Apologies now.. Tyre sizes audi tt mk3

[NitrousRuss]

As said in the title Apologies if this has been bought up before... Just bought my audi tt mk 3 and it's got 255/30/20 pzeros on it, looking for different tyres for two reasons, first under steer on on a couple of wet roundabouts, also the really low profile sidewall could I run a 265/ 275 with out to much issue

Many thanks
Russell