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Self-inflating tire keeps the pressure up for cyclists

By

August 24, 2011

The PumpTire is a self-inflating bicycle tire, that uses the compressive effect of the tir...

The PumpTire is a self-inflating bicycle tire, that uses the compressive effect of the tire meeting the ground to force air into the inner tube

Image Gallery (7 images)

While it's nice to hear that Goodyear is developing self-inflating tires for cars, where does that leave bicycle riders? Still pumping, presumably? Well, not if they're running PumpTires on their steed. As its name implies, the PumpTire is designed to automatically pump air into the inner tube, using the compressive effect of the tire meeting the ground as it turns. Once the tube reaches the desired pressure, the pumping action ceases.

Invented by San Francisco's Benjamin Krempel, the prototype PumpTire system consists of a tire, an inner tube that clips into it, and an air valve. Air is drawn from the atmosphere through the one-way valve, which protrudes from the rim like a regular valve stem. Instead of going directly into the inner tube, however, the air goes into one end of a lumen, which is a small tube running along the center of the tire. As the tire rolls against the ground, the lumen is compressed, forcing air out of its other end and into a second valve - this one on the inner tube. The resulting absence of air in the lumen creates a vacuum effect, drawing more air in through the first valve.

That valve is able to sense when the proper pressure has been reached, at which point it stops drawing in air. Once the pressure has dropped again, due to the seepage that occurs with all tubes over time, the air intake resumes. In this way, if the product works as planned, cyclists need never have to check or "top up" their tires again.

A rending of the City Pro model of the PumpTire, with its user-adjustable air pressure val...

There are presently two versions of the PumpTire planned for the marketplace. The 26 x 1.5-inch City Cruiser is intended for casual cyclists, and will keep the pressure at a preset 65 psi. The 700c x 28 mm City Pro, on the other hand, is intended for more performance-oriented urban cyclists. Its maximum pressure is set manually by the user, and can range from 65 to 95 psi.

Both tires can also be manually inflated using a pump, and will be available with Presta or Shrader valves. While the valve appears to be rather large in the illustrations, it should reportedly be smaller by the time the product reaches stores.

PumpTires are intended to sell at a price of US$129.90 for a set of two City Cruisers, and $149.90 for a set of two City Pros. Interested parties can pre-order their tires now, through the company website.

The video below explains more about how the pumping mechanism works.

About the Author
Ben Coxworth 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
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17 Comments

Way too expensive. Not much of a selection, either. I won't buy a tire unless I know about its performance, like rolling resistance, puncture resistance, wear resistance, road grip, etc. That lumen worries me. What if you get a thorn in it? The tire has to be thrown out because there's no way to patch the lumen. How quickly will the lumen wear, considering how thin the rubber is on it? What about the stability of the tire? Tires with a center ridge were abandoned years ago because the ridge squirming made the tire unstable. Thanks, but I'll stick with my Schwalbes and Continentals.

Gadgeteer
24th August, 2011 @ 04:15 pm PDT

they should make them for car tires, would be cheaper than the TPMS out there

Bill Bennett
24th August, 2011 @ 09:05 pm PDT

Clever, but it fails the thorn test.

Slowburn
25th August, 2011 @ 02:08 am PDT

As the article states they are developing it for car tyres!

Secondly TPMS is/will be a legal requirement in most countries and will still be fitted as the primary reason is to avoid blowouts caused by faulty tyres, and you can guess how difficult it is reverse law!

livin_the_dream
25th August, 2011 @ 02:57 am PDT

This one does pass the thorn test...

http://www.treehugger.com/files/2005/12/nakano_air_hub.php

Bas Van Deursen
25th August, 2011 @ 05:34 am PDT

As the lumen tube is part of the ground contact patch, it will wear away as the tread wears. Slightly used tire == end of tire pumping.

Holly McBeal
25th August, 2011 @ 05:50 am PDT

Thanks much for your comments and enthusiasm! We have a list of FAQ on our Kickstarter site that gives an overview of the tires and answers common questions about the technology. You can view them here: http://www.kickstarter.com/projects/81926444/pumptire-self-inflating-bicycle-tire

If you have specific questions about the technology, ask our Engineers directly on our FB page: www.facebook.com/pumptire

Cheers!

PumpTire
25th August, 2011 @ 10:10 am PDT

what happens when the pump channel gets a puncture?

instantly the self pumping is useless

does the tire leak then?

can you even fix it?

can y ou still use a normal pump?

95 psi not enough for road tires

thing looks heavy and delicate

anyway

i don;t care

i can pump a LOT of tires for $130

wle

wle
25th August, 2011 @ 10:16 am PDT

$125 for an innertube? No thanks! I can go down to the local Walmart and get almost 50 innertubes for that price...and they have that green goop in them that automatically seals punctures. If I get the regular tubes (for my 26 in wheels) I can get almost 70 tubes for that price...

