The Daily Bike, November 6, 2012

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No, this isn’t a tubeless mountain bike tire. It’s an “airless” tire, really a rubber rand supported by a strut system that works (its inventor says) like a 360-degree spring to return rolling energy into forward momentum, which is why it’s called the Energy Return Wheel. It’s way cool in theory, because never having to hassle with tubes, or tubeless, would be ridiculously awesome. And just think of all the tires that get toasted by a thorn or baby head that go straight into the landfill.

But…I have my doubts.

First, eyeballing the video below, there’s no such thing as a sidewall. Lay the bike over in a turn and what happens when you’re no longer rolling on rubber? More critically, there doesn’t seem to be a heck of a lot of deformation happening. That’s supposed to be an advantage (energy return means the spring-loading effect is pushing you along), but one of the reasons tubeless tires rock is that they do deform to put more rubber on the ground for traction. Supposedly the ERW has adjustable carbon struts; softer struts give more cushion. But you don’t want cushion; you want adhesion, grip, stickiness. And if you think of the micro adjustments you can easily make with just plain old air…well that’s not going to happen here. Then there are other factors: cost and weight being way up there. Anything with carbon is costly, and carbon out there at that really vulnerable end of your bike after a sweet huck…to flat…oops.

I’m not saying it’s not interesting. I’m just sayin’.

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{ 16 comments…read them below or write one }

  • Hotmann

    I would love to have something like this for a city bike, but on the mountain I like the ability to change tire pressure depending on the trail I’m riding. Hardpacked and fast singletrack, put in a little more air. Rocky or sandy and drop the pressure for more grip. I don’t see that happening too soon with airless, unless you have a bunch of different tires to switch between, but that’s annoying.

  • Jay Goodrich

    I with you on this one Steve. The thing that I also see in the video is that the rider isn’t really trucking along. That immediately makes me think I would smash this thing to billions of pieces on anything over 5 MPH and conditions other than perfectly soft trail.

  • Leon Shaner

    Looks like those would be cool, however I can imagine they would not be so nice in mud…particularly the “greasy” clay-like mud I so often find myself in (here in Michigan). That kind of mud would likely fill the “tires” and would not so easily come out, even in water, so it would make for a very heavy bike at that point. :-/

    Seems like most likely these will be perfect for dry/desert climates where goat head thorns are a serious problem.

  • Andreas

    Cool invention! While I see some issues with the current state of this system (e.g. those holes in the sidewalls are not really practical…) I also see the potential of this new invention. Imagine, cycling without carrying a pump, patches and spare tubes! Even without having to use them at one occasion and saving energy on propulsion on top…

  • Tyler

    This kind of technology already exists for cars..see Michelin’s “Tweel” http://en.wikipedia.org/wiki/Tweel

    If it’s engineered right, I’m sure this tire can take all the huckin’ you’re ready to dish out. Best argument I’ve heard against them so far is the ride tunability you get with air.

  • gnarlydog

    not buying it, for the same reservations expressed above.
    As far as puncture proof, I rode for a few years with Stan-No-Tubes and despite my best efforts of running purposely into cactus my tires would not deflate unlike with conventional tubes.
    I am picky about what tires I run on my MTB (some tires suck) so I can see limitation on thread choices with this system.
    Nice engineering exercise tho

  • B Sweet

    I think this could never overcome the cost/benefit of any tubeless w/sealant pneumatic tire system. I “tune” my tire pressure regularly on the trail because, as others have mentioned, I find it’s critical to find that balance between comfort, traction and rolling efficiency. But I do hear they’re working on using vacuum charge to adjust the wheel stiffness or flex. It’s starting to sound like then the only benefit is durability if you have to maintain vacuum pressure. Sure looks heavy too. I wonder if the gravity guys might see a benefit. As a XC rider that enjoys my stans-no-tubes wheel-set I certainly do not.

    …I could see this in a road bike though. Perhaps this invention could be integrated into a carbon rim? Then somehow make the tread replaceable/removable (post-tubular) or just make it a raceday wheel-set. I can imagine super low rotational weight mated with disc hubs and maybe sub Kg static weight with the “tire” integrated into the rim. Wait maybe I should just invent this myself….. *runs to patent office*

  • Erik

    There have been some interesting similar ideas for automotive applications, which makes more sense since you are not laying the wheels on their side to turn, which would be an issue on a bike, as pointed out alerady. Can’t access the video at the moment, but the thought that any energy would be transferred back to forward motion is certainly bogus. The force on the wheel is straight down from the axle, torque applied to the rear wheel to provide forward propulsion through the friction from that contact patch. The only direction of force the wheel’s spring could act is straight up from the ground towards the hub. If you’re in a pump park, and you hit some terrain just right, this could propel you, but I seriously doubt it would ever work in practice.

  • Andreas

    @Tyler:

    But then, if your a big bloke like me, there’s not much in terms of tunability – I basically ride my touring bike with max pressure on the rear wheel (recommended by the tyre manufacturer anyway). The front wheel would allow for some tuning, but then, what’s the point of it?Another consideration, road racing bikes are usually ridden with max tyre pressure for best performance, as are (fully-) loaded touring bikes for best tyre mileage. That basically leaves MTBs and city bikes. The rider of the latter perhaps won’t mind and except for traction I also don’t see a real need for adjusting tyre pressure in MTBs due to suspension unless one plans to cross a desert with a fat-tyre bike.

    • gnarlydog

      @Andreas
      >>don’t see a real need for adjusting tyre pressure in MTBs due to suspension<<
      hmmm, not sure what kind of MTB riding you do but when I used to wrench for a national team on NORBA tyre pressure was extremely critical for my riders on dual suspension. That goes for me too, and suspension has little to do with tyre traction. Pump tyres to 60 PSI on a light rider's bike and see what I mean.

  • cafebmw

    more rubber on the ground does NOT equal more traction. that’d against the law of physics. traction is a function of the friction coefficient and the weight. the contact area is not part of the equation.

  • Rob

    @cafebmw Really Einstein? and where exactly does the friction come from if not the contact area? I suppose they make dragster tires with so much surface area just for kicks then.

  • Andreas

    @gnarlydog:

    To be honest, I havent’t done much MTB riding recently, let alone any on a more professional level ever. Personally I still don’t see the need for adjusting tyre pressure (on a regular base) except for riding long stretches of soft ground (sand, etc.). In fact, I am more bothered by tyres loosing pressure than being too tight. Anyway, if tyre pressure is critical to (some) MTB riding, there’s no law preventing sticking to inflateable tyres.

  • cafebmw

    @ rob, dragster tires are made from extremely soft compound. that is what improves the friction. they are just wider to last longer. imagine a narrow tire with the same compound, it would smoke up right away.

  • Einstein

    cafebmw is completely correct. A larger contact patch has nothing to do with friction. The only thing that determines the force of friction between two objects is the coefficient of friction between them.

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