An innovative tire design from Michelin makes vehicles equipped with it all but invulnerable to spike strips and other tire-flattening devices. Fear not, however — it’s not very likely you’re going to be chasing anyone who has these installed.
In 2005, Michelin introduced the Tweel, a portmanteau (that is, a word made up of two other words — this has been your capsule vocabulary lesson for the day, no extra charge!) of “tire” and “wheel.” A Tweel looks a little like an old-fashioned wagon wheel, with polyurethane spikes forming the spokes and conventional rubber making up the tread portion. The design completely eliminates the pneumatic tire casing, so there’s nothing for the quills in a tire-shredder to puncture.
Unlike a wagon wheel, the Tweel isn’t completely rigid. The polyurethane spokes flex under load, with the amount of flex determined by engineering. Heavier vehicles would have stiffer spokes, but all Tweel spokes would flex to some degree, so that the ride wasn’t too rocky. In fact, because the spokes on a Tweel are tunable both laterally and vertically, they could outperform tires of the more traditional design.
The design is far more environmentally-friendly than conventional tires. When the tread is worn down enough that the Tweel has to be replaced, there is considerably less waste material than would be the case with a standard tire. It’s even conceivable that a Tweel could be re-treaded, keeping the entire assembly out of a landfill.
So, why haven’t we seen more Tweels on the road? There are some performance problems that haven’t yet been overcome. The most significant issue is vibration. This isn’t a problem at low speeds, but above 50 mph, Tweels get palsied. This generates both noise and heat. The noise is bothersome to drivers, and the heat causes premature wear of the tire tread.
There are some Tweels out there, but they’re on low-speed vehicles, like earthmovers and Segways. In those applications, the absence of high-pressure tires is a big advantage, and vibration isn’t an issue because the Tweels never roll all that fast. They may also find a place on military vehicles, as they have better resistance to mines and IEDs than conventional tires, and they deflect shock waves away from the vehicle.