Bigger tyres inherently create more rolling resistance. The reason they can perform better in the real world is because they are the only real source of damping on the bike and because they enable safe use of lower pressures. But as long as you can stay in the operaring window of the narrower tyre, it will perform better than a wider tyre for the same percieved comfort/casing tension. And also it'll be aerodynamically faster and less affected by crosswinds.

Frame flex doesn't measurably affect power transfer, only effect it has is mental and on handling. Too much stiffness, does however worsen the damping ability of the system, slowing you down on rough surfaces, and creates more physical and mental fatigue.

I had a really long post written about why this isn't quite right but I realized that no one really wants to debate tire pressure on here. The summary is that if you approximate by % drop the RR should be the roughly the same, but there is a point above which increasing tire pressure increases RR. This is because a tire is not an ideal spring but follows an S curve, and you can end up with resonance / "impedance" mismatch. Wider tires have greater volume and are a lower pressure for the same % drop--meaning you can often run less % drop and still avoid the "impedance" mismatch condition. This theoretically means a wider tire can be less RR, depending on the surface.

Skin tension is related but is a red herring because it's a derivative (in the math sense) of the volume equation that governs the spring rate of the tire.

Given we are talking about resonance and energy absorption, speed is a key input too. The faster you ride, the greater the chance that, on a rough road, you will enter the zone where a higher pressure results in increased RR.

The same resonance / "impedance" issues should also apply to frames. Still, I don't think anyone has published data to suggest when / where a frame is so stiff this actually happens vs. tires when assuming the frame is totally rigid, so we have no idea if this frame or any other is too stiff other than how it feels to the riders.

Just been lookimg myself at this. And emailed Carbonda about RAW black on gloss, said they only had it in blue and sent photo which has the Vitus decals 

So anyone have one?

This isn't surprising. It was pretty well known that Flybike was the OEM for these frames, and after Vitus was cast aside in bankruptcy, these frames were on clearance everywhere. These molds seem to return to Flybike and then are sold via Carbonda after small brands either fold or new models are launched. The strange thing is that Vitus is back up and running now, so...are they still using Flybike, or did they agree to let the molds become open / stop paying for exclusivity?

I don't have one, but I did work with a team sponsored by Vitus that lost its bikes during the bankruptcy and switched to Emonda ALRs. Their riders, even their crit-focused guys, seemed to prefer the Emonda by a wide margin. I didn't inquire too much, but most riders found the bike to be a bit on the stiffer side. On the plus side, as a bike designed for the house brand of what was then the largest bike retailer in the world, the bike worked well with components of the team's other sponsors.

I have a wheelset from a company called DFS. They also claim to be a factory and share a lot of the same molds and model numbers (and have access to more) vs. what carbon bike kit offers.

At the time I ordered, the T1000 layup wasn't available. My front rim is GR50-31A (hooked), and compared to the LB WR50 rims I also have, they are cleaner and visually very well made. Mine are finished UD raw, and there is nothing to hide, no flaws that even concerned me a little. One key difference from some other rims is that tubeless tires do not drop into the center channel when deflated because of a beadlock that is part of the design. Given I ride tubeless, this is a huge convenience if I get a flat or I let them go flat because I have been busy riding a different bike, as they are much easier to plug and reinflate.

My rear wheel is built around a 23mm internal, 60mm deep UV profile rear rim that is not listed by carbon bike kits.

Probably repeating what everyone has said, but a 24mm spindle—especially in a BSA bottom bracket—means larger bearings, which naturally last longer.

I have a DUB Cybrei on my SL8, and since I have a press, swapping it is no big deal. Longevity isn't a major concern for me, but I do use steel bearings (SKF/NTN). I previously had a THM Clavicula with their ceramic bottom bracket, and it was terrible—bearings didn’t last, and as a heavier rider, it was noisy as hell when climbing out of the saddle. That was super annoying since I need everything to be completely silent. I ended up selling it and went back to my Dura-Ace crank before getting the Cybrei.

I’m currently running 54/38 MetAero Cybrei rings with an 11-34 cassette, paired with an X-Cadey power meter, which works fine. I’ll be testing this setup in Gran Canaria next week ahead of Mallorca 312 in April. We’ll see if my legs blow up—if they do, I might switch to 52/36 rings.

The bearings typically used for 30mm/29mm/Dub (6806 or 6806-29) and 25mm/24mm (6805 or MR2537) have the same size balls. BB86 is the only standard where you should want a 24mm axle.

[...] titanium manufacturer Laget is one to watch. They're producing beautiful 3D printed ti framesets with seamless joints and no welds. One road bike I saw came in at 7.4kg and that's titanium!

Laget or TSB is one of the coolest 3d printing companies in bike space IMO. I suspect that most of their work is B2B--and in that sense, they feel like the Silca of China. Their principal is relatively well published in terms of 3d printing metallurgy as well. Not sure how much bike experience they have, but they were at Sea Otter and looks like their staff did the sportive / event there too.

