When you change a tyre or the tyre pressure on your Audi A3, you must confirm the change on the system.
Audi A3s with sound system
Before storing the new tyre pressures, check that the current pressures on all four wheels correspond to the specified values and adapt the pressures to the current load ►Link.
Select: SETUP button > control button 
Store tyre pressures > Store.
Store tyre pressures > Store.Audi A3s with MMI*
Before storing the new tyre pressures, check that the current pressures on all four wheels correspond to the specified values and adapt the pressures to the current load ►Link.
To do so, select: MENU button > Car > control button Systems* > Servicing & checks > Tyre pressure monitoring > Store tyre pressures.
Note
Do not store the tyre pressures if you are driving with snow chains.