to allow to exist. Tuning and damping are different means to achieve the same end. As for flex......with respect to a frame, vertically, it's insignificant, granted. But for a fork, it's not an insignificant value.

alienator said:

Fork crown AND steerer...I forgot to type steerer. Still, both the crown and the steerer flex more than the legs.

As for the damping, tuning, or flexing, I guess you'll have to ask the bike designers and engineers what they're doing, won't ya? You have to really wonder if they're studying the frames or parts to see what shapes, lengths, and whatever else will extinguish certain modes. And then you have to wonder exactly what modes they're going to allow to exist. Tuning and damping are different means to achieve the same end. As for flex......with respect to a frame, vertically, it's insignificant, granted. But for a fork, it's not an insignificant value.

If the steerer on your fork is flexing, there's a problem with the headset. And while it may see the highest bending moments, the crown is orders of magnitude siffer than the legs. As for vibrational characteristics, it's a lot easier than you think to tune a frame. It sounds like you're confusing oscillations of the entire frame with oscillations of the individual tubes. It's not about selectively extinguishing certain mode shapes,(whatever that's supposed to mean) but simply picking out a tube set that's going to transmit energy at the lowest possible frequency. For the record, I am an engineer, and I have designed tube structures with dynamic constraints. It's not brain surgery.