• Feb 27th 2008 at 4:27PM
  • 13
We all know that keeping your tires properly inflated will prolong their tread life, help you burn less fuel and increase your safety. But finding a working air hose when you're away from your garage is like trying to find a working clock in an early-80's Buick.
This is probably what led Coda Development, a Czech Republic company, to invent a new self-inflating tire. Sure, self-inflating tires aren't new, they've been around for years on commercial vehicles and even a few passenger vehicles . But most of those systems use compressed air to keep the tires inflated.

Coda's new system uses a peristaltic pump built into the tire to constantly maintain air pressure. You may have seen a peristaltic pump used in hospitals to deliver intravenous drugs to patients. It's basically a spinning wheel pressed against a liquid-filled tube. As the wheel turns, it pushes the tube's contents through one end and pulls more in the other. In our case, your car's wheel is the wheel and your air-filled tire the tube. A valve ensures that your tire's pressure is always constant. Theoretically, the peristaltic pump is much simpler and therefore more reliable than a compressor-based system. It's also potentially lighter, cheaper and doesn't require a power source. Sounds like a darn smart idea to us. Coda plans to display its system at the 2008 SAE World Congress in Detroit on April 14th through the 17th, so we'll see if it makes a splash there with auto industry engineers.

[Source: Coda]


SIT - the Self Inflating Tire system is a new invention of CODA DEVELOPMENT s.r.o., a company based in Prague, Czech Republic. The patented SIT solution offers a major advance in solving tire pressure concerns.

In the USA, 27% of passenger cars and 32% of light trucks and SUVs have at least one tire under-pressured by more than 25%. Under-inflated tires negatively impact safety, fuel economy and tire longevity. It is estimated that maintaining proper tire pressure would save the U.S. upwards of 1.24 billion gallons of fuel annually by improving gas mileage. In turn, this would eliminate about 250 lbs. of carbon dioxide emissions per vehicle every year.

The SIT System delivers key benefits. Besides benefiting drivers through elimination of unpopular pressure checks and dirty-handed inflating of tires, it helps to address the serious drawbacks of incorrect tire pressure. These include higher fuel consumption, shorter tire life, and accidents caused by under inflated tires. Plus it's a simple, inexpensive solution designed to be manufacturer friendly. Production costs for incorporating this component will increase only marginally compared to regular tires, while the surplus benefits the technology provides are significant.

SIT is an integral tire feature that uses atmospheric air to inflate the tire automatically when a vehicle is put in motion, compensating for natural loss of pressure and ensuring maintenance-free, constant tire pressure over the lifetime of the tire.

The SIT System is based on proven, highly reliable peristaltic pump principles. It integrates a tube chamber into the tire wall. As the tire turns against the road this chamber acts as a peristaltic pump, forcing more air into the tire until it reaches its desired pressure. Then a managing valve automatically stops further inflation. This simple solution ensures that all tires operate at optimal pressure at all times. Driving less than 1 mile compensates for typical leakage of 1 to 3% per month.

In comparison, currently available inflation systems use externally stored containers of compressed air or external compressors, resulting in higher costs, weight and more elaborate assembly. Plus, the containers ultimately have limited capacity and are not maintenance-free. SIT is a tire-integrated, self-operating component that uses atmospheric air to compensate for lost pressure as needed. SIT provides the most effective and inexpensive tire pressure control, while also being the most convenient solution for the end user - the driver. As a result of this development, people can drive their vehicles with complete peace of mind.

CODA DEVELOPMENT s.r.o. plans to develop the SIT System further into a proven production model in joint cooperation with established partners from the automotive and tire industries. In the coming months CODA DEVELOPMENT s.r.o. will initiate talks with potential partners in order to identify those best suited for introducing this new technology to the market.

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    • 1 Second Ago
      • 7 Years Ago
      I like your post, it's so nice. All parts of a car should be given proper maintenance to save money and time. Anyway, we don't have to worry regarding replacement, like nissan sentra parts, there are lots of auto shop store that has wide selection of car parts.
      • 7 Years Ago
      So what happens when you drive through a bit of water?

