low tire pressure warning
 

I was ready to drive home and suddenly I'm confronted with the dreaded low tire pressure warning. I get the detailed window about what to do with RFTs (which I have) and gingerly make my way home to change clothes and check out the tires.

All the tires have the same reading and are well below standard. I call dealer and say did the significant drop in temps have anything to do with this? Yes. We've done 30 today. Come in and we'll get it right.

Is this going to happen every time there is a big drop in temps? Service said that a 30 degree drop (90 to 60) is enough to trigger this kind of behavior.

It isn't a problem with the sensors, it is a problem with your tire pressures. Be glad that you get an alert. I would keep a tire pressure gauge in the glovebox, so that you can quickly determine if you have a very low tire, or a marginally low set of tires.

Bottom line is, it is an alert system and not an inflation system.

Why not just put air into the tires so that they are at the correct pressure?

12p.m. almost 130F. 9p.m. almost 85F :) that is more than a 40 degree drop and im more than okay with all my BMWs !

I do keep a gage but wanted to change clothes before handling the filty stems and getting brake dust on me.

I previously had an "inferior" SUV that had a better tire monitor system than the X which is disappointing.

Here in OK, we have x number of days every year that the temps drop 30 to 40 degrees. I will now know better what to do, but it's still going to be a headache since I have to go around and inflate all the tires and then reset the monitor.

The service rep made it sound like something he had to do. I guess he was just trying to save me trouble, but had he simply explained what was involved it would have been easier to do it myself than drive out to the dealer.

I never experienced anything like this with my '04 4.4i and was completely caught off guard.

My guess is they were borderline inflated; thus the drop sent
the psi over the warning limit.

Pump 'em up "cold" and remember to check when serious autumn
rolls around. And, I'm with JCL: a 5 buck pencil tire gauge in the
glove box can tell you the tale. Couple that with a quick stop
at an air pump at the gas station and you won't have to tiptoe
home and/or to the stlr.
GL,mD

You may well be right about the psi prior to today but then again the dealer said they did the same job on over 30 units today.So he made it sound like the big te,p drop actually lowered the psi so that worries me with our weather pattern here.

The other comments I've tried to address in the last two responses that were probably posted about the same moment you hit "submit" for your post.

I have real time/real psi readout on my '02 Vette but I've
never seen that severe of a psi drop, induced by temp change.

I do see a few psi fall off from our occasional 75+ degree autumn
days vs our less than 30 deg nights, but I only see a few psi drop
even under those conditions. I also "gain" a lb or so, descending from
5,000 ft elev. to the "flats" down below, due to less atmospheric pressure
at this elev., I think.

Either its an edgy "system" or the tires were borderline in psi, or
it's another BMW low tech gizmo "monitoring" deal, imo.
GL,mD

True enough, but 85F is still much warmer than 60F. That is, I was being told that it was a big drop and it went from hot to cold. You went from off-the-scales to warm.