A startup called the Smart Tire Company has licensed NASA's airless tire technology, and adapted it for bicycles.
NASA's non-pneumatic wheels, intended for interplanetary rovers, look like this:
These "shape memory alloy radials" rely on the spring-like strength of alloys, rather than air, to provide the cushioning and deformability required of a tire. Initially, the Smart Tire Company used the concept to design this wheel for a gravel bike:
They've now refined and simplified the design into this METL wheel below, which essentially uses a spring, wrapped into a torus shape, to provide the structure for a wheel:
That wheel is then clad with a replaceable rubber tread, which requires 50% less rubber than a conventional bike tire:
The METL wheels work on standard bike rims, and the company reckons their NASA technology means they'll succeed where others have failed:
Airless tires sound great, but they usually fail to deliver…. Major tire companies have mostly given up on airless applications altogether: the ride is rough, and/or it's more work to pedal (high rolling resistance). Why? They're using the wrong materials, stuck in the era of rubber and plastic.
METL tires are powered by an inner skeleton made from a modern material called Nitinol, a shape memory alloy. It's a lightweight, highly flexible "superelastic" metal that stretches like rubber, but is strong like titanium [and] will always instantly snap back into its original shape.
Nitinol/SMA properties include:
- The highest energy return of any material previously used in any tire (fuel efficient, lower rolling resistance)
- Shock absorption & elasticity (smooth ride)
- Extreme durability, but still lightweight, due to unique properties of the material
- SMA tire internal structure can last the life of your vehicle, so one set of tires is all you'll ever need
Save TIME & MONEY with zero flats, no air pressure to check, no sealants, no inserts, no foams, no patches, no spares, no expensive replacements, and no more being stuck in the middle of nowhere carrying or walking your bike. No more worries. Just ride.
The company says the METL wheel is suitable for pavement or gravel. They're manufacturing a limited run and selling them through a Kickstarter campaign, which has already been successfully funded, with 27 days left to pledge at press time. Buy-in starts at $500 for a pair of METL wheels with no rims, and $1,300 for a pair that come with aluminum rims. They're also offering pricier carbon fiber rims starting at $2,300.
The METL wheels are expected to ship in June of 2024.
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