This is an excellent idea. You wouldn't need that much pressure in the tank though. Even just 100 to 150 psi could keep the tire from getting low for a long time (unless you have a real leak). A lower pressure would be more convenient because you could fill it using a regular air compressor. A lower pressure would also be safer in the event of a malfunction.

BTW, thanks for reminding me, I need to check the pressure on my tires!

Thanks for your comment Dwane, I didn't think someone would answer me back that quick since some of these ideas on this site are dated back to 2004. My idea of having a high presser tank around the 1500 psi because of the relative tank size to air space of tire, this tank would be mounted in the center of the rime and made from the same thick material as the rime and withstand a high presser placed in it.

You can't really place the tank in the center of the rim because there are holes for the hub and lugs there. You could have a donut shaped tank around the rim between the lugs and the tire. It should go all the way around to avoid balance problems.

I still think 1500 psi is an unnecessary safety hazard. In an accident, it could explode. I suppose if the tank was very small it would be necessary to give it high pressure. I would recommend making the tank fairly large to avoid this.

By using regular compressor pressures, it would be very convenient to use. You would simply fill the tank exactly the same way as a regular tire, except that you wouldn't have to check the pressure. You just filling it to the max pressure that the compressor delivers and the regulator allows the appropriate amount of air into the tire. You would still need to top up the tank every year or so, but that's a lot less often than is normally required.

That's what I mint by placing the tank in the center of rim in the available cavity in the center, you are right and the tank would look like a donut. For the safety issue and the high presser , I do agree with you.

Now all this was though of that the tank is made when the rim is made, but what about making a tank that can be placed on just about any existing tire. Let's say a tank made from hard rubber that withhold the 150 psi and be placed on the rim from the inside with a regulator on it, the only problem I am thinking about this is how to inflate this tank without taking the tire of. I am thinking a hole must be made to the outside and that would take some considerable amount of precession to place it and seal it correctly.

While we're brainstorming, how about a tank that is shaped like a hubcap? It could attach in the usual hubcap fashion and connect via a short line to the wheel's original fill valve. One of the lugnuts could be a special retainer nut that ensures that it can't fall off. It could be filled through its own separate valve.

I think this is a great idea.