SMART Tire Company & NASA METL Pneumatic Smart Bike Tire
We're used to seeing bike tires made of rubber and filled with air. However, as it is today, they're prone to punctures and damage, which can be very inconvenient especially when you're on the road or on a trail. It also leads to a lot of toxic waste.
SMART is part of NASA's formal Startup Program that aims to commercialize some of its innovations.
An airless bike tire is its first product and it is called METL, which is the acronym for Martensite Elasticized Tubular Loading. It's basically a fancy way of saying super-elastic metal.
METL uses a material developed by NASA engineers Dr. Santo Padula and Colin Creager at the Glenn Research Center in Cleveland. They call this material the shape memory alloy.
Shape memory alloy is an extremely elastic material that will always go to back to its original shape when it is above a certain temperature. It's a spring that will never lose its springiness.
This springy material is woven together in a chainmail-like mesh to provide a support structure that flexes like a rubber tire.
Since no air is needed to retain its shape, the METL tire is entirely flat proof.
Not only is it elastic, the material is also extremely tough. According to Calvin Young, Smart Tire Company's mechanical engineer and one of the creators of the tire, you'll destroy a rim before you'd damage the tire. It is virtually indestructible.
One problem with the chainmail-like mesh structure of the METL tire is that it is susceptible to debris getting into the holes.
Using rubber on the outer layer could probably overcome this problem. Instead, a material called Polyurethanium. The properties of this material is not disclosed except that it is intended to at least have similar tread life to conventional tires.
The difference is that the metal tire can be re-coated when the Polyurethanium is worn out.
The same material will also be providing grip for the METL tire.
Other issues include the coefficient of rolling resistance and how to vary the tire's stiffness for different riders and terrain.
The current prototype is said to mimic the ride of a 700cc clincher tire at 100psi.
Will it replace conventional tires?
At its current state, it probably won't be replacing conventional tires anytime soon. According to tire's creator, Young, its first and likely best application is for bikeshare rides and other fleets.
Bikeshare uses are not as sensitive to ride quality issues as enthusiast cyclist are.
There seems to be a lot more work to be done before the METL tire can be good enough for road or gravel or mountain bikes.
There's no telling if the technology will even make it to performance bikes but if all goes well, we can expect to see these airless, indestructible tires on bikeshares in 2022.
An indestructible tire that doesn't require air seems like a good idea. However getting it to real world use have proven to be difficult. Michelin and Bridgestone have tried for years and have yet to be successful. Now even with NASA's help, the best they could do at the moment is bikeshare application. Perhaps in 10 years, we will see punctureless tires on performance bike. Perhaps not even then. They say it'll only take a few more years because the technology is already here and that it just needs refinement. Maybe they're right. But how can they can know it's the right technology that will lead to what was intended? - the end of tire punctures.
If you're interested in investing in the Smart Tire Company go to their wefunder page.