Differences in Carbon Quality

Not just the carbon but the resin matrix used, some sheets of carbon come pre injected with resins which make the assembly easier and more cost affective. I believe Giant mixes their own resins which gives them more complete control over the process

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If you just want it to FEEL faster, buy a super stiff frame and use narrow tires with tubes. There are tons of examples out there of reviewers saying something FELT faster, but performed slower.

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That is the correct definition of durability, but it’s also assumed that durability lies within the scope of intended usage for a given product. You don’t judge a TV screen’s durability by it’s ability to withstand wear, pressure, and damage when it’s used as a tabletop. You don’t judge a torque wrench’s durability by it’s ability to be used as a prybar.

Carbon bikes, of all grades, are phenomenally durable when used as bikes and ridden. When talking about how they survive being struck other sharp edges that isn’t a reasonable frame within which to judge the durability for a bicycle… but, even then, as evidenced from the video I posted earlier in which they’re literally smashing a high modulus carbon fiber bike into a concrete pillar without it suffering catastrophic damage, bikes made from high mod carbon are still incredibly durable.

So… to the original point, durability isn’t a measure of how much of a beating a thing can take. It’s a measure of how well it performs it’s intended function without wearing out or becoming damaged.

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I can’t remember which nerd alert podcast this was on. I think that the raw carbon fiber is offered in 4 grades, ranging from lowest to highest modulus. I think I recall that higher modulus is stiffer but more brittle.

When we get to the frames, remember that they’re made up from a bunch of cut up bits of prepreg carbon. I think that frames vary in the mix of lower and higher modulus CF sheets that go in to the layup schedule. So, it’s not a high modulus CF frame, it just has more of the higher modulus bits than the next tier. Also, I think the higher tier frames may use a more complex layup schedule, E.g. more smaller pieces to save weight or improve other characteristics.

I think that the CT gang may have reviewed the S-Works and regular Aethos, so that would be one data point.

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This is, mostly, spot on… It’s not always prepreg but, otherwise, this is essentially true.

So, for starters just to cover the basics, carbon strands have a certain modulus depending upon how refined they are… this thins the strand out but leaves a strand that, by weight and volume is much stiffer than a less refined strand. Since it’s been thinned out though, it’s more susceptible to snapping when subjected to stress than a thicker strand would be. A key thing here as well is that there’s no universal standard for what constitutes a “high modulus” that translates across all manufacturers so when two bike companies both say they’re using “intermediate modulus” fiber, there’s no way to know that they’re both using the same fibers. Unless they specify the actual material they use, say T800S, you can’t really do an apples to apples comparison.

Those strands are then woven or bunched together into a tow… the number of filaments in a tow is where the “k” value we’re all accustomed to hearing comes from, 6000 filaments per tow is a 6k tow. The thinner the strand, the more strands of filament that can be combined in a tow… so there’s more fibers, which are each individually stiffer, combined into a tow vs a lower grade of carbon but, since they’re lighter, the weight by volume remains lower.

So, when they start building frames they have target metrics for various strength and stiffness values as well as tube shapes and such. Then they take the material properties of a mid grade carbon and figure out how much they need to put and where to put and in which direction to achieve those targets. For a high end, high mod frame, all they do is swap out the material properties with the higher modulus tows’ values and figure out where they can change the layup schedule of how much/where/what direction to still achieve those target values.

To the original question… You will occasionally end up with a bike that has a bit different ride characteristic than the lower mod frame since there will be areas where they needed to add more higher modulus to meet strength targets than would’ve been needed just to meet the stiffness target so the high mod adds to the stiffness beyond the original target that was met on the low mod frame… but as more and more companies have refined their processes and the computers doing the calculations have gotten better, they run more variations and get closer to target now than they used to so it’s become less frequent that a low mod and high mod version of the same frames ride substantially differently.

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This is timely. I had the misfortune* to come off at some speed 2 days ago. I am pretty bashed up (though thankfully nothing that won’t heal fairly quickly).

There is not a mark on my Factor frameset - not a mark.

The last time I did the same I was on a CAAD - and it was a write off.

*that’s inaccurate. It was total ineptitude.

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Heal fast and well!

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Just to confuse things further, there are more factors at play than weight and carbon stiffness.
There’s not much discussion for example about the response of the frame to vibration. In general a lighter, stiffer frame containing more material will resonate at a higher frequency than one which is heavier or contains more material. This may be perceived as being ‘tighter’ or ‘lively’ or alternatively ‘harsh’ with the heavier frame being ‘dull’ or ‘lifeless’ but possibly ‘composed’. This would be true even if for example static bottom bracket stiffness were equal on the frames in question.
So for a race bike stiffer and lighter might align more with the perception of how a race bike should be. For an endurance bike a bit more material might align with the composed expectation of how a bike of that type should behave.
TLDR if you’re not racing the frame you want is titanium :grinning:

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Personally, this feels like one of the biggest marketing and product positioning scams in the bike industry. Even Specialized now says that an S-Works SL7 and a regular SL7 should feel the same. The only difference is the weight and the paint job for a $2200 difference in price. I honestly wouldn’t put it past bike manufactuers to leave an extra 200 grams of resin in the lower spec frames to up the weight.

CT did a podcast. I think it was Ruckus, the carbon repair outfit. They basically said that they could see very little difference between the high spec and low spec frames. It was kind of a wink, wink comment as they didn’t seem to want to fully rat out the industry.

Maybe this one:

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Thanks, that is an interesting podcast. Interesting that Raoul talks a lot about the durability of light frames and how it may desirable to add weight.

It is interesting that in the UK Specialized only make their high end S Works frames available to buy as framesets. Guess they just make so much more money on them.

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Haven’t listened to the podcast but, if they actually said that, than the only thing they ratted out was their own incompetence. There’s a very noticeable difference.

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If you ever buy a TCR and actually read the manual they say they these bikes are ‘not a workhorse’ (that may not be the exact phrase, but it’s very close) and that their durability and robustness is reduced in the quest for higher performance. While I’m not aware of any TCR failures (in fact, Giant seem to be pretty reliable, admittedly from anecdote), that’s an interesting admission.

Having said that, any material can, and does, fail, and I remain convinced that manufacturing quality is the single biggest determiner of durability. My father was a structural engineer and briefly talked to him about this issue. His reply was that while he knows very little about CF, it would be the same principles as everything else: design it properly, deciding how much safety/durability margin you want or need to build in, make it well (ideally building to a spec not a price), and invest in decent qc. He imagined it would be pretty straightforward to build a CF bike frame that would survive anything bar a spectacular collision/car crash, but it would weigh the same as a steel one

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This is sort of true… their manual does say that but it’s not in reference to strength differences between high and low modulus carbon frames, or on the TCR specifically, it applies to all their “high performance road” bikes. So it even applies to something like the alloy Contend.
giant

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At least that is honest and stated in human language.

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It was so easy when it was…

Columbus
Cromor
SL
SLX
TSX
MS
MAX
SP

Reynolds
501
531
631
653
753
853
953

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But it never was actually that easy. The introduction of 953 was in 2012, by which time carbon had been the dominant material in high end bike frames for close to 30 years.

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I read the post as being satirical, but I could be wrong…

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You’re probably right, it’s so easy to be tone deaf on the intertubes.

It was easy choosing Columbus (SL, SLX, TSX & MAX)…Reynolds started to make it a bit confusing, initially it was 531, 653 and 753.

Try confirming the grades of carbon being used today between manufacturers on low to high end frames!

I see it was me being tone deaf! :slight_smile: