PeteHski

It would be more useful to know the actual frame weights in regard to their likely fragility. I have to say their marketing blurb is of the highest order bs. So that would make me question their credibility.

PeteHski

It didn’t go well for this 185 lb rider. Frame cracked within 6 months and warranty refused because he was 5 lb over limit. But their previous marketing strategy was more interesting 🤨

https://forum.cyclingnews.com/thread...-decide.33173/

SoSmellyAir

sir_crash_alot Going by the recent posts you started, including this one, it seems you are in the market for a road frame. Perhaps consider here: Road Frames for Sale | BikeExchange.com

I am not affiliated with BikeExchange (or any other bike company).

sir_crash_alot

I am indeed in the market for a road frame. Or at least I was...I might have stumbled into good upgrade from my current bike instead. Regardless, as a noob and sports gear tech-nerd, it's been helpful and interesting to do this research and ask questions of the community so I have an idea of what to look out for as I'm getting started.

Thank you for the resource! I will poke around that site.

Jughed

I've heard some sprinters claim that their bikes are spent after one grand tour. They claim that they can feel the difference in the frame...

After watching the stage 4 sprint yesterday, seeing the bars and front ends flex under the power of these riders (and seeing completely assploded crashed bikes) I can see how they can wear a bike out.

As a 190# rider with reasonable peak power - nothing lightweight for me!!

PeteHski

We used to get similar claims from F1 drivers about their carbon chassis losing stiffness after half a season of racing. Having torsion tested numerous chassis, there was never any evidence to back up those claims. It was just a mind game to rationalise defeat. Funnily enough they rarely complain when winning. I expect it’s the same with pro bike racers.

A carbon structure will basically maintain its strength indefinitely unless physically damaged. Which can of course happen with even relatively minor accidents. I’ve also seen carbon frames snap at the point where they had been clamped on the team car roof. There was a thread here a few years ago about a Ridley frame that had broken like this. It had broken while riding along about half way up the seat tube with no obvious stress point. Someone then posted a photo of the bikes clamped on roof racks in exactly the same place where it broke.

Jughed

What if the structure is so lightweight/lightly built that it gets physically damaged from "normal" use? By "normal", I mean a 1800w++ pro rider putting the structure thru its paces over the course of a grand tour, or series of grand tours - where they exceed or come close to the max the design capabilities of said structure?

The claims I heard them make was that frames felt "dead" by the end of the tour. Is it not possible that the stresses they put the frames under cause micro damage that changes the characteristics of the structure?

sir_crash_alot

My original sport is ice hockey, and this absolutely happens to our carbon fiber sticks. While most of them break after a month or two of heavy use at higher levels (if not sooner), if they survive, they lose their "kick" or "whip". They flex under load, but don't spring back as a fresh stick would. As a smaller player who didn't load sticks as much during my career, I seldom broke carbon sticks, but I did end up with a pile of "spent" sticks sitting in my garage, haha.

Edit: On that note, hockey players who "know" will tell you the performance differences in terms of kick between the mid-grade and upper-end sticks is minimal, the difference is weight-savings, as top end sticks are feather-light. Interestingly, the prevailing wisdom is that if you want a stick for pure performance (weight+kick) you get top end, but if you want a durable stick with kick, go mid-grade.

Carbonfiberboy 

Here ya go: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6829243/
and
https://www.limit-fatigue.com/limit-...-life-fatigue/
and
https://iopscience.iop.org/article/1...8/1/012017/pdf

I was under the impression that CF had no known fatigue limit, but that's because I was dealing with overbuilt structures which were designed for minimal flex. One assumes that quality CF bike frame manufacturers put strain gauges on their test frames when they hand them over to the test riders, so they're not just going by feel. The idea is that a good CF bike frame doesn't flex in such a way as to absorb power from the rider. When I got my CF frame in 2000, I noticed a huge difference in my ability to accelerate it compared with the 80s steel frames I had been riding, which felt like I could rip the bars off in a sprint. Otherwise known as stiffness. I would assume that a CF frame optimized for weight rather than stiffness would have a shorter service life. Obviously, pros look for a balance there. BTW, steel frames have a shorter fatigue life than CF if stressed similarly.

sir_crash_alot

Fascinating stuff. It's interesting to think about this research and information from a non-pro perspective, where most of us likely aren't putting the kind of stress on a weight-optimized frame that a pro would, and in theory could extend the life of a CF frame longer. At the same time, perhaps even under normal person loads a lightweight frame would still degrade faster than a more overbuilt structure.

Carbonfiberboy 

I'm still riding that 2000 Trek frame. i was the first in our group to buy carbon rather than custom steel. I bought that particular bike because it's the same frame, though a different size, as the frame LA won his first Tour on. But being an early frame, I'd guess it's overbuilt. The bike weighs 18.5 lbs. complete w/o bottles, gear, etc., though some of that is in the old components. Anyway, I've ridden it as hard as I could for a lot of miles. No detectable difference in performance as far as I can tell, but that's what I'd expect from the above papers.

An aside . . . research says that the catastrophic implosion of the Titan took .01 seconds or less, IOW as it is said, they never knew what hit them. They did not experience the collapse. I think the above papers shed some light on that disaster especially the discussion of single broken carbon fibers.

PeteHski

With the UCI min weight of 6.8 kg there is no incentive to design a frame close to the stress limits in normal use. Especially a chunky modem aero frame. Problems only arise when you use a cheap, poorly designed composite layup, badly manufactured with loads of voids etc.

1800W sounds like a lot, but in engineering terms it’s not a big challenge.

Specialized used the Aethos as a showcase for how light you can safely go in a well designed frame without imposing low rider weight limits. 585g frame and 270g forks. The S-works Tarmac is around 800g so very unlikely to be compromised in terms of stiffness.

Don’t the riders feel “dead” by the end of a GT? It sounds highly subjective to me. Have pro teams got to the point of regularly testing their bikes yet like we routinely do in F1? That I don’t know. But I suspect the frames can easily go the distance without measurable degradation if not crashed or abused.

Jughed

Great insight guys… I’m a controls engineer, materials are not my thing.

So if I understand y’all, there is really no degradation and only one failure mode - complete failure.

PeteHski

That’s pretty much correct for a properly engineered, quality carbon frame. People sometimes talk about resin degradation, but I haven’t seen any evidence of it in other carbon applications and certainly not within a year or two. Maybe 30 years.

Most carbon failures are from manufacturing defects, crash damage or other abuse such as over-clamping tubes on bike racks.