[Carl Morris]

I searched but everything seems to be about how to add or get rid of TPMS.

I have it, I like it so far, and I've run the tire pressures that it was at when I bought the car last January, low 30s all around. But it's been a little colder than usual the last couple of mornings and TPMS has complained about low pressure on one or more tires. I've checked them and they are normal considering the cold.

My question is, how does the TPMS work regarding its warning thresholds? Are they at a particular pressure, or are they at a pressure differential from when you last reset? In other words, could I just start running higher pressure all the time and never see this? Or will I still see it due to the cold pressure change from when they were last reset? I'd be perfectly happy to run 36+psi all the time if that will solve the problem. What happens if you reset at lower pressures and then add more pressure without resetting again...will it give overpressure warnings?

[Pete Schweaty]

http://www.tirerack.com/tires/tirete....jsp?techid=44

They alarm when the pressure in the tire drops more than 25% of the recommended cold tire inflation pressure. So the way I read it, if you over inflate the tire (dangerous, and not recommended) you will have some cushion. I wouldn't do it though, you will lose gas mileage, tread life, and the handling of the vehicle will be negatively effected.

[Bimmer This]

Tire pressure sensors aren't always accurate. Most will read about 3psi lower than actual tire pressure. For instance, if spec is 30psi, then the tire pressure sensor will read 27psi. The TPM system will turn on the light when you are +/- 5psi from the spec pressure of 30psi. So, it will illuminate when it is over 35psi or under 25psi, Get it?

If you have Nitrogen filled tires, that will also make a big difference as nitrogen is lighter then air. So, in cold weather nitrogen is similar to a helium filled balloon when you take it out in really cold weather. My suggestion is that you fill your tire pressures to about 35psi.

[llis]

In my experience, after about a mile of driving you can reset the TPMS and the warning will go away.

[Carl Morris]

Thanks everybody. My tire wear has been heavier toward the edges, so I need to start running more pressure anyway. So I think I will take the suggestion to run 35 or so. But can anyone for sure confirm or deny whether the target pressure for the TPMS system is always the same or if it changes after a reset? Sounds like everyone is saying it's probably always the same...

[Bimmer This]

tire pressures will always change depending on the weather. It will drop about 2-3psi during cold weather and raise about 2-3psi during hot weather. Like I said before, Nitrogen filled tires can read 5psi + under normal tire pressure especially in these cold weather days that we have had. You can do a reset, but it's not going to change the way the sensor reads. On all my cars, if the vehicle is equpped with TPMS, spec will call for 32psi. I will put 35psi in all four tires.

[Carl Morris]

So you're saying for sure that a reset does NOT change the target pressure to the current pressure?

[Bimmer This]

Originally Posted by Carl Morris

So you're saying for sure that a reset does NOT change the target pressure to the current pressure?

Nope. TPM sensors are made to "update" during certain driving conditions/mph. Unless you've rotated your tires or replaced a sensor, you shouldn't need to reset your system.

[Carl Morris]

OK, so run 35psi, it will all work like it's supposed to. Thanks...

[Bimmer This]

anytime