Plus, with this self pumping innertube, you will have to have the tire professionally balanced. I'm sure that with that Honkingly huge valve-stem it will throw that wheel into quite a bouncy ride!

Ed
25th August, 2011 @ 04:39 pm PDT

Ed: "$125 for an innertube? No thanks!"

What are you talking about? That's the price for two tires:

"PumpTires are intended to sell at a price of US$129.90 for a set of two City Cruisers, and $149.90 for a set of two City Pros."

Hopefully that also includes the associated valve mechanism. And, if they're good tires, that's a very reasonable price.

This is a fine invention. I don't know why people are so negative on it; the notion of a tire that tops itself up is appealing to me. I doubt the lumen will be that vulnerable and it's not like the tire won't still work if the lumen is punctured. And they say in the article that they intend to make the valve smaller. Chill out.

martin
26th August, 2011 @ 05:06 am PDT

I bet they won't be available in the size for old Schwinn 10-speeds. Love those old hand made fillet brazed indestructible Schwinns!

The tube on the outside looks very vulnerable to wear and punctures from Tribulus terrestris. AKA puncture weed, puncture vine or "goat heads".

Gregg Eshelman
26th August, 2011 @ 03:03 pm PDT

Seriously guys, the diagram is of the inner tube. The "lumen" will be inside the tire. Still worried? Get puncture resistant tires. Chill out, and quit being wrong on the internet.

David Desiccant Gardner II
27th August, 2011 @ 03:41 pm PDT

Photo 1 of the image gallery clearly shows the inflater tube "lumen" on the outside of the tire carcass. Looks like an ordinary inner tube to me.

As a matter of fact, the "lumen" rides off the tire carcass and into the side of the regulator valve which means you cannot use regular brakes with this wheel. You have to use a disc brake only.

Also where does it suck air from? The inlet appears to run up the other side of the tire but I have an idea it will suck in dust and water along with air.

This isn't a flat-proof tire, it's just a "top up" concept in case you don't have a pump with you or you have a tiny little air seep. That's what people mean when they say, doesn't pass the thorn test. The tire is still going to go flat if you hit a nail.

The lumen looks to be separate from the tire, which looks like it just has a central channel where the lumen runs. So supposedly if the lumen wears out you could peel it off and glue on a new one.

It's not a bad idea!

I got some "green tyres" and they are a genuine flat proof tire, that's because they are made of foam. But they have noticeably more rolling resistance, also the ride is somewhat "dead" and also sort of harsh. I think I paid less than this cost for a pair of Green Tyres and they don't use a tire valve whatsoever (funny when I point out to bike guys, "hey some joker stole my valve stems!" Ha ha.)

Grunchy
27th August, 2011 @ 09:40 pm PDT

DD Gardner: "Seriously guys, the diagram is of the inner tube."

No, it's a tire. Have a look at the picture of the tire at the top of the article; you can see the lumen running the center of the outside of tire. Have a look at the company web site; there are more pictures to make it even clearer.

It's a tire; it's not a tube.

Their FAQ says they will be making the lumen with kevlar are something similarly puncture proof. I agree that significant fear of puncture is not really a valid point of criticism.

martin
27th August, 2011 @ 11:43 pm PDT

Since about a half year ago I'm thinking about exactly the same idea: Putting air into a tire while it is rotating. The more it is deformed, the more air volume must be put inside, which would allow to use a tire with a small puncture too. Beside that the tire is got always the optimum pressure and thus the wear and tear would be optimum too. For cyclists the friction and comfort would be ideal too at all times.

I'm really happy that this solution might become - or already is - reality and I will definitely try two on the bicycle, I'm using for commuting. If you only count the time you will save for inflating this makes easily up for the 120 buck per piece. By exactly the same reason have I got an automatic lawn mower too and saved already several hours garden work and enjoying a much nicer lawn.

Newton2k1
28th August, 2011 @ 05:03 am PDT

amazing!!!

Evan Webb Stuart
29th August, 2011 @ 01:49 pm PDT

"$125 for an innertube? No thanks! I can go down to the local Walmart and get almost 50 innertubes for that price...and they have that green goop in them that automatically seals punctures. If I get the regular tubes (for my 26 in wheels) I can get almost 70 tubes for that price..."

This isn't an innertube, it's a tire. . . and would be not much over the price of a pair of high-end puncture resistant innertubes (about $80-$150 per pair for Michelin, Continental, etc.)

"Plus, with this self pumping innertube, you will have to have the tire professionally balanced. I'm sure that with that Honkingly huge valve-stem it will throw that wheel into quite a bouncy ride! "

They did say they were working on getting the valve size reduced. His FAQ did not indicate any wobbling and it would actually take quite a bit of weight to make a good road-bike wheel wobble significantly. Mine (DT Swiss) aren't perfectly balanced yet do not significantly balance at my riding speeds (less than 35mph, typical).

My only thing is that I pump mine up to about 105-110psi and these only go to 95 . . .

socalboomer
29th August, 2011 @ 03:46 pm PDT
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