      Maybe not as much as this guy:
      But you get where I'm going with this.

      I don't doubt they've probably thought of this already, I'm just curious as to what they've come up with.

      Matto :)
      • 7 Years Ago
      As Frick pointed out, having a pressure release to control the pressure because the pump is running all the time seems inefficient. If my tires are properly inflated, do I want my car pushing four air pumps all the time, just to release the pressure out another hole? If you drive 1,000mi a month, you need this thing to inflate 1% per 1000mi, not 1% per mile. Sounds like a thousand times too much for most people.
      • 7 Years Ago
      I like your post, it's so nice. All parts of a car should be given proper maintenance to save money and time. Anyway, we don't have to worry regarding replacement, like nissan sentra parts, there are lots of auto shop store that has wide selection of car parts.
      • 7 Years Ago
      K.I.S.S. - If you've never heard it, it stands for "keep it simple, stupid". I really like this idea compared to the current electronic TMPS systems. We haven't even begun to see the headaches these sensors are going to leave in their wake - a mechanical system might be much simpler for the consumer (at least in terms of long-term maintenance).
      • 7 Years Ago
      Very interesting. Some thoughts:

      Is the "managing valve" built into the tire adjustable? If I want adjust my car's handling by adding a few extra psi in just the rear tires, how do I do that? If I try to add it manually, it seems the managing valve will simply release the excess pressure.

      If the managing valve fails - and the tire still has plenty of tread - can it be fixed/replaced independently of the rest of the tire? If not, it would seem that the managing valve could be a significant single source of failure.

      I like the approach. I've often though that current TPMS sensors should, in similar fashion, be motion powered instead of battery powered.

      Now if they can get this to work for the spare tire...
        • 7 Years Ago
        The "managing valve" could receive signals from an orbiting satellite. Users could upload their settings from their PC or iPhone.

        Of course in the US, the gov't would have final say over your settings, to ensure safety and optimal economy.
        • 7 Years Ago
        The same people who convinced the ninnies in DC that I need a TPMS would have you believe that you should not undertake any such adjustments, as this (obviously) might affect the behavior of the vehicle.
        A system also ads rolling resistance and weight to the tire/wheel package.
      • 7 Years Ago
      Working air hose? Why bother? I've used my bicycle pump for quite a while now with great success. No more wrestling with air hoses away from home!

      I've even filled a tire from 30 to 60 PSI (was a skinny spare, though) using just the tire hand pump. It took a few minutes, sure, but it was free and didn't require some machine that eats electricity or other fuel.
      • 7 Years Ago
      Interesting idea (way better than most TPMS systems) but I hope they addressed some of these issues in the design:

      1. It seems like there would be a lot of extra rolling resistance and wasted pumping that doesn't need to take place (once the tire is up to pressure... unless the pump stops when the release valve reaches the target pressure).

      2. Water. Won't this pump put water in your tires during the rainy season?

      3. It seems like you can't do proper front-back pressure adjustment to compensate for vehicle weight distribution and the different size contact patches it creates (unless you could adjust the pressure release valves - of course they would tell you to only have a professional do it - just like headlight alignment even though I've seen the pros screw it up just as often as DIYers). The pressure on your door sticker is the minimum. The pressure on the sidewall is the maximum. Neither are the optimum. Most front-heavy cars need some extra pressure up front.
        • 7 Years Ago
        * kballs

        I like your point 3!

        The pressure on your door sticker is the minimum. The pressure on the sidewall is the maximum. Neither are the optimum.

        All these years Ive been going stir crazy, so I usually try to keep pressure at the MAX hoping for better mileage & handling.

        If this product can handle -60C in the winter with the Eskimos, Im sold.

        Think of the domino effects of benefits:

        1. Better mileage
        2. Better handling
        3. Safety
        4. Tire Longevity
        5. Shorter stopping distances
        6. Emergency manouveres
        • 7 Years Ago
        Eric, you can also take a piece of wide chalk and run it across the tread then drive for 1/4 mile or so and see where most of the chalk has worn off.
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