I went run flat back in 2004 on Honda odyssey (Michelin PAX system), and I will never go back. I will suffer for ride quality, but safety it brings beats down all negatives.

To OP - I am amazed you got 37k out your tires. I had same on my 2008 4.8, and they had to be changed at around 22k.

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His : 2013 X5 3.5d Deep Sea Blue/Black/Aluminum with ALL packages, 20" 214"s, running boards, Adaptive Drive, Spare Tire, BMW Apps
On Order : 2016 X3 3.5 MSport Silver/Mocha with DHP, CW, Prem, Tech, DA, Lighting

Hers : 2015 328xi MSport Silver/Red

Prior:
2008 X5 4.8
2011 X5 3.5d
2010 335 xDrive
2013 335 xDrive