You can’t inflate it – and you can’t puncture it. It always runs flat. Potholes don’t faze it – and there’s no possibility of bending the wheel because there isn’t one to bend.
That’s the hype for the non-pneumatic tire (NPT) and wheel – an integrated assembly made of a flexible polyurethane material formed into a spoked/honeycomb-like lattice around a central hub. The wheel/tire combo can deform with road imperfections and eliminates even the possibility of a flat tire, as well as the need to worry about keeping track of air pressure.
Some lawn mowers, golf carts and commercial equipment such as skid steers already have NPT tires – and the military uses them on rough terrain and in hostile conditions, where a flat tire can be more than just a hassle.
Resilient Technologies makes them for the latter – and Michelin (“Tweel”) Hankook (“i-Flex”) Bridgestone, Yokohama and other major players in the civilian tire business are developing them for possible use on the cars the rest of us drive.
Maintenance costs would be lower and – in theory – the hassles associated with conventional pneumatic tires (including government-mandated tire pressure monitors that often don’t work) would be things of the past.
It’s an intriguing idea – and it might could work – but don’t throw away your can of Fix-a-Flat (or spare tire) just yet.
According to Jacques Bajer, a tire engineer who helped to develop the low aspect ratio (short sidewall) tires that are common on cars today and who holds numerous patents related to tire design, it’s not yet known whether NPT tires would maintain their structural integrity over time, in the real-world driving conditions that passenger cars – as opposed to golf carts, lawn mowers, skid steers and military vehicles – have to cope with.
In particular, sustained high speed driving and cornering.
Bajer says the elastic spokes that support the car (in lieu of the air inside a pneumatic tire) might degrade over time, as a result of extended use as well as exposure to the elements. They could also be affected by extremes of heat and cold.
A major potential worry is physical damage to the spokes – which could unbalance the wheel/tire combo. Foreign material such as packed snow or rocks/road debris could get lodged in between the spokes, which could result in weird, even dangerous handling/braking characteristics.
Who’s gonna be the guinea pig? Who’s gonna pay the tab for the guinea pig’s class-action lawsuit?
No one really knows how long NPT tires would last, either.