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This is just a little side project that I've been toying with, but I've been wondering if with the advent of tire inserts (CushCore etc.) it might make sense to take a new look at how tires are designed. If we conceptualize and design wheels, tires, and inserts as part of an integrated system, instead of as individual components, I think that there might be some real weight and performance gains available. And maybe, just maybe, we would see less World Cup and EWS races being decided by flat tires.
The tire has a variety of roles that are fulfilled by the tread and carcass. The tread is responsible for maintaining traction with the ground, but its ability to do that is directly tied to the performance of the carcass.
Meanwhile the carcass is responsible for:
1. Keeping air in the tire
2. Protecting the rim from damage
3. Providing sidewall support
4. Damping the rebound of the tire
Currently, most of the these design goals are accomplished by adding more material (and more weight) to the tire to create a more supportive and durable carcass.
Adding tire inserts to the wheel/tire system adds a new element into the system that overlaps with a lot of the same roles as the tire carcass. The insert also:
1. Protects the rim from damage
2. Provides sidewall support
3. Damps the rebound of the tire
I'm wondering if you could make a tire that would be both lighter and more resistant to slashes and punctures by designing it specifically to work with an insert. If you assume that insert will provide the majority of sidewall support, rim protection, and rebound damping that are normally a large portion of the tire casing's responsibilities, that frees up the design of the casing to focus solely on keeping air in the tire.
In essence, I'm wondering if you could make a casing that is made almost entirely out of a para-armamid, or an UHMWPE material like dyneema with just enough rubber built into it to provide for air holding. I've used dyneema slings quite a bit for rock climbing and in that application it can be woven into a fabric that is highly cut resistant and very flexible. If it was possible to build a casing this way you would end up with a casing that is very compliant and highly cut resistant, but it would offer very little sidewall support or rebound damping. However, if you can assume that these aspects of the design criteria are going to be carried out by the insert then that's not really an issue.
To take it a step further, if you design the rim to specifically work with a tire insert as well than you can eliminate some of the installation struggles that seem to be an issue at the moment. Based on Jeff Brines review of the Santa Cruz Reserve wheels it is certainly possible to create a rim design that is way less of a headache when installing an insert.
https://www.vitalmtb.com/product/guide/Wheelsets,44/Santa-Cruz/Reserve-Carbon,18736#product-reviews/2931.
Beyond that, I would think that you could shave some weight from the rim if you knew that it was always going to be used with an insert in place to provide impact protection. I'm not entirely sure about this notion given the fact that EWS racers are still destroying carbon wheels with CushCore in place. That said, the recent video of Danny MacAskill bashing the heck out of pair of the Reserve wheels without a tire certainly makes it seem like it would be possible to build them with a bit less material if the designer could assume that they would only be used with a tire insert installed.
https://www.vitalmtb.com/videos/member/Can-Danny-MacAskill-Break-the-New-Santa-Cruz-Reserve-Carbon-Wheels,34485/iceman2058,94
According to Flat Tire Defender using their insert means that a rim can handle 20% more force without suffering damage and I would imagine that CushCore would offer a similar level of protection. From an engineering standpoint a 1/5 reduction in the forces that a structure has to withstand is pretty significant and I would think that it would allow for a rim that could be somewhat lighter to compensate for the weight of the insert.
This has turned into a bit of an essay and there are obviously some complications involved with the idea like getting a rim, insert, and tire manufacturer lined up to work together; and bringing even more proprietary products into the market place. However, when you consider the fact that races at the absolute pinnacle of our sport are still being decided by the fact that we can't seem to keep air in a f#*%&ing tire, it seem like its something thats worth some discussion and outside of the box thinking.