This should be a puzzler. I know that the TPMS read the pessures from the 4 tires on the car, and will alert the driver if the pressure on one falls about 4 psi below the others. BUT....
If I'm carrying a spare (winter wheel/tire) with me in the car that has a TPMS in it too, then thee are 5 signals generated/interpreted. Does the logic of the system have enough smarts to compare all 5?
If I'm driving and get a flat (like happened in NC not too long ago) will the TPMS tell me one is low if 4 are still reading the same?
Interesting....
Anyone else doing this? Experiences?
Fig

 

I don't think the car would see it. My guess is the sensor readers are very close each specific corner. When I switched to non-runflats recently, I did not get TPMS sensors for my new wheels. My old wheel/tire set was in the back of the car intact with sensors installed and it still gave me a warning from the TPMS system on my way home.

 

I can't answer about the Mini specifically but my friend's Toyota pickup drove him nuts till he checked his spare.

Yep, it had a sensor and it was under inflated.

Hope this helps...

 

Unless you put the vehicle into program TPMS mode with the spare in the car, it would not be read by your onboard TPMS.

I'd sugest if you have the spare, dont worry about adding it to the vehicle's TPMS until its in service. You'd also want to get the 5th unused tire and wheel atleast 25ft from the vehicle for reprogramming. This eliminiates the possibility of reading the extra one.

You do have to drive to complete set up - so make sure to go back and get the 5th one!

As a matter of principal, check your spare's pressure every 6 months.

Alex