AlanSubie4Life
Efficiency Obsessed Member
If the tires are inflated using a race gauge and set at 42 PSI at 6,000 feet the Tesla thinks the tires are at 39 PSI and throws an alarm
This is what he said. It seems like exactly what one would expect if the TPMS thought it was at sea level (it has no idea where it is or what the atmospheric pressure is).
I thought he said that the pressure the TPMS was showing varied with altitude not that he couldn't put the right amount in at altitude
I am not sure what that means, exactly. It's a confusing issue to talk about, I understand, and in Deflategate it even tripped up some pretty accomplished scientists. It might trip me up here; it's pretty easy to get things backwards. I am not sure what "the pressure the TPMS was showing varied with altitude" means. If the claims are correct, the way it will behave if you magically transport a wheel instantly from Denver to sea level, is that the TPMS will NOT display a change in pressure in the car. That is because there is the same amount (number of molecules) of air in the tire as when you started, and it (the car computer) is subtracting a constant 14.7PSI from the absolute pressure, so it will display the same number in the car (39PSI according to my earlier example).
However, the tires will read too high pressure when he moves to sea level and will actually be overinflated.
NO. The tires have less air in them, so the gauge pressure will read lower at sea level than in Denver (for the above magically transported tire). Think of transporting an empty water bottle to sea level - it gets crushed under the weight of the air. Similarly the tire will become flatter. (As you would expect for a tire that is at 39PSI according to the TPMS at sea level.)
Yet somehow other manufacturers have managed to fix this without "cheating somehow".
If you're talking about gauge pressure changes with elevation, nobody has fixed that. If you want the TPMS to report the approximately correct gauge pressure, yes, the other manufacturers have figured that out.
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