[Makushr1]

I posted this under the wheel and tire section, but no one answered it, so I figured I may have better luck getting answers under this section...

I inflate my tires to the recommended pressure (says the inside of the door), front 32 psi, back 38 psi. At what pressure will the TPMS alert me for low pressure? I ask because it went off yesterday, and I checked my tires cold, both fronts were at 32, backs were at 37. I wouldnt think that 1 psi would set them off, or does it? Are mine really sensitive? Can I get the dealership to turn down my sensitivity?

Thanks in advance

[vegasspeed]

Do you use a digital gauge?

[Rando]

If I remember correctly it's a pretty big drop that triggers it -- either 25% or 33% or something like that. This is why you can only rely on it for a catastrophic pressure loss.

Alternatively, you could pump your pressures 25% higher than normal, reset the monitor there, and then lower the pressures. Then, even a slight drop will trigger the warning.

[mid-corner fun]

and BTW low PSI #s don't trigger an alert, only a PSI difference between left/right tires will. Not the brightest implementation IMO, as the exact PSI info per tire is available.

[lawdude]

Originally Posted by Rando

If I remember correctly it's a pretty big drop that triggers it -- either 25% or 33% or something like that. This is why you can only rely on it for a catastrophic pressure loss.

I've found that a tire with a slow leak will trigger notification at about 20 psi.

[hotrod182]

07's used wheel speed differential to trigger, the 08's have the tire pressure sensors in the wheels. Advantages to both. With a 07 whatever custom wheel you put on, the system will adapt. The 08's you have to transfer the TPM sensors.

[MaxL]

Originally Posted by PeterM1

and BTW low PSI #s don't trigger an alert, only a PSI difference between left/right tires will. Not the brightest implementation IMO, as the exact PSI info per tire is available.

That's not true for my car (335xi, 2007.5) - I once left it on an open parking lot on a cold night and few hours later it told me to pump up all four tyres (all four were highlighted in yellow on the tyre pressure screen). My TPMS seems to trigger the alert at 3.2-3.1 PSI (a drop from 3.6), which seems rather sensitive.

[e92phreak]

Mine seemed to alert when it went below 32psi...

[David1]

Originally Posted by hotrod182

07's used wheel speed differential to trigger, the 08's have the tire pressure sensors in the wheels. Advantages to both. With a 07 whatever custom wheel you put on, the system will adapt. The 08's you have to transfer the TPM sensors.

Not true, O7 coupes use the sensors.

[HighVoltage]

Originally Posted by David1

Not true, O7 coupes use the sensors.

My Aug 07 Sedan has them as well...

[rlb]

I have an 07 sedan w/ TPMS and my alert went off at 30.5 psi. My TPMS was originally set at 38 psi. I had a slow leak and it would consistently alert me after dropping from 38 to 30-31 psi.

[RiXst3r]

it goes off if you drop about 10 psi from your last reset point from what I have seen.

-Rick

[AndreyATC]

I think it alarms you @ 31PSI
This is what happened on my car
Difference was only 4PSI between other wheels

[RiXst3r]

Originally Posted by AndreyATC

I think it alarms you @ 31PSI
This is what happened on my car
Difference was only 4PSI between other wheels

Mine alarmed at 24 psi today, on all 4 tires. I had filled them up to 34psi hot, and reset, so it took a 10psi drop for me.

Seems to be different, might not be as simple as we think.

[jzchen]

Does anyone else find it strange that the manual says we should reset the TPMS every time we adjust the tire pressures? I found it strange. Maybe they just use that as the starting reference point and then when it drops a certain amount a warning is sent. Another car we have doesn't require me to do that. (I find it a pain since you have to drive the car to reset it!)

OP do you reset the system when you adjust the pressures? Maybe that will help. I'm not getting any low pressure alerts when the tire pressures are down only 1psi or so.

[AndreyATC]

Originally Posted by RiXst3r

Mine alarmed at 24 psi today, on all 4 tires. I had filled them up to 34psi hot, and reset, so it took a 10psi drop for me.

Seems to be different, might not be as simple as we think.

Interesting...
I wonder if TPMs are set to different levels of alarm?
Mine went off at 31 two times (very slow leak)
I gotta
Possibly it's different for different cars/MY?
I have E92 and it's MY2008 October 07 build

[mid-corner fun]

Originally Posted by AndreyATC

Interesting...
I wonder if TPMs are set to different levels of alarm?
Mine went off at 31 two times (very slow leak)
I gotta
Possibly it's different for different cars/MY?
I have E92 and it's MY2008 October 07 build

same here, E92 MY08 10/07 build, I've had TPMS alert on a 4 PSI drop on 1 tire (inflated to 32, measured after the alert at 28)

[Dan335i]

ON my 07 335i coupe inside the door panel,the recommended tire pressure is 32 fr and 35 rear.Yet everytime i read about this its noted that the pressure is 32fr and 38 rear by everyone.Is the coupes tire pressure different then say the sedans?

[zenmaster]

Originally Posted by PeterM1

same here, E92 MY08 10/07 build, I've had TPMS alert on a 4 PSI drop on 1 tire (inflated to 32, measured after the alert at 28)

I've had mine go off with a 3 to 4 PSI drop too. 03/07 build.

[kptaylor]

Wow, does anyone read the manual? The TPMS is not set up to throw an alert at a certain pressure. It's set to throw an alert when the pressure drops a certain amount from the pressure it was calibrated to initially! For example, if the initial tire pressure was 38 psi when it was set (or reset), then I believe it will throw an alert if it drops 3 psi from that point. It's been a while since I read my manual, so the 3 psi may not be accurate.

Mine alerted when I drove from Phoenix to Denver due to the temperature and altitude. Once I put air in the tires to get back to the appropriate pressures and reset the TPMS, it was good.

And what does this have to do with engines and tuning?

[AndreyATC]

Are you guys saying if i reset it at 38 it will alarm at 34-35?
It is 3-4psi drop
Hell no, not in my case
My rear tire drops about 4psi a week from 38, alarms me always at 31
My friend just got his first warning and it also was 31psi
I dont think 3-4psi drop is what sets the alarm.

I might be wrong, i did not read manual, and i have aftermarket wheels with TPMS purchased elsewhere (BMW OEM though), so this could have caused different reading?

BTW, this topic belongs to tire forum

[Richardo]

I had a slow leak in my LR tire recently. The alert came on (showing the leaking tire as yellow on the screen display while the rest were green) when it was 10 psi different from the others.