Winter Tire and False Flat Warning Indicator Question

[3forme]

I just bought a 2007 335i 6MT Sport (space grey with tan interior). Love the car.

However, with the cold weather coming on, I've started getting false flat tire warnings. The first time, I took it to the dealership service dept and they cleared it, but it has come back again. I've put air in to spec (they needed a little bit with the cooler weather) and have checked the pressure cold after two days of driving and everything is fine, but I cannot get the thing to reset per the owner's manual. Any tips?

Also, I just ordered winter tires (Bliz LM25s) but I don't believe they will coordinate with the car's pressure sensors. Is there a way to disable the tire pressure system during the winter? Or will these tires work with the sensors? Both the dealership and Tirerack as well as several friends all recommended the tire independent of one another.

Thanks all - my first post so be gentle!

[mryakan]

to reset, you press once till reset appears, then hold until a checkmark appears. I had to consult the manual since I couldn`t figure it out by just experimenting. If this keeps happening and using a gauge you confirm the pressure is still fine, you may have a faulty sensor. Take it in and tell them the tale.
For the winters, if you have the metal valve stems on your wheels, you need to either transfer them to your new wheels or buy new ones, but if you are mounting on the existing wheels, then all you need to do is reset the system after install.

[ziggypup]

I just bought a 2007 335i 6MT Sport (space grey with tan interior).

Also, I just ordered winter tires (Bliz LM25s) but I don't believe they will coordinate with the car's pressure sensors. Is there a way to disable the tire pressure system during the winter? Or will these tires work with the sensors? Both the dealership and Tirerack as well as several friends all recommended the tire independent of one another.

Thanks all - my first post so be gentle!

Once the winter temps stabilize and become more seasonable, your monitoring problems should stop.

Here in Ny we have been having 50/55 degree days with the nights getting down to freezing. That big temp difference from day to night will mess with the tire pressures.

I was just checking the forecast for Thanksgiving day. They are talking about it being close to 60 Degree's

I don't think you want to disable your tire pressure monitoring system. That kind of defeats the whole reason of having it.

[mryakan]

Once the winter temps stabilize and become more seasonable, your monitoring problems should stop.

Here in Ny we have been having 50/55 degree days with the nights getting down to freezing. That big temp difference from day to night will mess with the tire pressures.

I was just checking the forecast for Thanksgiving day. They are talking about it being close to 60 Degree's

I don't think you want to disable your tire pressure monitoring system. That kind of defeats the whole reason of having it.
Assuming a 1 psi drop per 10F, then even a 60F change in temps should not cause the sensors to report pressure drop. It takes a 10psi drop or 30% to trigger the warning. Just make sure you inflate the tires when cold (they do rise by 3-4 psi or more when they get hot after driving on them). Also keep a pressure gauge handy to measure the pressure when you get a warning and make sure all tires are at the same relative pressure (e.g. if you inflated the fronts to 32, they should be both at 28 or 34 or whatever, not one at 28 and one at 34 which would indicate a leak).

[Kernel Kurtz]

Assuming a 1 psi drop per 10F, then even a 60F change in temps should not cause the sensors to report pressure drop. It takes a 10psi drop or 30% to trigger the warning.

Anyone have a link to an explanation about how these systems work?

I'd always assumed the primary rationale was to watch for a tire whose rolling circumference was smaller than the rest, thus indicating pressure loss and an imminent flat tire. I would not have expected the system to tell me if all the tires gradually get smaller, but that's an added bonus if it does.

I added about 4 psi to all my tires today to compensate for the cold weather, but the relative pressures were still correct to begin with and I did not have to reset the system (or at least I don't think I have to - it has not complained).

I also assumed the system used the same wheel sensors as the ABS to accomplish these measurements. Whats this about valve stems.......?

[mryakan]

I also assumed the system used the same wheel sensors as the ABS to accomplish these measurements. Whats this about valve stems.......?

Check your manual for the explanation of TPMS vs FTM. I though FTM was offered in Canada while TPMS in the US, but I saw a 550 at the dealer with TPMS last time and I know older e90s come with FTM in the US, so who knows what the real deal is.

[3forme]

You guys rock. I needed to use the iDrive (pressing straight down) vs. the generic owner's manual instructions of working the computer position 1 and 2 on the turn signal. Man I feel silly.

Everything is square now. Fronts are both 32 and backs are both 36 and life is good.

[harryu]

how the tire pressure managment system works? Second, if I run a separate set of (cheap) rims in Winter will I screw up the system? Much Appreciated.

[808AWD325xi]

Also, I just ordered winter tires (Bliz LM25s) but I don't believe they will coordinate with the car's pressure sensors. Is there a way to disable the tire pressure system during the winter? Or will these tires work with the sensors? Both the dealership and Tirerack as well as several friends all recommended the tire independent of one another.

The Blizzak LM-25s are offered in a run-flat version as well. They are also available from BMW with a style 158 17" wheel.

The BMW part number for the tire/wheel combo is 36-11-0-421-680. It consists of 1 wheel with the tire pre-mounted and balanced (TPMS sensor and valve stems are included as well). MSRP is $652.50 each.

[ciramjo]

When switching to winter tires/rims with TPMS sensors installed, is any assistance from the dealer needed for the car to recognize the new sensors, or can that be done by the owner? I was told that in older systems a trip to the dealer is needed to get the car to respond to the new sensors.

Thanks
john

[sor]

On older cars the rotation/circumference of the tire was measured, but new standards in the US don't consider that to be accurate/safe enough, which is why we have the metal stems and sensors in the tires to actually measure the pressure.

Considering that you actually do lose a few PSI over time, mix that with lower temps and it's no surprise the sensors go off. If you reinflate and/or recalibrate and it still happens then you might just have a bad sensor, but I can't imagine they'd all go bad at the same time.

Its my impression that new TPMS sensors are configured the same way as when you put new tires on, you simply recalibrate the system and it works. I'm putting my OEM rims back on with winter tires and bought a new set of sensors for them, so I'll let you know how it works when I get them on. Should be either tomorrow or early next week.

[3forme]

Hmm. Tirerack guy told me if I had rubber stems (I do), I don't have sensors and the car does use the circumference technique. Once the tires are on, do the reset and off you go.

In fact, the owners manual describes both systems (2007 335i). I don't have a way to see the actual psi value, just a flat tire warning when it senses something askew (one tire rotating faster than the rest or faster than before?).

My prior car (2005 350Z) did have metal stems and would show the front and rear psi in absolute values.