If the
If the Toyota Sienna is AWD, or 4WD, then the tires have to have fairly even wear on all four tires. Otherwise the miss-matched tires might damage the transfer case, or so the story goes they say.
One of my cousins regularly runs his AWD Subaru with miss-matched tires. There has been no damage so far. At least as far as we can tell anyway. Yet, no tire shop would install miss-matched tires on the Subaru.
Depends where you are when the tire goes flat. In the good old days you’d put on the spare, or the cheap car days you put on the donut. The purpose of run-flats is you have almost the nominal range of a donut so you don’t have to park by the side of the road or ruin the rim getting to a reasonable place to stop. Around town, you might be able to park somewhere safe within a block or three, but on a road trip? Good luck finding a place with a suitable replacement in stock in a small town or the middle of the countryside.
I’ve seen discussions that certain spare donuts for cheaper cars (Toyota? Nissan?) are the right size and shape for the high end cars; or like I mentioned above, modernspare.com is something I’ll probably buy a donut from instead.
Well, in that case I believe it’s due to the different sized tires causing wear on the limited slip components of the car. In mine, that’s a viscous coupling, so it wears out the friction modifier and it eventually just acts like an open diff. Either way, you probably won’t notice anything worn out until it starts spinning the tires.
I believe the safety factor alone far outweighs the minor nitpicks naysayers have with runflats. Maybe they had some early models or whatever, but they don’t consider what “could” happen in a fairly common traffic scenario. I suspect the industry will evolve to an all runflat ecosystem, at least in the commercial/OTR and passenger/retail sectors, in years to come.
Both my new cars (BMW, Tesla) have pressure monitors. So theoretically, a sidewall blow-out as a result of running very low pressure until the sidewall overheats and fails should be preventable, if you pay attention to your vehicle. I suppose some road hazards do result in rapid failure of the tire, but generally it’s the slow leaks. One of my tire problems, it was a very slow leak, and I could fill the tire (which I did) several times every hour or so to get to the dealership.
the basic problem is still finding a tire when on an extended trip. More and more, tires for higher end cars seem to be specialty items that need to be ordered, not in stock. I assume a Toyota or Honda or Ford F150 would not have this problem.