[Adelbaran]

Hi people,

I recently had a flat tyre due to a nail puncture on my 2021 X1 Sdrive 18i. However I received NO warnings or lights on the dash to tell me if the car has detected lose of pressure!? There is a Flat Tyre Monitor system on this car but it doesn't show me any pressure readings or anything. It has a reset option and then just tell me it will reset as I drive.

As I didn't noticed the flat until the car was parked on the driveway, so I thought maybe the wheels needs to be spinning for it to work. So after I have gone and fixed the tyre, I reset the Flat Tyre Monitor in vehicle status and then purposely deflated one of my rear tyre to about 10psi and drove slowly (30-45km/hr) for about 1km, and it had nothing, no warning! Then I tried same on one of the front tyre and same, no warning light.

Is there something wrong that I need to take it in for warranty or I needed to drive longer and faster for it to defect the flat? Or does it only detect it when it's completely FLAT?

Also to my surprise that this car didn't have run flat tires? Don't all BMW have run flats so they don't have to give you a spare? The tyres that came with the car is 225/45R19 Goodyear Eagle F1 Asymmetric 3.

Anyone had similar experience?

[MJE60]

Originally Posted by Adelbaran

Hi people,

I recently had a flat tyre due to a nail puncture on my 2021 X1 Sdrive 18i. However I received NO warnings or lights on the dash to tell me if the car has detected lose of pressure!? There is a Flat Tyre Monitor system on this car but it doesn't show me any pressure readings or anything. It has a reset option and then just tell me it will reset as I drive.

As I didn't noticed the flat until the car was parked on the driveway, so I thought maybe the wheels needs to be spinning for it to work. So after I have gone and fixed the tyre, I reset the Flat Tyre Monitor in vehicle status and then purposely deflated one of my rear tyre to about 10psi and drove slowly (30-45km/hr) for about 1km, and it had nothing, no warning! Then I tried same on one of the front tyre and same, no warning light.

Is there something wrong that I need to take it in for warranty or I needed to drive longer and faster for it to defect the flat? Or does it only detect it when it's completely FLAT?

Also to my surprise that this car didn't have run flat tires? Don't all BMW have run flats so they don't have to give you a spare? The tyres that came with the car is 225/45R19 Goodyear Eagle F1 Asymmetric 3.

Anyone had similar experience?

Hi, welcome to the forum
If you have tyre pressure monitoring then it should provide warning when car is driven (where a tyre pressure drops by a material amount) , your test of reducing pressure to 10psi would have been more than necessary/enough of a drop so there may be a issue. The tyre does not need to be fully flat. I cannot advise on exactly how low a tyre needs to be but I recall my system triggered a warning when one tyre was 6 psi lower than normal.

Unfortunately specs change on cars and due to chip shortages some car build options may have been deleted in 2021/2022 so I would first do a VIN build check to see what build options are on your X1 (F48). In other words check your car actually has tyre pressure monitoring. For info, If your BMW has metal tyre valves (actual valve not just cap) then this is an indicator your wheel has a sensor fitted and has 2VB option.

There are two different tire/tyre pressure monitoring systems used by BMW. The BMW build codes are;

S265A TYRE PRESSURE CONTROL (TPC)
S2VBA TYRE PRESSURE CONTROL (TPC)

The 2VB option also called TPMS/RDCI is the one which uses sensors (metal tyre valve stems) in the wheel , the other system just uses tyre diameter and rotation and provides an estimate of tyre/tire inflation using the car traction control system (it has ordinary valve stems). Basically an under inflated tyre will have a smaller diameter/circumference and the abs sensors will see one tyre as consistently under-rotating which should then then triggers a low presssure warning. Cars with sensors actively monitor actual pressure and temperature and send info to car modules. BMW Cars sold in US & Europe usually have 2VB, the rest of the world usually does not.

A BMW VIN build check (vin decoder) involves using one of a number of internet sites which allow you to enter your car VIN number and see the build codes for your car. For example, a quick search gave sites such as

https://www.mdecoder.com/

If 2VB is not present you will never see tyre pressures shown. If S265 is fitted then I understand you get a low pressure warning but the display just shows green of red status against each tyre. If neither build code is showing then I expect no tyre pressure monitoring was fitted but as stated, specs change.

If you do have either 2VB or S265 build option then Your 10 psi test should have triggered a warning and I would ask the dealer do repair under warranty. Depending on market and model, it is possible for a BMW to have TPMS and non run flat tyres, my current car was sold with this spec. The TPMS detects relatively small pressure drops and so is a useful safety features even for ordinary tyres.

[Semi Retired]

I would suggest your test by reducing the pressure, speed and distance may not have been sufficient to trigger the sensors. If you are able to reset the tpms that would suggest it is fitted. As previously suggested not all BMW are fitted with run flats, this would be clearly visible on the side wall of the tyres. I have seen that many BMW models are now not fitted with run flats, only top end models. If in doubt check your Vin or contact your local dealer for help.

[Qsilver7]

Ditto on the two different tire monitoring systems.

If your iDrive screen says FLAT TYRE/TIRE MONITOR (or indicates RPA)...then you have the simpler system that uses the ABS wheel speed sensors to determine wheel rotation/circumference to determine if a wheel has lost pressure/inflation.

As tyre pressure drops, the radius of the wheel and with it the tyre rolling circumference will also decrease. The upshot is that the wheel speed of the affected tyre is increased. The RPA records the wheel speeds using the wheel-speed sensors of the Dynamic Stability Control (DSC). The Run Flat Indicator compares the speeds of the individual wheels and computes an average speed. In this way the RPA is able to detect a loss of tyre pressure.

The RPA detects a drop in pressure below about 30 % ± 10 % of the initial value. The RPA indicator and warning light indicates a drop in tyre pressure. The RPA will indicate this after just a short distance, as a rule after a few minutes, from a certain minimum speed (e.g. 25 km/h) up to the permissible top speed.

If you iDrive screen says TPMS or RDC (or something similar)...then you have the system that has the sensors inside the tires. But even if you have that system...it depends on what market you're in if the PSI & TEMP data appears. In some markets that feature has to be coded on.