When you’re exploring another planet, the last thing you have to deal with is tire damage when AAA is millions of miles away. It is a concern that led NASA to develop a airless titanium tire which is flexible like rubber, but almost indestructible. As has been the case with many of NASA’s inventions over the years, that space-age tire technology will soon be available to consumers.
Using air-filled rubber tires on a vehicle is not a practical solution for exploring nearby celestial bodies whose natural terrain is covered with rocks and sharp objects. So for the handful of wheeled vehicles NASA has sent to the moon and Mars, metal wheels are a better alternative. For the Lunar Rover, which Apollo 15 brought to the moon, wheels were created made of hollow metal springs that could absorb shocks to make travel more comfortable for astronauts. But most metals lose their shape over time and become brittle when repeatedly flexed, resulting in misshapen wheels that don’t roll as well and worse, serious damage that prevents them from rolling at all.
As an alternative, NASA has spent several million dollars in the past seven years developing Nitinol – a metal alloy made from aluminum and titanium that behaves differently. Metal springs eventually lose their ability to return to their original shape because the bonds between their atomic structures are stretched so much that they can no longer return to their initial arrangements. But Nitinol exhibits a neater atomic structure and exhibits something known as a shape memory effect, which allows it to warp but revert to its original manufactured shape over and over again without permanent damage. It allows you to create metal tires that can be deformed to absorb the impact of uneven terrain such as rubber, without the possibility of a puncture.
It’s an incredible technology that will soon be available in the next few years for a vehicle that will likely never leave Earth’s atmosphere: your bicycle. A startup called The Smart Tire Company has announced that it is creating a metal bicycle tire from NASA’s Nitinol alloy that never needs to be inflated, will never leak, and will likely survive much longer than the bike itself.
Called the METL (Martensite Elasticized Tubular Loading) tire, its creators hope it will be available as an alternative to premium bike tire options starting in 2022. It remains to be seen how much a titanium alloy bike tire will cost, but you can. Suppose it will be a long time before the children find a Nitinol wheeled bicycle under the Christmas tree. However, for riders who are happy to spend tens of thousands of dollars on their bikes, METL tires might be the last set to buy, although they will still require regular maintenance.
The most common problem with airless tires is that they often feature open-frame designs that can allow debris to enter and upset the wheel’s balance. Using a metal frame instead of rubber complicates things even more because the smooth finish means the tire doesn’t have much grip. To solve this, the METL tires will also be finished with a rubber-like tread made from a material called polyurethane that adds grip and makes them suitable for riding on all terrains, including pavement, gravel, and dirt. Over time, the tread will wear out and will need to be reapplied, but maintenance is expected to be much cheaper than having to regularly replace a set of tires.
METL tires are not suitable for all cyclists. After all, they are made of metal and are expected to be heavier than the premium lightweight tires used by professional cyclists and athletes. But for most other applications, including athletes using larger bikes on off-road terrain, the tires won’t feel any different during a ride.
The Smart Tire Company is making a lot of promises about the advantages of its Nitinol tires over rubber ones; check out this extensive Frequently asked questions on your website promoting the virtues of technology, and there are good reasons to be excited about technology. Obviously, NASA felt it was important enough to spend millions of dollars on its development. But we have been promised airless tires for many years, from industry giants like Bridgestone, who have the manufacturing capabilities to make them happen. However, they are not here yet, not even for bicycles, which is the least demanding application for technology.
There is no doubt that one day punctures will be a thing of the past, but will it be thanks to the efforts of this startup? If you can deliver METL tires in the next two years as you intend, there is good reason for Michelin, Goodyear and Bridgestone to be concerned.