Zipp's clinchers are built with the aluminum and carbon mated together in a structural manner: http://www.zipp.com/...s/composite/m2cm.php (there's a picture in the catalog). Basically, this presents additional challenges above a wheel that is simply a fairing bonded to a standard aluminum hoop both in terms of manufacturing and also in terms of structural design. Zipp did a lot of work to get the balance of weight and strength right. I tested both the version you can buy and a lighter one you cannot. Ultimately, myself and the other test riders and the folks at Zipp all came to the same conclusion - some additional weight (which in terms of percentage of total wheel weight is relatively small, i.e. the 1080 is a heavy wheel in the first place, so a bit of additional weight is probably not going to tip the balance from someone deciding, for example, to use them for a hill climb or not) for additional strength and reliability was worth it. It's relatively easy to build a light wheel that doesn't last or that has a rider weight limit or which can only handle very low pressure in the tires, but I don't think that's a product that belongs in the mass market. Of course, some people do. Ultimately, the 1080c wheel that Zipp released was what a lot of people felt was the best overall balance. Is it heavy? Yes. But on a two week trip over the summer I rode that wheel and my clincher disc every single ride, on some roads that were about as bad as you can imagine, in all kinds of weather, and it never missed a beat. I hit some big potholes, and the wheel handled them just fine. For me, that's worth a whole lot more than grams, and I think (hope) that average customer would agree.

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"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

Thanks for the "inside" response... I understand the construction process and the rational behind choosing strength over weight, but it seems like there is something else... The percent increase is higher for the 1080 than the 404 or 808 (which are identical). Which suggests that the 1080 was designed to have greater impact resistance or rigidity in the rim than the 808 or 404. I would have assumed that it would have the same design "factors of safety" as the 808 or 404. It is possible that the forces in a deeper rim are different than for a shallow rim, but then why would the 404 and the 808 be the same?

I don't think the weight is an issue, I just find the design interesting and wanted to know the rational behind it.

I love the 1080 Clincher BTW; it is the stealth bomber of rear wheels.

So the design rationale was that, hey, this is a TT wheel, weight shouldn't be an issue, so lets make it stronger than the 808 and 404?

In practice the weight shouldn't matter. Mentally though, the weight difference big. 2358g for the 1080 clincher, 1663g for tubular ( know you asked about clinchers). That's 1 1/2 pounds which is quite a difference on just wheels. The construction method should make these very strong for larger riders however.

your explanation is understandable, but it still dances around the basic question that was asked. because what you are saying can really apply to any tt wheel that zipp makes. so if zipp decided to go with more weight in the clincher 1080, why exactly did they make different decisions for the clincher 808, or clincher 404? are you saying that because of design decisions, that the clincher 808 is a fundamentally less reliable wheel? why did not zipp make the clincher 1080 wheel with about the same level or relative weight and reliability as the clincher 808? what is different about the clincher 1080 that made zipp make quite different design decisions? i think this is the real enigma.

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Where would you want to swim ?

I suppose there was some dancing. It's hard to answer the question without getting too much into details that I can't share. And I realize that is not really an answer either. I guess the simplest answer is that the additional depth of the 1080 provided unique design constraints. Furthermore, any changes to the structure of the wheel would magnify the weight difference due to additional depth. You seem to have a pretty good handle on this sort of stuff, so I think you can probably figure it out for yourself if you think about how the clincher wheels are made and what could cause that jump in weight. For whatever reason, the 1080 seemed to pass a certain threshold that required the additional strength that the 808 and 404 did not. Things do not always scale linearly; it is actually quite common in engineering to see big jumps as you pass certain thresholds where suddenly things that were not an issue at a smaller scale suddenly come in to play. I'm reminded, for example, of the early days of bridge building. Once you reach a certain size of suspension bridge, the weight of the bridge itself becomes a major factor. Or, of course, the famous case of the Tacoma Narrows Bridge, where the bridge was actually so light - due to improvements in construction - that it became very sensitive to winds. In that case, the improvements in technology allowed the builders to build a "better" bridge that was actually worse, because suddenly they had a whole new set of problems to consider. While that is certainly a much more dramatic example, the 1080 is similar. Building a wheel of that depth the exact same way as the 404 and 808 ended up not being an acceptable solution. All wheels - and really any structure - has a point at which it will fail. So from that perspective, yes, Zipp could make both the 404 and 808 stronger than they are currently. That is why there are the impact standards and fatigue tests. The 404 and 808 were able to meet Zipp's standards at a lighter weight relative to what it took to make the 1080 meet the standards Zipp set for it.

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"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

I would think that as the rim depth gets deeper, the distance between the edge of the wheel and where the spokes attach necessitates a beefier (hence heavier) cross section because torques on the rim are magnified. An exponential scale-up of weight makes sense here.

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