I echo everything Ginger has said BUT
If your not bothered about the speedo reading high, so your actually going a bit slower
& you've got standard ridehight then I think you'll be fine with the tyres you have suggested.
Just don't go any bigger.
As standard the 406 has a lot of wheelarch clearance both in ride height & width.
My own estate has coupe starfish on with 205/55/16 tyres , the coupe wheels are less offset so stick out more
& I have lowered it 40mm & tow a caravan fully laden down Welsh & Cornish lanes & have never had ANY issues
The reason I mentioned the coupe offset difference is because it's a greater difference than your tyre choice's
You can also get longer/hd springs to rise the rideheight a bit more

2002 110 HDi estate, Rapier in monaco blue! ( found quite a bit more power

) SOLD I've sorted the airbag light
1998 3.0 V6 SE coupe in Diablo Red ( my baby ) sold
2006 206 1.4 16v sport in Aegean blue ( wife's shopping trolley

)
2006 BMW e61 535d m-sport

run's for cover
