A Tire That’s Too Good to be True . . . ?

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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, NPT tires might not holdup as well 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) could degrade more rapidly over time, as a result of extended high-speed use as well as exposure to the elements. They could also be affected by extremes of heat and cold in ways that pneumatic tires aren’t.

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 vibrations and noise and possibly 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.

Conventional all-season radials often go 40,000 miles or more. For about $100 or so each. An NPT tire would have to match that – and for about the same money.

Now one knows what NPT tires – and wheels – might cost at the retail level. Remember: Instead of just changing out tires every so often, you’d be changing out tires and wheels.

But the biggest obstacle to NPT tires (and wheels) may be that they are severely ugly. Even if all the technical and economic issues are resolved, will buyers cotton to these things? Would you? Have a look. It’s like mounting cat scratchers on your car.

So why the sudden interest – by so many major tire companies?

Because of the environmental angle.

Hankook’s i-Flex NPT tire, for instance, is said to be made of “Eco-friendly” materials designed to be easy to recycle. It’s also touted that less oil (which goes into conventional rubber pneumatic tires) would be used and thus, Gaia smiles.

But – as is frequently the case with anything “environmentally friendly” – the price isn’t being talked about very much.

And – leaving aside potential performance/functional/aesthetic problems – cost matters.

Well, to tire buyers it does. Maybe even more so than looks.

People will buy an ugly car. . .  if it’s a good car. And even more so if it’s an inexpensive car. But an ugly – and expensive – NPT wheel/tire? That might be something only a government bureaucrat could love.

What if the bureaucrats mandate or otherwise government-push (as via subsidies and other “incentives”) NPT tires onto the market before they are functionally or economically viable – and notwithstanding that they are harder-on-the-eyes than a close-up view of Hillary Clinton’s face – in the name of “environmentalism.”

This sort of thing is not unheard of.

Electric cars, for example.

Once government decides something is good for us, it often ends up being forced on us.

And that includes the bill.

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  1. Are there other engineering options you can implement to address the issues of a solid tire? Why does the tire itself have to address it all?

  2. You are not going to be torquing lug nuts to rubber wheel centers, so there must be some sort of steel to rubber bonding area.That area will see extreme torque as the axle shaft transfers power to the NPT outer tread. I have seen many rubber to steel bonding failures. If such a failure happens here, then it would be like having a wheel come off on your vehicle.

  3. So I must confess that nearly two decades ago, as a young tire chemist at Bridgestone, I asked the question “why do we still have air filled tires”? And having just knocked my first major development project out of the park, my supportive, well intentioned bosses actually took me seriously. So with apologies to all I fear I may have helped put this in motion. Now granted my intent was never to replace the WHEEL, I was thinking of something more like a blown foam or gel type core. And we actually prototyped some very low-pro solid tires on aluminum wheels that returned some phenomenal test data (like near zero rolling resistance that could double fuel economy) but with some tricky trade-offs. Unfortunately for all of us I left the company shortly thereafter and things went off the rails. This tire wheel concept was already in the public domain and like so many Japanese companies, Bridgestone dropped my more lofty aspirations and followed the leader. This is the result.

    So to address and concur with many of the comments here, my general opinion is that there ultimately is a future, advantage, upside etc to solid tires, but this incarnation is definitely not it. If I learned anything working at Bridgestone it was definitely (more than I ever wanted to know) about the effects of shear stresses on the lower and upper sidewall (think Ford Explorer Wilderness ATs). Every tire has a bead that is basically a thick steel cable that absorbs the stress transfer between the wheel and tire. Replace that with a rubber to rubber interface and start taking turns at highway speeds and you better be right with God, cause you’re gonna meet him. I honestly think mud and snow would get spun out pretty easily, and you could design the ribs in the wheel component to facilitate that, which we’ve done with treads for decades. But putting the entire stress of a car in a tight corner across a rubber to rubber interface is suicide. I’m convinced we can do better than air filled tires, but what was wrong with wheels in the first place? Nothing that isnt wrong with a rubber one that costs more, can handle less and has to be disposed with the tire. So funny that the same industry that slits its own wrists to meet fuel economy standards made for the sake of the environment has decided to put 3 times the rubber into landfills. I know so many of these people and they are so smart and so capable but this lunacy tells me they have lost their way, their minds, or both.

  4. Speaking of solutions in search of problems that don’t exist….remember ” 4-wheel steering”? That nonsense didn’t last long, did it? (Thank goodness!(

  5. I wouldn’t care if they outperformed everything out there and cost 2 bucks a piece. They’re as ugly as Phyllis Diller driving an Aztec, NO THANKS !!!

  6. I am 100% positive that in spite of their supposed “interest” in the technology, the TIRE Manufacturers will somehow manipulate uncle into OUTLAWING any tire / wheel combo that can be 3d printed.

