I want to start an intelligent conversation about the benefits and downsides to 100% carbon frame & fork configurations vs configurations that use aluminum or titanium in most of the frame but have some areas that are carbon.
In one corner, we have bikes where the frame & fork are all carbon fiber. These fall into two categories: bikes made with a monocoque construction and bikes with carbon tubes and lugs. A common feature of these bikes is that the engineers vary the tube diameters and the thickness of the carbon throughout the bike in order to get the material properties they’re looking for. Examples are Guru’s Chrono, Argon18’s Gallium, Felt F1C, Calfee Dragonfly, Kuota Kaliber, etc.
In the other corner are bikes made with multiple materials, but which incorporate carbon-fiber in strategic places. This year, the trend seems to be to use CF in the seatstays and the fork, but use Ti or Al in the “middle” of the frame and in the chainstay. Some bikes use CF lugs. Examples are the Felt F60, Guru’s Aero’Ti & Tantrik, Argon18’s Mercury, Yaqui Carbo, Serotta Ottrott, etc. (OK, maybe it’s not fair to include the Ottrott.)
I’d like to hear opinions and actual experiences riding each of these designs. The argument from one of my customers who is in the mixed-materials camp is that those bikes have a rigid “middle”, but the carbon seatstay, fork, & seatpost act ask shock absorbers at the end of the bike, so the rigid middle gets plenty of damping at the ends. Another of my customers who is in the carbon monocoque camp says that if you get a good bike, the engineers have designed the middle tubes to balance rigidity and vibration damping perfectly throughout the frames. His argument is you don’t need different materials to get different properties, you just need smart engineers who know how to manipulate carbon.
Anybody want to weigh in?
Lee Silverman
JackRabbit Sports
Park Slope, Brooklyn
I think both of your customers are right. If the designer knows what he or she is doing you can make a great bike out of one, two or hell three or more different materials. Granted CF is tunable as far as ply layup to give different behavior in response to stresses in different directions whereas metals have pretty fixed homogenous material properties. This pushes the arguement a little in favor of CF type constructions. But then again a good designer can do a lot with frame design, tube shaping, tube thickness, s-bend seatstays, etc., etc. This can be done with both CF and metals although I think that in the terms of maturity of design metals have a head up on CF technology simply as metal working has been around longer.
Hybrid CF/metal frames do seem to work very well although they usually don’t seem to offer much of an upgrade in performance over traditional metal frames. Then you have the glued joint problem, but that is rarely an issue if done right.
IMHO I’d give CF the edge mainly in pushing the envelope in frame design as far as far as straying from the double diamond design. CF will give more flexibility in terms of shaping for aerodynamics and possibly for getting the best combination of frame stiffness and comfort. But then again, frames are already under the 2lb mark, aren’t hurting comfort wise and with the UCI restrictions on frame design how much more innovation can we get. Basically we’ll improve aerodynamics and appearance. Weight won’t drop much more and I doubt performance as far as stiffness and comfort can really be improved much at this point.
I believe that carbon seat stays on an otherwise titanium bike is purely marketing hype. Forces from the rear hub are transmitted longitudinaly into the seat stays. The more material they use to make the seat stay, the stiffer it becomes, and the more force transmitted into your seat. This is true of any material type, so it doesn’t matter what it is made of (except in terms of weight).
If I relate this to archery, arrows are made of aluminum primarily but sometimes other materials. But the aluminum arrows come in all sorts of different diameters and wall thickness (mostly made by Easton by the way), which is to create enough stiffness for the draw weight of the bow without being too heavy. The point being that they can make any stiffness or weight they want by varying the properties of the tube.
The seatstays on a bicycle deflect very little anyway…the large bumps are nearly fully transferred, the small vibrations are absorbed by your seat or the lack of a fixed coupling between your seat and butt.
Take a titanium tube, hold one end of it against your crotch and hit the other end with a hammer. Now repeat with a carbon tube. You will notice that the carbon tube hurts much less - this is because you were in so much pain after the titanium tube that you are now either numb or unconcious.
I just purchased a Lemond OCLV/steel frame to replace my aluminium TCR road bike. Lemond also makes an indentical titanium/carbon model.
What impresses me about these bikes is the the steel or titanium parts of the bike is in the right area - the spine of the bike. In the case of the carbon/steel frame it feels like a steel ride but the carbon seat post and top tube lighten the frame up a bit. The thing rides as smooth as butter compared to the aluminium TCR.
Perhaps I’m wrong, but I still have reservations about full carbon bikes . All it takes is one good scrape/gash and you’re got a potential fatigue problem.
Well, as a sufferer of OA in my right hip, my body is quite sensitive to frame material/compliance properties. I can not use a stiff aluminum frame without it aggravating my injury. Carbon fibre, specifically, Trek’s OCLV helps but I still need a flexy seat post (like Specialized Pave) so that I can tolerate 200km (124mi) rides well. As already mentioned it isn’t as simple as frame material alone it depends on the way it is designed. Cannondale designed curved seat stays to provide more compliance (but I don’t think it made that much difference).
Anyway having ridden all aluminium, all carbon and aluminium with carbon forks and seat stays, I can tell you the last 2 ride a lot more smoothly than just aluminium. Out of the last 2 I couldn’t really tell any difference, but my wallet could. And that is the reason for mixed alu/carbon frames, they are cheaper than all carbon to make.
Take a titanium tube, hold one end of it against your crotch and hit the other end with a hammer. Now repeat with a carbon tube. You will notice that the carbon tube hurts much less - this is because you were in so much pain after the titanium tube that you are now either numb or unconcious.
You’re right. And my voice is now 2 octaves higher.
I opted for carbon seat stays on my Yaqui Ocotillo because Ves said it was stiffer that way. I didn’t do any independent testing, research, or whatnot - I just trust the guy.
I am extremely happy with the way it rides, but unless I got another bike built up in an identical manner save the seat stays, I’ll never be able to “prove” anything. And even then, I’d never prove anything to the “scientific, statistically significant, double blind crew”.
