[azzurribaggio]

I want to replace the wheels on my E90 325i with M135s, how will this affect the tire pressure sensor on the idrive? Will I still be able to tell if I'm losing tire pressure in my tires as I am now with my runflats?

[Squawks]

Car uses a system where it can determine loss of tire pressure through disparities in the rotational dynamics of each wheel. No sensors are used on the tire.

[spanna2000]

I understand that the tyre pressure is not measured. the computer monitors the wheel speed of rotation and records this - if the speed of rotation changes in relation to the other wheels then the tyre pressure warning will activate. Should be possible to do this with any size of tyre.

[azzurribaggio]

Originally Posted by spanna2000

I understand that the tyre pressure is not measured. the computer monitors the wheel speed of rotation and records this - if the speed of rotation changes in relation to the other wheels then the tyre pressure warning will activate. Should be possible to do this with any size of tyre.

OMG!!! We have one frickin AWESOME car!!!!! :rocks:

[Squawks]

azz - this method is actually inferior to the other systems utilized by other cars that can actually measure the tire pressure of each wheel and even let you know which tire(s) need to have their pressures adjusted.

In fact, if your BMW ran over a bed of nails and got 4 simultaneous flats, the flat tire sensor won't even signal.

[azzurribaggio]

Originally Posted by Squawks

azz - this method is actually inferior to the other systems utilized by other cars that can actually measure the tire pressure of each wheel and even let you know which tire(s) need to have their pressures adjusted.

In fact, if your BMW ran over a bed of nails and got 4 simultaneous flats, the flat tire sensor won't even signal.

OMG We have one $hitty car!!

[lux.sh]

since this topic is brought up, let me ask a newbie question.
I read the friggin manual and still couldn't understand. excuse my language barrier.

How are you supposed to use tire pressure sensor?
I use that knob on the left side to go to that tire pressure sensor thing.
According to my knownledge,
1. Stop your vehicle.
2. Use the knob and click on the tire pressure sensor option
3. drive???? what to do???

someone help me.

[alpinewhite3]

i cant find the tire pressure monitor screen in the i-drive?

[visor]

Originally Posted by lux.sh

since this topic is brought up, let me ask a newbie question.
I read the friggin manual and still couldn't understand. excuse my language barrier.

How are you supposed to use tire pressure sensor?
I use that knob on the left side to go to that tire pressure sensor thing.
According to my knownledge,
1. Stop your vehicle.
2. Use the knob and click on the tire pressure sensor option
3. drive???? what to do???

someone help me.

The steps you just described above are only for resetting the TPM after you've altered the tire pressures.

The TPM is on all the time, using the ABS sensors to detect changes in the difference of rotation speeds of the tires in a cross-wise fashion, ie. comparing the front-left with the rear-right. If there is a significant enough difference, you'll get a warning sign on the OBC display between the tach and speedo. You cannot shut it off.

[wuufer001]

I want to change the original Run-Flats to other type of tire which has no Run-Flats but i was wondering if the tire pressure sensor will still work. Please help me too.
Thanks

[KL2DC]

Originally Posted by wuufer001

I want to change the original Run-Flats to other type of tire which has no Run-Flats but i was wondering if the tire pressure sensor will still work. Please help me too.
Thanks

I don't see why it shouldn't...again our tire pressure monitoring is through the rotational speed (function of DSC)...

[hotsand5]

agent0986, you go to the main menu, then to information (middle option) then vehicle settings, and on the top bar, there should be FTM (flat tire monitor). When you get there, you will have the option to reset your tire pressure. You should only do this while your tires are cold as it will represent a more actual psi. If they are warm then the psi will read higer and the car might think you are loosing pressure.

--Here is another thing guys. When I got a slow leaking flat, I had like less than 15psi in my tire and rode around for about 15-20 minutes and no warning came on. Then I deflated the tire to 0 psi and within 1 min, the flat tire warning came on. So my question is...is our system only an actual FLAT tire monitor 0psi, or is it also a low tire pressure monitor as well, but it didn't look like it. Here are some photos.