Exact. Except 150g weight difference even up a 2h climb results in a rounding error. Your body weight will fluctuate more than that over such a climb.

You are right; aero is the most important, but it's the aero of the system, not the bike, that matters.

I fall in the camp of folks who think that frame aerodynamics have had more importance attached to them than there should be because people have started to think of them as "free speed." But, if you wind that back and look at CDA numbers and testing protocols you start to see a lot of inconsistency that suggests that aero shaping of a frame has a lot less effect in real world racing than working out the right position or even using a dual layer skinsuit vs. a traditional skinsuit.

A frame like this one probably has a relatively low A in terms of CDA, but more importantly, that extra length, 75-degree seatpost, and low stack allow for the rider to achieve a really low A as well. The round post even opens up the option of using a forward offset post. For the riders that find an improvement from those fit attributes, the change is likely a few multiples more than what an aero frameset with a more traditional geometry would allow when in that fast attack position. A bike that's faster when attacking might be a better fit for riders than one that is optimized for riding efficiently in the flats, depending on the rider's goals. If you were working towards the fastest setup you could get, even within a generous budget, you might be better off getting a frame like this that is easy / cheap to tinker with and spending the money on high-end or even custom skinsuits.

Overall I love the idea of this frame. The geo is unique even compared to the higher-end Chinese and western brands. The only weird thing about this frame is the 43mm offset fork. With this geometry, I would have expected them to use a 47mm.

The ask was for a race-oriented frame first--the inclusion of other use cases was second. IDK, I just think that bikepacking races are an extreme edge case.

Probably not your target market since I already have the bike I want--but building a gravel race frame is tricky because there are so many different kinds of gravel race courses. I think the ideal bike for the old SBT GRVL Black course would have been something like a Specialized Crux, but for a not-muddy Unbound 200 it would be something like the BMC Kaius. From experience in those events, the challenge is focusing the design on the use case that matters. IMO, there are fewer bikes made for the 200+ mile type race event, though that is starting to change. On the other side, it's harder to sell a bike designed for a use case built around an event; only a fraction of people will try and attempt, and only half will finish.

If it were me, I would still pattern the bike after the BMC Kaius in terms of non-custom geometries. To me, a gravel bike focused on racers means:

1. Long reach--about 10mm-20mm longer than bikes like the Specialized Crux. This is needed for FC length as well as toe clearance, but the measure of a good gravel race bike is how well it can take going 40mph on a descent and needing to change lines mid-corner on a loose surface.
2. Tire clearance for 700c x 55mm (29x2.1" MTB) and if possible 650b x 60mm+ (27.5x2.4"). I expect 700c x 50mm to be a widespread size i see at events going forward, so a little wider for those that want it
3. Low BB: Given the wide tire preference, I would consider an 85mm or even 90mm BB drop to really design the bike's handling around a 700c x 50mm tire. This is a big change from many current designs that are designed around a 700c x 35mm or 40mm tire size.
4. UDH
5. I don't think 2x should be an important part of the design. I am currently a 2x rider, but designing for 2x would likely conflict with the tire clearance, which will likely be a more significant consideration and differentiator going forward. I would think of 2x as an option at most, but I would design the bike with the intent of 1x. I would also consider shipping the frame with a chain catcher for 1x rather than a cover if you are making a frame with bosses for an FD mount.
5. Aero frame shapes don't seem to matter as much as aero position on the bike, so I would focus on stem compatibility and consider the integrated bars to be similar dimensions to what BMC offers for the Kaius. Also, people are going to be riding these with pumps, bags, and tools strapped to the bike, as well as a number plate likely in front, so even optimizing for bottles is unlikely to matter when you load it up for racing. Mud clearance is also important, so aero features that require the frame to hug the wheel will probably not work well. Don't be 3T.
6. Avoid the deep aero fork. I really like the feel of the Enve and Open gravel forks, and I would be hesitant to build too stiff a front end on a gravel bike.
7. Mounts: 2 bottles in the frame, one under the DT. Top tube bag bolts. No more. No dynamo wiring. No internal storage. You cant use that in a race and it just adds complexity, weight, and something else that will rattle. Just stick to the essentials.
8. FSA or Deda headsets. I would also use genuine ones or source high-quality stainless bearings because this is a problem area for gravel bikes.
9. Round 27.2mm seat post. Just don't bother with D-shaped. If you race it on gravel, you will break stuff, including saddles and seat post-mounting hardware, so avoiding proprietary parts is essential.
10. Don't bother with comfort gimmicks. If you ride for 12-15 hours at a time, you will probably find that very little of that stuff works.
11. BB should be t47 68mm for ease of access, compatibility, and reliability.
12. Care should be taken to think about how the bike can be assembled/disassembled for travel and cleaning, as a gravel bike that sees even five tough events a year is going to need a lot of cleaning and will probably rack up 10K+km/year in training.

Interesting!

Is the spindle swappable for different lengths? Is it compatible with the Easton spindles?