I know the debate about what tyres to use could rage for ages.. But I would like to ask advice about something else. Went into STS this morning to get a puncture repaired on my 2000 S6 4.2 V8. While they were doing it they checked the treads and said I have 3mm left on all tyres so would need some very soon. They also told me that because its quattro I had to change all 4 as there cant be more than 3mm difference between the front and rear as this causes diff problems and they can break. Is that rubbish? Or could I do 2 in a month then do 2 the next month or two without causing any harm to my diff. Was thinking of putting goodyears back on as they are on special offer at the moment with 25% off. Any comments or advice welcome.