Bicycles

Self-inflating tire keeps the pressure up for cyclists

Self-inflating tire keeps the ...
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
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
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A rending of the City Cruiser model of the PumpTire, with its preset air pressure valve
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A rending of the City Cruiser model of the PumpTire, with its preset air pressure valve
A rending of the City Cruiser model of the PumpTire
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A rending of the City Cruiser model of the PumpTire
A rending of the City Pro model of the PumpTire, with its user-adjustable air pressure valve
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A rending of the City Pro model of the PumpTire, with its user-adjustable air pressure valve
A rending of the City Pro model of the PumpTire
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A rending of the City Pro model of the PumpTire
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
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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
A prototype PumpTire
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A prototype PumpTire
A prototype PumpTire being tested
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A prototype PumpTire being tested
View 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 valve
A rending of the City Pro model of the PumpTire, with its user-adjustable air pressure valve

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.

View gallery - 7 images
17 comments
Gadgeteer
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.
Bill Bennett
they should make them for car tires, would be cheaper than the TPMS out there
Slowburn
Clever, but it fails the thorn test.
livin_the_dream
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!
Bas Deursen
This one does pass the thorn test... http://www.treehugger.com/files/2005/12/nakano_air_hub.php
Holly McBeal
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.
PumpTire
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!
wle
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
Ed
$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!
martin
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.