Prototype wheels could take the flats out of mountain biking – and driving
The mountain bike version of the Energy Return Wheel, being put to the test
Puncture-proof tires that incorporate a flexible internal matrix instead of air are nothing new, in and of themselves. In the past several years, we’ve seen prototypes from the likes of Michelin, Amerityre, Goodyear and Bridgestone. Colorado-based Britek Tire and Rubber has also been developing something similar, known as the Energy Return Wheel. While the ERW is intended mainly for cars, the company recently released a video showing a prototype set of the wheels in use – on a mountain bike.
The automotive version of the ERW is said to not only eliminate flats, but also improve fuel efficiency and performance. Each wheel has a layer of rubber at the center, that is stretched and held taut by adjustable rods. A rubber tread is on the outside (as with a regular tire), while a series of elastic cushions occupy the space between the two – this is the area that would ordinarily be filled with air.
According to Britek founder Brian Russell, the stretching of the internal rubber layer allows elastic potential energy to be stored within the wheel. As that layer is compressed by bumps transmitted from the road, the stored energy is supposedly returned (hence the name) and converted into forward momentum. It is also said to press the tread onto the road instead of allowing it to bounce off, as is sometimes the case with pneumatic tires.
It’s an intriguing concept, but needless to say, if any engineers or physicists would like to weigh in on the matter in our comments section, we welcome your input.
The new mountain bike version of the wheels incorporate lightweight 29-inch carbon fiber rims, and (like some of the automotive prototypes) are open on the sides. Russell is wisely considering adding thin sidewalls, to keep mud and trail debris from accumulating within them.
Although there is no air pressure that riders can adjust, they can instead adjust the rubber-tensioning rods to make the wheels run harder or softer.
The mountain bike ERWs can be seen in use in the video below.
Source: Britek Tire and Rubber via ChopMTB
About the Author
An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away.
All articles by Ben Coxworth
It's possible they simply had the rubber tension very.. tense.
When they f i n a l l y get around to showing the rolling tire from the side near the end of the video I do not see any flex or give. They look like they ride like a rock. I would not buy them because you need that flex for traction on the dirt. Besides that they have no side tread for the corners. But keep trying because no flats would be a dream.
I agree with the Hoff. They need compliance for traction and side tread for railing corners. However that compliance must not be lateral or the tire will roll in hard corners and annoy the rider. Unless these are lighter than a tube and tire, you're better off marketing to the baggy shorts DH crowd. Model the tread after the High Roller 42a, and or the Minion DHF 42a and you'd have a hot product.
Great idea, keep working on it.
Reviewing the vid, I saw several instances of where the tire gave and flexed. These tires are geared for mountain bikes in this example, not your street racers.
Well-designed experimental comparison is better than theoretical analysis in proving whether "Energy Return Wheel" is not just marketing jabber.
Still, there are cases when any possibility of the punched tire must be eliminated regardless the cost or fuel efficiency.
Try Basalt fibers instead of carbon fibers for the frame. Basalt takes impact very well-and is easily three-four times less expensive. It has great spring modulus-17.5 percent better than a high end S-glass. http://www.basalt-mesh-fiber.com/
These tires might work but also might not. Bicycles distribute shocks in an air filled tire over the entire tire. In a foam filled tire the shock apparently is more local and wheel wear and failure are more of an issue. In essence you could go to WalMart and buy a solid foam tube right now and drill windows in your sidewall and have almost the same thing as this new tire system might offer. Although I have read that pro racers at Tour De France are now beginning to accept foam filled tires so maybe there is hope.
'Resilient Technologies' have also been in the airless tyre game with a similar design since 2005.
While the concept of an airless puncture-proof tyre is noteworthy, I think they're making some bold claims with the supposed performance enhancements. Their claim of 'energy return', where the compression from a bump is converted into rotational momentum... is imaginative.
I've watched the video on their website about 10 times, still can't understand where they think the free momentum is coming from. That would seem to violate the principle of energy conservation.
Next, they claim that this tyre technology will have better braking performance, but don't explain how. The only way you can improve braking performance in a tyre is by reducing rotational weight or increasing your friction coefficient/contact area, at the cost of higher rolling resistance.
Finally, they show a '50% better coast down' video, claiming this as evidence of higher efficiency. But it can only be because either the wheel has greater rotational momentum (because it's heavier) or because it has a lower friction coefficient. Both of these things are in conflict with their claim that they get better braking.
So in summary, I think the concept of a durable airless tyre for cars or mountainbikes is admirable, but I think the rest of their claims are just snake oil.
I use no-flat tubes in all my bike wheels now and these looked very interesting until they said carbon fiber rims.... no thanks.....
What about when they get filled with mud and spray all over you as your flying downhill?
What artist plays the music for the video of the MTB bike in action?
Not to bag the guy in the video, but having a real biker test it out would be nice. Actually show the tire from a five foot drop a down hiller would make and then show some speed like 30 MPH on a gravel road. I agree twist side to side would be bad and having a tire flex when you try to peddle uphill would suck. Also life expectancy from a tire from flexing would be nice to know. Please add a sidewall and different rims in the design. Interested keep trying.
greater efficiency stems from the spring action of the erw, which is an old, but potentially valuable, idea. at the point of contact, the spring compresses and decompresses, which has the effect of storing and returning the energy far better than any pneumatic tire could do.
the main problem is durability. the spring mechanism has to withstand all that action for a long time.
and the cost is still practically prohibitive.
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