  7. What do you do when the honeycombs get full of snow, or mud? That would throw the balance way off. And it would add to the weight,, though extra weight may be good for traction in snow; not so good in mud.
    Expensive, and impractical. Keep working guys. 1% inspiration, 99% perspiration.
    Why not just fill a pneumatic tire with some kind of resilient foam like material, and air. If it loses air, then the foam holds it up till it can be repaired.

  8. It has to be said though, the idea that even today we are STILL relying on balloons of air is pretty ridiculous.

    You don’t think so? Try changing a flat rear tire when scrambling off road and around 2 hours into the ride, halfway up a mountain?

    There are a couple of options for off-road bikes now, though not available here in Malaysia, ‘Tubliss’ and some other thing. But really, the idea of inflated balloons, ones which occasionally go “BANG!” and cause fatal crashes as well as the inconvenience of a flat makes the “technology” of pumped-up tires pretty damn stupid.

    We had pump up tires on bicycles as a kid and punctures were a real PITA back then. I’m an old goat now, and we’re STILL doing the “pump it up with air” thing?


    Sure, a stupid design where you have to replace the entire wheel is indeed stupid, but something better than balloons would be great…

  9. Sounds like another scam to me. Improving something that doesn’t really need it. My stupid car just had new tires put on–$400 total! Insane, right? I used to think $200 for four tires was a ripoff, lol!

    Come spring, seriously going to begin phasing cars out of my daily life, just too expensive, damaging to health, and so on.
    Not to mention exposure to our hero’s in uniform. Safety, sure, I’m all for it, but I should get to determine at what price mine is worth…….ship sailed and all that.
    Screw all corporations anyway, I’d rather give my dough to a local bike shop.

    • good on yer for the bike shop idea. You’ll still be healthy and strong when all your pals are dying of cancer, emphysema, strokes, hearts quitting….. I calculated it all out a few years back.. realised I’d seem spending a LOT of cash on rea nice expensive bikes, but I also rode a whole lot and used the bikes to get where I’d normally drive… often a hundred miles a day. I did some calcs.. admittedly back when diesel was five bucks the gallon, but still… I log my miles and compared what I’d spent on nice bikes, tyres, etc, against the miles I’d ridden them for the past few years, and it turned out the bikes were free, compared to driving the same number of miles. And I had got skinny and strong.

    • Hi Andy,

      Agree… owning a car has become an expensive hassle; the opposite of fun. I am certain this accounts for the declining interest in cars among the younger crowd.

  10. I’ve seen these at trade shows. They are clearly only useful for off highway stuff.

    Regular air filled tires are entirely recyclable. The technology was invented many years ago. The materials just aren’t worth the energy cost of the process. But tire use ground up has numerous options.

  11. The reason these things are relegated to golf carts and tractors is that the “tweel” has horrible vibration resonance problems at anything approaching highway speeds. Pneumatic tires are wonderful at absorbing vibration and don’t have this issue.

    For now, the safety-nazis are fighting the eco-nazis, so nothing is being forced on us just yet, and I doubt that it will be mandated anytime soon. The technology simply isn’t ready.

    On a side-note, I’m floored by how many people I see driving around on completely flat tires. How can you not notice this, given how much it affects the handling of the car?!

  12. I wouldn’t want to have to trust those things taking corners at highway speeds.

    As to tread wear, I’d think that they’d be much easier to retread than conventional car tires, adding to their green appeal. They’re already separate pieces as it is, just a new tread and a new bond needed.

    But lacking sidewalls for flex for taking high-speed corners, I’d think these things are very dangerous for normal car operation. They do have their place in off-road and commercial roles though.

  13. One all too common situation in all things mechanical and medical I have seen happen is that of “solutions” to problems that really mean merely trading one problem/set of problems for another. Case in point: I asked my eye doctor about Lasix. He said I’d be a good candidate, but it would mean that I would still need glasses, but for reading instead of driving. So no Lasix for now.

    These NPT things are a lot like that. Sure you don’t have to worry about a flat tire, and they last longer. But they don’t last even for the service life of your car. And instead of spending, say, $500 every 60K miles, you end up spending $1200 every 75K miles. So where’s the savings there?

    There is also what I will coin “The California Conundrum.” These new technologies, like self-driving electric cars made of unobtainium, are often tested and rolled out in the California coastal areas. They may work there, but not so much elsewhere, where you have things like extremely hot or cold temperatures, heavy rain or snow (or any rain or snow for that matter) hills, rough terrain, bad road surfaces, and sharp curves.

    I wonder, for example, how these would hold up after driving through deep snow along a Colorado highway, or if the desert sun of Arizona would make these wheels degrade like it does to dashboards. And if you’re driving the twists and turns of a road winding through the Appalachian mountains, how would they handle?

