Low tyre pressure indicator

[jp]

It lies!
Bought new tyres this morning but they only had 1 front tyre in stock.
As they all the tyres off I said it was ok to put one old tyre back on and I would get the 4th tomorrow.
So my dash goes red warning low pressure.
All the tyres are nice and hard so no low pressure.
So I assume the sensor must work off levels - the old tyre is possibly below 2mm.
just thought it was interestiing...

 

[turbopete]

i believe they work via the speed sensors for the ABS etc. the old tyre will be turning faster than the new ones (asits worn smaller) so the system thinks you have a soft tyre.

 

[JonnyCJ]

Reset it and it should compensate for the old tyre

 

[jp]

Got the fourth tyre and reset it.
Interesting point about resetting and compensating for the odd tyre, sadly too late to try.
I thought it was because the car was unbalanced...