Asside from the poor ride and noise that most talk about are there any real advantages?

I do notice they take potholes much better than a regular ZR tire

 

It seems like the rims get the worst of the potholes from some of the pictures I've seen

 

It seems like the rims get the worst of the potholes from some of the pictures I've seen
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To be clear, in the USA, do non-sport package 545's come with run flats?

 

You don't have to stop to change the wheel... Seems like a pretty big advantage Especially if it's pouring of rain!

No spare tyre in the boot taking up room and weight...

 

The biggest advantage of the run flats is the convenience of not stopping on the highway or the middle of nowhere (Safety) and putting the dougnut on the moment you get a flat.
With that comes certain safety of not having a complete blow out at 100+ mph and being able to stop without the tire rolling off your rim
With that comes a bomus of putting around to a dealer or warm garage to put your doughnut on.
Extra Bonus - if you have to run over police spikes - you can keep on going

Disadvantages:

- stiff side walls - bumpy ride, harder hits, from harder hits- suspension and rims can suffer - there were some reports of broken rims from hitting potholes with runflats

- harder rubber compound - not as sticky, not as flexible, can not resist heat cycling like non run flats = less performance for the money

- noisy and don't last as long (probably becaus of compound)

- impossible to repair even small punctures
- expensive to replace

 

Pros: Dont have to change the wheel is you have a flat tire, and most importantly, if you get carjacked they cant slash your tires. So there is a safety advantage.

Cons: As mentioned above, noise and extremely harsh ride.

 

On the plus side:
Safety
Convenience
Protection from curb rash
Unbelievable handling with two blown on the same side
Maintains a good semblance of wheel integrity when wheels fail
Maintains air pressure reliably when mounted on BMW wheels

On the negative side:
Cost
Worrying about all of the noise my peers experience that I may have to listen to one day.

 

Pro: During a police chase, you can drive right over the spike strips before they nail you with the roadblock...

 

If in need/want to change out of my RunFlat tires, can i change them two at time or do i HAVE to do all four at once? (I know my front tires are diff size than the rear)

Teriyaki

 

At high speed, the run flats feel unstable, creating a "shimmy" feel. I have heard some describe this as tramlining, though I am not sure that is accurate.

I now have on Michelin Alpina winter tires, and they feel much more stable at speed.