would having 17" alloys and tyres affect the tyre pressures a great amount or would they be the same as when you have the standard alloys?

I think there meant to be around 33psi on 17s not 100% sure tho

32 psi all round uladen on a octavia vrs with 17" alloys on autodata i just copied this

as a general rule usually between 30-35psi imo

i think mine are 36 psi atm but that was because i was doing a run to the airport with a boot full off luggage and a car full of people

normal is around 34 psi but i'm a mpg hunter so there always slightly higher