What is the Tyre pressure drop value ie 1 / 2 / 5 Psi, for the dash low pressure alarm to come on ?

Pretty random, but a 3psi drop might trigger the TPMS.

The tyre type can make a difference i find. XL (reinforced sidewall tyres might need to be a bit lower than the pressure was set at to get a warning.)

 

Try it yourself maybe, set your tyre pressures, reset the TPMS,  then after a while drop a tyre by 2 psi at a time.

There are no pressure sensors for the TPMS system so it can take a 25% drop or more to trigger an alarm.

 

 

There is more info here, you have the indirect system: https://www.my-gti.com/321/volkswagen-tyre-pressure-monitoring-system-tpms

Per @langers2k on the Oct 2 it is based on wheel rotation and not directly on tyre pressure so hard to equate other than trial and error by dropping pressure and seeing when it kicks in. It will depend on wheel size, tyre size and maybe even brand subject to deformation from reduced pressure affecting rolling distance.

 

You need to resent the tpms fairly frequently. Refuelling is a good opp.

I have indirect TPMS in my car and one of my tyres recently picked up a slow puncture thanks to a nail. I have no idea when the puncture happened but when I checked the pressures the affected tyre was at 1.8 bar (a 15% drop from the normal 2.1 bar) and that was after I had driven 20 miles with the pressure warning on the dash. Even with that tyre 15% lower than normal I could not tell by eye which tyre was deflating without putting a pressure gauge on all four. At first I thought it was a false warning from the TPMS but alas it was not.

 

 

 

Edited 23 May, 20206 yr by slow_nick

Cheers. Was a nail in the end.

@wd20

The thing is you never mentioned in the OP that you had a warning.

 

So how much had the pressure dropped from the pressure when you set the TPMS to when you got a warning?

Edited 28 May, 20206 yr by Roottootemblowinootsoot

I would estimate that the tyre lost app 10 psi before the TPMS activated. Certainly a good safety measure

The cheapest / simplest system that was needed for cars with Runflat tyres.  BMW / BMW MINI drivers were not noticing they had a flat tyre.

(or not flat as the case might of been.)