I've run into an issue, and I know I am not alone in this matter.  My wife and I bought a 2007 Nissan Quest 3.5SE W/Navigation, and in doing so the Michelin PAX tire system was included.  Well, we have approached 40k miles on the vehicle, and let me tell you that we absolutely love the vehicle.  They sky roof and dual dvd screens are great for the kids, and the Navigation is perfect for my wife (who drives this van daily).  

The problem that we are running into is we need to replace the tires.  Well you would expect about a $600 to $800 for a good set, but not with this.  To replace the PAX system, is going to run about $1300+, just to change the tires.  Furthermore, there is only a handful of locations that can actually do it, and they are all at least 30 miles from my home.  Needless to say we are not pleased.  When we were purchasing the vehicle, the sales rep was touting how excellent the tire system is and that we would enjoy its comfort and reliability.  Well, we have about 37k on the van and the tires are shot, they have worn evenly, and still produce an incredibly smooth ride, but they will no longer pass inspection, and will probably last another 2 months maximum.

Steps we have tried to take:

1. We called Nissan, and they are no help at all.  They only thing they are saying they can do is file a complaint and place it in the computer system.  Mind you, we could replace the set of tires and rims to a standard set, but they say compatibility and other things come into play, and it could make the vehicle ride incorrectly or be unsafe.  

2. Called Michelin, and there is nothing that they can do because it would be the dealer or Nissan we would need to speak to.  So we are getting the run around.

After doing this, I have scanned the web for any information I could find and come to find out, this is a wide spread problem and it seems as though they have discontinued the PAX system, though I cannot confirm this.   Michelin also stated to us that all Nissan dealers are not certified to handle the replacement of these tires, yet in the manual for the vehicle it states that you need to take the vehicle to the nearest Nissan dealership if you get a flat.  But once you get there, they wont be able to do anything anyway.  So all around this is a problem.  Michelin states that you can drive 125 miles on a flat with these, but what if you are on a road trip, and you get a flat.  You are hundreds of miles from home, and no dealership around can fix the tire, so you are stuck at a custom tire shop maybe for days, waiting for them to get a tire.  This is all betting on whether or not you can actually find a place that can do it.  Nissan did not include a spare, since you "technically" you don't need one.  

We ended up finding a location about an hour away that can do the tires for $310 each.  Not awful, but for a cost this high you would expect to get top of the line tires that have 80k plus warranties, not these though.  With the PAX you get 2 years or 50% tread wear, and after all my reading, these tires are lasting most people about 20k miles, so right here we are the lucky ones since we have made it almost 40k.  I'm sorry, but $1250 for 20k tires is not worth it and my wife and I are going to continue to fight this.

We have contacted a lawyer, and they have asked us to represent Massachussetts in a litigation that is being brought to Nissan.  A brief explanation can be found here.  Please contact them if you are having the same problem.  Something needs to be done here, because $1200+ every 18 to 24 months is not acceptable.  I would be better off replacing the rims and tires for $1500, and then replace the tires on those for ~$600 every 60k miles.  I don't want to hurt my vehicle either and I am not sure how the internal PAX computer system would handle regular wheels and tires with Tire Pressure Monitoring Sensors (TPMS).  I have read that they work just fine, but not sure what happens if you get a flat on regular tires.  You would then need a spare anyway, which was not included with the vehicle.  So you would have to get it towed.  Let me know if you have experienced the same problem, or if you have a good solution.  I will be taking it to replace the tires within the next two weeks, it's a necessity at this point.