There seems to be tire issues with my Model S on 21" whenever the air temperature (weather) drops rapidly: In January the day when it dropped to 3 degrees, TPMS alerted low pressure (~1.7 bar) on my front left tire. Checked it out at a tire shop and said the sealing around the monitor inside the tire wasn't fitted very well and when it gets cold and shrinks a bit, air goes out. Tonight when I drove TPMS alerted me for the rear right tire @2.4 bar. Haven't checked it out it yet but wondering if any of you have encountered similar issues. And may I ask what pressure does are your 21" tires running on? Thanks!