Momo, sorry I didn't get to your question in the original thread. I've been a bit preoccupied with some matters that haven't allowed me my usual time on here, but I'll try to address your question.
As others have said, the 404 carbon clincher is not the ideal climbing wheel. However, given your preference for an all-around wheel I would say it could suit your needs quite well.
Regarding some of the points raised in the previous thread, the mass difference between the Enve 45s and the 404s is not as large as stated (actually over 25% less than stated), even going by claimed mass much less actual mass of test parts I've received. Regardless, inertial effects are much less significant than many believe, as they're only of relevance when accelerating (either in the axis of rider travel or when steering). I think we're all beyond examining micro-accelerations, and unless you're pulling Contador-esque multiple attacks in short order, inertia is highly overrated as far as critical performance metrics are concerned. Magazines love to include measurements of inertia as it's easily and inexpensively measured. This, however, does not imply its significance for many riding situations, and note that a 25% increase in a small number is a very small number (just taking an example from the previous thread purely at face value).
Addressing the issue of overall mass separately, our models have shown that a savings of 1 Watt via aerodynamic improvement equates to saving roughly 340 grams of mass for a rider on an 8% grade. This can also be verified via analyticcyling for anyone so inclined, or perhaps djconnel will interject. Regardless, this 340 gram savings resolves out to an actual resistance on the order of 30 grams in the direction of rider travel; obviously, this resolves to different values depending on the incline.
This is a difficult discussion that we've had with several of our pro riders...on some of the long stages in grand tours having multiple cols, they always want to ride 202s (see Carlos Sastre, Alberto Contador). However, if you look at the entirety of the stage, typically including long descents and stretches on the flats, their overall wattage savings would actually be higher with something like a 303 or even a 404. However, they invariably select the lighter wheel going either for just reduced mass in general or ensuring that inertia is as low as possible for that critical attack coming out of a switchback.
This overall savings with the deeper, heavier wheel occurs because aerodynamic savings will remain constant with velocity and no rider position and are generally of a much greater magnitude, even at lower velocities and generally higher effective yaw angles seen by most riders that aren't doping. The Hyperon was mentioned as a possible candidate but is somehow even less aerodynamic than a Ksyrium (I don't know, but the numbers don't lie), more than offsetting its lower mass relative to the 404. The plot below depicts drag force in grams (sorry djconnel) as a function of effective yaw angle. The same Vittoria 20mm Corsa Evo-Cx tire is used on each wheel, 4 runs each. Unfortunately, our database software doesn't display error bars but typical run-to-run variation is inside of 5-10 grams across the yaw range. Test velocity is 50 km/hr, which is obviously far in excess of most riders' typical climbing velocity but easily scaled to whatever speed you like. Standard conditions and pressure.
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These drag savings, even on the lower end of likely effective yaw angles, are an order of magnitude higher than the losses associated with the added mass of the 404 carbon clincher. The savings are reduced approximately 35% (and this varies depending on effective yaw angle) if you look at something like a Lightweight.
Most climbs I've done have a descent associated with them as well, and this is where the 404 carbon clincher will really shine. Over the past three years we've done extensive studies on refining stability in side force in terms of magnitudes of the side force itself, shedding vortices and the frequency thereof as it relates to the natural frequency of the rider/bike system, and the reversal of yaw torque. Much of this is covered in some of the CFD results that have been independently presented independently and is available in various places throughout the web; I believe some of the AIAA info is freely viewed but don't have time to dig for it just now. There's a brief description of some of the outcomes of these stuides in a mini-doumentary on our youtube channel that should shed some light on these issues for anyone that's interested: http://www.youtube.com/user/zippspeed
Lastly, our resin system used in the carbon clinchers was specifically developed with our supplier, as our lab and field testing revealed problems with several existing products that have been documented here and elsewhere on the internet. As we finalized an entirely new process of fabricating and molding rims and settled upon the resin system, we found that the glass transition temperature of our resin system is a minimum of 100〫Fahrenheit higher than any product currently on the market, and we did extensive work with our FLIR infrared camera to evaluate iterations of surface treatments and pad materials to ensure that we were dissipating heat as rapidly as possible. To date, we have yet to experience a field failure due to heat; that said, we're continuing to refine the process, material usage, and pad compounds to see if we can remove some mass from the rims, and in tandem we are refining the field and lab testing to ensure that any reductions don't adversely affect performance or durability for the end user. As many here know, engineering is about compromises, and in our case we elected to design for robustness; while we knew we were perhaps erring on the side of caution with our final production product and it is slightly heavier than competitive product of a similar depth, its durability thus far speaks for itself.
I hope that addresses some of the questions you had, Momo. If not, feel free to PM me as that is the best way to ensure a quick response.
EDITED for clarity and typos.