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TPMS Tolerances

2K views 15 replies 10 participants last post by  0w40X1 
#1 ·
So, the past week I've periodically been in some pretty cold weather (teens deg F). And the TPMS sensor in various wheels, sometimes all 4, has alerted me that pressures were low. I presume this is due to the temp because when the car is in warmer environments, the warnings go away. I'll be verifying actual inflation pressures tomorrow. But, does anyone know how sensitive the TPMS is? For example, if the pressure goes down 1 psi, is that enough to trigger a warning? It would be quite annoying to have the TPMS alerts going off throughout the winter and I don't want to inflate the tires every time the temps drop. There must be some allowances for pressure variability due to outside temp changes.


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#3 ·
Our X1's up north come with FTM instead of TPMS.
Which technology is better I don't know. But the sensors seem more stable thus far.

I have TPMS in my truck and once we got below freezing the warnings went off. And have remained on for a week.
The X1 hasn't made a peep, even when I changed to Winter rims and rubber. Its the same circumference so that seems to make sense. However, I'm almost tempted to let 15 lbs out just to see if its working. :)
 
#4 ·
I got warnings a couple weeks ago when it hit about 40 degrees out. My tires were all down 6-7lbs. Luckily my compressor came the next day and I put them back to spec. I'm surprised how much they dropped as I use a digital checker every couple months to check them.
 
#5 · (Edited)
Just for grins, I set all tires with a temp gun when driving on a hot day on open road 75mph, but when they cooled off front drivers was 37 and front right 38.

The tpms went off as I turned left out of lot to leave home, so that condition was pretty sensitive.

So I put 1 pound in, and RESET the TPMS with the turn signal stalk.

I'm pretty sure the TPMS will give plenty of warning before causing damage.

Sorry I misread your concerns, but if you reset after filling cold, it shouldn't go off too easy.
 
#8 ·
This. Last week after being parked at the airport for a week my TPMS went off. First time in a year it did. Went to the gas station for air...I was number four in line for air! When I left, there were four behind me. So, it's the cold that sets it off. Fill it, reset it, no problem after that.
 
#9 · (Edited)
If you know your psi is about right you can catch cold morn, then, reset before driving.

The reset feature is a good idea especially since the recommended psi can be up to 38 front and 45 rears on my M Sport.

I don't carry much, and like 38 max all around.

That will get up to 42 just driving around easy.
 
#11 ·
This happened to me on Monday where I got a low tire warning. I was leaving Phoenix where the night got cool and X1 was parked outside hotel. I suspected it was cold temps, but swung into a BMW dealer to be sure before driving 380 miles home.

Can anyone recommend a good digital tire pressure gauge? Mine is broken and I'm looking for a new one, thanks.
 
#12 ·
The best gauge I ever bought was a $3.50 marked off every 2 psi.

I hold it on the stem to read psi, then, it goes to zero when I let off.

I can read it to 1 psi, and that's as close as I can feel even tracking it.

I think it's a fairly accurate dial gauge, and numbers are relative anyway.

It's consistent, and every day I track my car the necessary psi is different.

I've tried electronic digital, and I didn't trust the readings.
 
#13 ·
The TPMS only warns you of unsafe tire pressure not under inflated/over inflated tires. In reality we should check tire pressure a lot more than when the seasons change, and before long road trips. But practically nobody does that. Correcting your tire pressure will improve your mpg a lot. So if you notice mpg falling its time to correct the tire pressure.


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#14 ·
I'm wondering if my TPMS is even working since we don't get any feedback/status. I swapped to my winter wheels+tires yesterday, never touched the TPMS menu or anything at all, yet after 100 miles now it hasn't said there's a low tire pressure or reported it's not finding the summer wheel sensors. Go figure... I thought each TPMS sensor had a unique ID that had to be "learned" through a TPMS reset but my car is acting like I never switched tires. I however did get a low pressure warning a month ago, so the system was working then at least. Anyone know if this is normal? (Wheels/Tires were pre-installed from Tirerack)
 
#15 ·
It's been my experience that some tires just seem to act that way - the Yokohama tires on my wife's Rav4 just seem to drop 4-5 psi when the night time temps drop 20-25 degrees and trigger a tire pressure warning. They also seem to require small adjustments ever 2-3 months. The rims, valve stems, and tires have been checked for leaks but all is normal. Now the Contis on my '13 535xDrive just don't seem to budge an iota ... and I was a bit skeptical so I've checked it with a tire gauge (I use an analogue Accu-gage).
 
#16 ·
Normal tire driving temps seem to run about 110-120 deg f on a hot day, then cool off to nights low of say 60-70 deg in summer.

When winter comes the low can be say 30-40 deg f.

Thats 30 degs divided by 10 = 3 psi loss right there.

If you get psi straight on cold morn, then, that TPMS trouble should mostly stop until next winter.

I don't think my Pirelli P7 performance lost more than 1 or 2 psi in 6 months.
 
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