Carbon Fibre Composite

As frame material, or even now everywhere, it seems to be the gold standard.
I really like it as saddle material actually, making very comfortably flexing rails, at a very low weight – still, for insane prices. But in percentage, a lot of weight can be saved here, and comfort to be had. Tune Skyracer weighs 63 grams. A Fizik Arione between 147 and 243 grams.
Same with seat posts. Comfortably flexy and light. Torque wrench NEEDED to install on the bike, though.

My cyclocross frame in 54 cm weighs 1150 grams without fork.
Of course, especially with the advent of disc brakes for road bikes, those frames for road racing bikes have again been drastically reduced in weight, coming in at around 700 grams per frame.
I would not touch any of those, because as with any material, I believe in redundance. Some extra stability, that I might need, when a defect in craftsmanship unintentionally introduced a stress maximum within the layup. So, with a cyclocross frame, an avid amateur like me has the best of both worlds, as I am sure.

Now, let’s compare that 54 cm carbon fibre composite frame to the very same size, make, and geometry in aluminium. The latter weighs in at 1510 grams. That is 360 grams more than CF, if my calculator does not cheat me.

Taking into account that the composite material is perfectly made for the stress its parts are intended to withstand, but, for example, a lot of manufactures will VOID any warranty if the user sits on the top tube (you read that right), for 360 grams more I will gladly take the aluminium version.
It costs way less. Way.
The bottom bracket shell in aluminium or steel frames is usually thread-in BSA standart, with hardly any problems with spec, and other measurements, ever.
Carbon frames are known to have their press fit openings out of specification for the bottom brackets to be pressed in (it is quite a challenge to make a perfectly round shape to the 20th of a mm, when the item in question consists of multiple layers of carbon fibre lay-up, drenched in resin, baked at around 130 degrees Centigrade, and then cooling off back down to room temperature – go figure), causing all sorts of noises from misaligned bearings, and wear of crank arms, loss of watts transferred.
Is it possible to make a perfectly round and aligned BB-Shell from Carbon fibre to mett specifications? Absolutely. But it seems manufacturers (yes, even “brand, expensive ones”) are either too lazy or too cheap. If only their frames were, then, too….

Aluminium can fail as well, of course. But a kick into the side of a tube, a tumble and fall, will usually show a scar on the outside, if problematic.
Carbon fibre can actually deflect and tear on the inside and thus lose strength, with little to no sign of that problem on the outside.

So, only for the very brave, going for a 700grams CFC frame (then with rim brakes of course, for the ultimate in light weight bike), this seems to be a tolerable trade in for stability, and safety redundance.

And for those believing that CFC frames ride better, because they are somehow super stiff, while being somehow super “compliant” at the same time (i.e. cushiony against road bumps) should really curb their intake of marketing outlets, and talk to some engineers about the rigidity of trusses…
If you want cushion, get a frame with a sloping top tube, and sort out the (then longer) seat post most fitting your needs. Get wider tires. Get Carbon Fibre saddle rails, or a saddle entirely made of CFC.
Go blind-compare two identical bikes with identical parts and identical weight (I dare you), one in CFC, one in steel or aluminium, and tell me what you felt.
Which one was “better”? Which one was which material?
And if you did not get around to do this test yet, please shut up until you did.
After that, I am more than willing to learn about whatever you found out.

As for forks, the weight penalty of using anything other than Carbon Fibre Composite is higher in relation to total weight. My cyclocross forks are CFC from drop-out to top of the steerer, being “heavy” at 470 grams, cut to length (around 490 frams uncut).
My Titanium forks weigh in around 800 grams for the same structural stability, aluminium and steel will be slightly heavier still. A skinny road bike fork in CFC can be light as 340 grams.

So, I will cut CFC steerers very carefully with fresh, clean blades, round out the ends to perfection to avoid stress maximums there.
And place a very long expander to go deep inside the steerer tube, and adjust everything to torque specs with a calibrated wrench.
I will use a super sized cone ring for the bearing play adjustment, to reduce stress on the carbon being pressed from the outside, from the inside of the top bearing seat.
I will use stems with at least 40mm clamping height to distribute the forces over as much carbon steerer tube as possible, and will never clamp the top of the tube, leaving at least 1mm exposed, spacer on top.
I will watch that nothing hits my fork legs from the side, ever. And have it inspected if it happens.
I will check for play in the steerer regularly, and also drop out the fork every 4000 km, to check for visible damage where it is clamped and touched by parts of the bearings and stem.

Lastly, I want to point out that my favourite shape drop bars are aluminium, weighing in at 263 grams in size 400mm. The same brand offers carbon fibre bars, same model, triple the price, weighing in at 230 grams. Thirty-three grams saved – One fall-over accident of the bike leaning awkwardly, and you might be in for a surprise later, just riding along.

Find out what is what, and what you need. Do not believe any hype.