  14. “(including government-mandated tire pressure monitors that often don’t work)”

    I imagine you’ll need to fit some sort of tire pressure sensor on these to keep the idiot lights from going off all the time. I doubt many first generation TP sensor equipped automobiles have a way to disable the alarm, and getting permission to disable the alarm is likely illegal, even if only in a mattress tag removal way.

  15. Why is this being discussed again? Close to a decade ago the verdict was in on the NPT’s of then and it sucked.

    There are lots of things to consider first being reliability which wasn’t good and cost which was worse. Oh, I’d take a set on a skid steer and maybe even something like on a truck that never needs to be off-site. But we have a lot invested in wheels now…..once. So, are we going to have to buy the equivalent of a new wheel with a new tire or are they just going to be marginally, say 50% more expensive. With my small 265/75/16 load range E tires, I’m only looking at say $800 set……only. So it goes up to maybe $1200 and a third the life in distance? As long as they’ve been around I don’t see them being a road tire in the near future. Have spare, Will travel.

    • Give ’em a soft enough rubber compound on the tread to maintain good traction, and they ain’t gonna last too much longer than a standard tire; Then when ya gots to replace ’em, you’re essentially replacing a wheel and tire instead of just a tire.

      Seriously, who thinks of this crap? The same geniuses no doubt who said we’d be living in colonies on the moon while driving flying cars….and roads that act as solar panels…and $130K electric cars…..

      Gosh darn, this world is NUTS!!!!

  16. I would love a set for both of my skid steers. Flats drive me crazy on those things. Backhoes, loaders and trucks would be great too. But cost is important. I saw these a couple years ago for skid steers but never saw a price. Even michelin’s web site is hard to navigate for info on them.

  17. “…it’s not yet known whether NPT tires would maintain their structural integrity over time…”
    Of course they wont. Or more correctly, it is most certainly known that they will lose their structural integrity over time, the only question is how long and under what conditions. Still, kind of an interesting option. Could be tried in bikes first (NOT motorcycles!) Might be great on light aircraft- what with tire pressure on the ground having to be low enough to withstand high altitude external pressure.

    Are they really any uglier than twenny fores???

  18. Interesting. Seems like balancing deflection (for decent ride comfort) vs. load-carrying ability vs. durability might be a tricky thing though. Kinda hard to compensate for just being able to add or release a little air in a regular tire. Plus, I don’t think Oncle would approve, as they’d be impervious to spike strips.

    Seems like another high-tech solution to a problem that doesn’t exist.

    They’re always coming out with all this fancy crap. Maybe instead, they should just concentrate on making the simple, proven things that really work, really good.

    • Interesting that the military uses them, although not real specific as to what vehicles they use them on. One of the more interesting features of the HUMVEE was that you could adjust air pressure on the fly to match conditions, something 4 wheelers have been doing from the beginning by converting air conditioning compressors to air pumps.

      • Hi Eric,

        Even if they work brilliantly (and inexpensively) I think they are hideous looking. Even worse than gnomesayin’ “twennyfows” on a ’77 Malibu…

        • The military has a different set of priorities than civilians. When people are shooting at you, stopping to change a flat is a bad idea. And combat effectiveness is about utilitarianism, not looking pretty.

          Now, if they can get the cost down so they are competitive to conventional tires, make them a lot prettier, and prove their reliability and able to handle well in a wide range of climates, then maybe they might make sense for civilians, at least in some applications. Right now, though, they appear to be the tire equivalent of an overstressed tiny expensive turbo’d four replacing a durable understressed V6 or V8.

          • And also, money [our money] is no object to the military- the organization where they pay $5K for a toilet seat. The same bunch who buy bilion-dollar jets that can’t fly….

        • eric, best I recollect, shock design was also a problem as well as springs. You can’t change one thing without affecting everything else as I’m sure we all know.

          Chrysler put torsion bars on their cars way back and what a relief it was that GM began doing the same on 4WD pickups. Shit Ronnie, if it ain’t broke, don’t fix it.

          I’m still trying to figure out why companies haven’t wised up to low profile pickup tires although some never bought those things in the first place. I know my 4X4 one ton won’t handle as well(bare) as the ones with low-pro’s but load out a big gooseneck and see how well that low sumbitch does as it is run flat and the driver doesn’t feel it until it comes off the rim in pieces and you’re going around a hard curve.

          I was at Wally the other day and this jacked up Yukon is sitting there with huge chrome wheels and nearly tires and I notice the RR is almost flat. Nobody around so I let nature take its course and walked on. It probably had a tire monitoring system on it but the people installing those huge wheels probably didn’t bother to find some that would work with them. Stupid is as stupid does.


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