you should be fine, my wheels are exactly: fronts 19" 8.5J et30 ( they are et35 but with 5mm spacers to clear UK brakes it is et30 ) tyres 235/35. rears 19" 9.5J et35 tyres 275/30. I will say that's the max for standard car. Maybe with different et you can go wider. Ah my car have standard suspension (reas) and it is not lowered.
I have done about 7k miles on them, that included 4k eurotrip (UK - France - Italy - Croatia - Slovenia - Austria - Poland - Germany - UK) many different roads (motorways, local roads, bumpy roads, lovely german autobahns) and all was ok.