I'm also happy with my V70a k90 on 225/45/17 but in the future I'd like to go for 245/40/17.
Now, there are several problems :
1) 225 go on my OEM denvers (7.5'' rim) wich is also the recommended width.
For the 245, the say the minimum would be 8'' but recommended is 8.5''.
8''x17 rims are common but 8.5''x17 not so much and more for the japanese cars.
Is it any danger on running a 245 R-compound on 8'' rim and a very heavy car ?
No, there isn't any danger.
You just won't get all of the benefit of the wider tyres if you fit them on a not-so-wide rim.
2) OEM denvers have an ET of 51.
Wich ET would be best for 245 in order to avoid fender rubbing on the outside and damper
rubbing on the inside ?
Don't want to mod the fenders and as you can see in the sig I have B16 + large sway-bars
so the car doesn't lean too much.
There's not much 'play' if you decide to run wider tyres. With 245 mm wide tyres and ET45
rims the wheel archs will rub I guess. With ET larger than 50 the tyres will touch the fat
Bilstein strut.
My personal conclusion of speaking to many many boys who tried out: you should make
your decision between ET48 and ET50 or even better go for smaller tyres.
I'd recommend 235/40 on a 8x18 BBS CH or a 8x18 Ultraleggera or Allegrita or if you prefer
17" then 235/40 R17 on a 8.0" or even 8.5" wide rim with an offset between ET45 and ET50.
On a side note, If I'll have to raise the car in order to avoid fender rubbing, I might be loosing
negative camber wich may take away some/all of the benefit of using larger tires !?!?
This depends on many factors, so I'm not keen enough to promise. If you go too wide and have
to lift too much the effect will be negative of course. But I guess lifting will not prevent for rubbing
on arch/tyre.