[alpinewhite3]

Originally Posted by hotsand5

agent0986, you go to the main menu, then to information (middle option) then vehicle settings, and on the top bar, there should be FTM (flat tire monitor). When you get there, you will have the option to reset your tire pressure. You should only do this while your tires are cold as it will represent a more actual psi. If they are warm then the psi will read higer and the car might think you are loosing pressure.

--Here is another thing guys. When I got a slow leaking flat, I had like less than 15psi in my tire and rode around for about 15-20 minutes and no warning came on. Then I deflated the tire to 0 psi and within 1 min, the flat tire warning came on. So my question is...is our system only an actual FLAT tire monitor 0psi, or is it also a low tire pressure monitor as well, but it didn't look like it. Here are some photos.

thanks, found it.

[gmcwv]

Originally Posted by Squawks

azz - this method is actually inferior to the other systems utilized by other cars that can actually measure the tire pressure of each wheel and even let you know which tire(s) need to have their pressures adjusted.

In fact, if your BMW ran over a bed of nails and got 4 simultaneous flats, the flat tire sensor won't even signal.

And there is really only two sensors one in the front left and one in the rear right. I was looking around for them when I changed tires for the winter and saw only the two. So I would assume that those two can sense a flat tire in the ones without sensors, but it might just take a little longer, which is OK for run flats but not regular tires. Though I would think one knows if they have a flat with non RFT's

[visor]

Originally Posted by gmcwv

And there is really only two sensors one in the front left and one in the rear right. I was looking around for them when I changed tires for the winter and saw only the two. So I would assume that those two can sense a flat tire in the ones without sensors, but it might just take a little longer, which is OK for run flats but not regular tires. Though I would think one knows if they have a flat with non RFT's

That's not correct.

What you saw were most likely the brake pad wear sensors.

There is one ABS sensor for each wheel that are used to monitor wheelspeed, and hence used for TPM. The TPM algorithm only checks for changes in discrepancies in wheelspeed in a cross-wise fashion, ie. right-front vs. left-rear, and left-front vs. right-rear. I forget what the trigger threshold is before a warning is registered.

[ska///235i]

I recently changed my rims/tires and had two tires @ 35 psi and other two @ 37.5 psi....the FTM warning came on. I then fix all tires to 35 psi and reset the FTM, all went well

Now my question is...what if I needed to balance a new tire and have to use less psi to balance the other 3 tires, how can I bypass the FTM system? (Am I making any sense?)

[visor]

Originally Posted by ska

Now my question is...what if I needed to balance a new tire and have to use less psi to balance the other 3 tires, how can I bypass the FTM system? (Am I making any sense?)

Not understanding your question.

The TPM system only detects changes in the difference in wheelspeed, after you've given it a baseline reference when you reset the TPM in the OBC menu.

For example, let's say the front tires spin a 1000 revs/mile and the rears 1100 revs/mile, and the TPM is reset to this baseline as normal. If any tire loses pressure significantly enough to reduce the rotational circumference and increase the revs/mile out of the baseline normal spec, then the TPM alarm is triggered.

It is the deviation in the difference in wheelspeed from baseline norm that indicates a significant tire pressure loss.

So, after you've altered your tire pressures to your liking for handling/ride purposes, you have to give the TPM a baseline to work with by resetting the TPM.

[KL2DC]

Ska: sounds like you forgot to do the TPM initialization...

[gmcwv]

Originally Posted by visor

That's not correct.

What you saw were most likely the brake pad wear sensors.

There is one ABS sensor for each wheel that are used to monitor wheelspeed, and hence used for TPM. The TPM algorithm only checks for changes in discrepancies in wheelspeed in a cross-wise fashion, ie. right-front vs. left-rear, and left-front vs. right-rear. I forget what the trigger threshold is before a warning is registered.

Come to think of it, your right