Non run-flat security







Ironically the most serious puncture I ever had was in Pittsburgh three years ago when I drove the S65 back to visit them. The low pressure warning came on as I was on I70 westbound crossing into Ohio. Kept going while watching the tire pressure. The pressure was not dropping below the 33lb warning. Put air in the tire when I stopped for gas and all was well for the rest of the day, the tire held pressure as long as it was hot. I filled the tire to 46psi when I stopped for the night, there was a humongous nail in the tire. The tire pressure dropped about 7lb overnight when it cooled off. Showed 38lb cold in the morning, heated to 42 on the interstate and never changed the entire day so I drove it with the nail all the way home to SoCal. Since I had purchased the tires at the dealer they just put on two new rear tires, no cost, under their road hazard warranty.
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Don't overthink this one but just go with the tire of your choice. You'll be fine
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Calculated risk being without a spare and relying on a 'slime kit' and inflator. I just hope if I get a flat that doesn't respond to slime that I can find somebody nearby with a 245/45/19 tire on hand.



In hindsight, I think buying the full-size spare may have been unnecessary. My 222 was the first car I owned that didn't have a full-size spare and it freaked me out. I started running all these worst case scenarios in my head, so I scared myself into buying the spare. To his credit, the sales associate at Discount tried to talk me out of it. He pointed out that the spare would take up most of the trunk space (it does) and that road side assistance and the Tirefit kit, should be all I need. After driving 2 weeks with the spare and realizing how little room was left in the trunk, I decided to leave it in my garage and only use it for extended trips. And if I'm taking more that a bag or two, I find that I don't have room for the spare!
The Pirelli run flats that came with my S-class lasted 11K miles (unusual wear at the tire shoulder despite correct alignment). Michelin Pilot Sport AS 3+ has gone 22K miles with about 40% tread left with even wear across the entire tire.
There is something about the stiffness of the runflats that leads to premature wear at the shoulders.
It is highly unlikely you will encounter a blow-out. The most likely scenario is that you get a slow bleed from a nail or screw. And a portable 12V pump will probably inflate you enough to get yourself home even if you don't carry a spare.






