on board tire pressure monitor.. ???

[oduli81]

how accurate is your on board tire pressure monitor. I am getting a different reading on the compressor and on the bmw computer. its off about 2psi.

the recommended psi is 32, is it on cold or warm that recommendation??. reason I ask, the weather in NYC is getting hot and 32psi before driving turns to 34 plus at 100 degrees after an hour on the highway.

[zamboni]

I believed is always based on cold temp when measured.

[BzsBimmer]

Cold. Air expands when heated.
When measuring when hot, reduce pressure to desired temps (ie during track events) and then increase back to required psi when cold.

[ChuMpion3]

Cold, sitting temp. Expansion above that is fine. Some guys even start closer to 34.

[oduli81]

Originally Posted by ChuMpion3

Cold, sitting temp. Expansion above that is fine. Some guys even start closer to 34.

thanks..

[Fat Goose]

What are you guys setting for cold psi temps? I remember my last bmw, there was a psi difference between the fronts and rears, and when expected to be 100+ mph

[NSX2M4]

I set mine for 31 cold. Once hot they're either perfect 32 or 33.
It seems as though when they're anything over that, ride quality is much more firm.
Could just just be a placebo affect but I like em right at 31 cold.

[behindthen0thing]

I go for 27 cold and on track they end up about 34-36

[RickFLM4]

I go for 30 cold.

[dvq]

TPMS is always off 2-3 psi for me at the beginning and end of every track session for me -- I've measured with multiple gauges, those always are within half a psi of each other, TPMS reports 2-3psi low.

[AMG]

When people talk about PSI it's usually cold unless otherwise specified. I go for 31/33 although I don't track so +/- 1 is negligible to me.

32 that turns to 34 is fine. Sometimes when my car comes back from the dealers it's like 38/40 which is just too much imo.

[oduli81]

Originally Posted by AMG

When people talk about PSI it's usually cold unless otherwise specified. I go for 31/33 although I don't track so +/- 1 is negligible to me.

32 that turns to 34 is fine. Sometimes when my car comes back from the dealers it's like 38/40 which is just too much imo.

exactly what I am going to do. seems to be right. do you trust the on board computer?

[Aaaaaaaaa]

Just a word of caution, a difference of 0.5 PSI between rear tires can have disastrous consequences

[RickFLM4]

Originally Posted by oduli81

exactly what I am going to do. seems to be right. do you trust the on board computer?

Always use a gauge. TPMS is an ok safety feature in case pressure drops to alert you, but otherwise, I check every couple of weeks or so with a gauge.

[secretariat]

on board tire pressure monitor.. ???
how accurate is your on board tire pressure monitor. I am getting a different reading on the compressor and on the bmw computer. its off about 2psi.

the recommended psi is 32, is it on cold or warm that recommendation??. reason I ask, the weather in NYC is getting hot and 32psi before driving turns to 34 plus at 100 degrees after an hour on the highway.

Usually the 32 turns into a much higher PSI after driving in a 100 degree weather for an hour. Mine usually will hit 38 to 39 in that temp. and time frame.