[AdamN52]

I drive a 2007 328xi, and after putting on snow tires/rims a couple of weeks ago I am having the flat tire warning light come on every few days.
Note I have the FTM, not TPMS.

The snows are 205/55/r16 (same as stock).

When it happens I typically pull over just to make sure it's ok and the tires are not flat or even low.
They are all filled to the same pressure as well. I've just been resetting it using iDrive, but it seems to always come back after a few days.

Is there a reason this keeps happening? How does the FTM sense a flat, by sensing a difference in wheel speed or something?

I've never had it happen with my summer tires.

Thanks for any help!

[AdamN52]

Anyone at all have any insight? It now happens daily.

What could I try/check? Is there a wheels-peed or abs sensor i could have disturbed while swapping to my winter tires?

[BashShah]

Did you reset your FTM?
Do you have I drive?

DN

[AdamN52]

Originally Posted by DarkNemesis

Did you reset your FTM?
Do you have I drive?

DN

Yeah, I've reset it through iDrive each time. Still comes back though

[iDriveanXi]

I'm pretty sure FTM works by wheel speed. If a tire is low or flat it'll rotate at a different rate than properly inflated tires and set the indicator off. Maybe you have a wheel speed sensor going bad?

[AdamN52]

Originally Posted by iDriveanXi

I'm pretty sure FTM works by wheel speed. If a tire is low or flat it'll rotate at a different rate than properly inflated tires and set the indicator off. Maybe you have a wheel speed sensor going bad?

That's possible I suppose - if it keeps up I guess I'll take it to an indy and see if they can figure it out.

[olivojoe]

Could it just be that the tire pressure is low due to the cold weather?

Remeber from chemistry.......PV=nRT

As Temperature decreases, so must the Pressure.

Not sure if this is too relevant seeing as how you have FTM not TPMS, but take it fwiw.

[AdamN52]

Originally Posted by olivojoe

Could it just be that the tire pressure is low due to the cold weather?

Remeber from chemistry.......PV=nRT

As Temperature decreases, so must the Pressure.

Not sure if this is too relevant seeing as how you have FTM not TPMS, but take it fwiw.

Good point, although I'm fairly meticulous with keeping my pressures to spec. Even more so with this light coming on all the time. I keep them around 34psi cold, and they've been holding pressure just fine. I usually check them once every week or two, but I've been checking them every day or two with this issue.

Still having this warning come up daily now

[AdamN52]

Originally Posted by SSW

Most likely a bad sensor. Any tire shop should be able to check out the sensors w/o taking the tires/wheels off the car by using a TPMS RF tester.

There are no TPMS sensors - this car has the Flat Tire Monitor (FTM) system.

It's possible a wheelspeed/abs sensor is faulty, but I think that would throw a CEL, which hasn't happened.

[AdamN52]

Update: didn't do anything and it hasn't happened in 2-3 days. Here's hoping it has permanently resolved itself!

[Tom K.]

Originally Posted by AdamN52

Update: didn't do anything and it hasn't happened in 2-3 days. Here's hoping it has permanently resolved itself!

Sometimes, even thinking about taking it in can solve a problem. Sort of like how some maladies disappear once you have made a doctor's appointment.

Hopefully, the problem remains resolved!

Tom

[AdamN52]

Originally Posted by Tom K.

Sometimes, even thinking about taking it in can solve a problem. Sort of like how some maladies disappear once you have made a doctor's appointment.

Hopefully, the problem remains resolved!

Tom

Haha, yeah I suspect maybe I scared it into hiding for a bit. It's still happening sporadically. It must have something to do with the winter setup I've put on.

Maybe there's an imbalance in one tire or something that is causing it to sense a larger drag on one wheel.

I don't feel or see anything out of place, so I'll just keep resetting it for now.