keep current width, or switch to 245/35 front and rear? (E46 330i)

[apenstaartje]

My current Bridgestone Potenzas (rear) are running low, so it's time for new one's. I've already set my mind on Goodyear F1 Asym, but...

I drive a E46 330i sedan. Currently the setup is 18" 225/40 front and 255/35 rear.

I'm thinking of switching to 245/35 front and rear. My question is: is there anybody who knows what the impact is on the ride? Better cornering balance? Less balance? Havier on the steering? More nervous? Smoother ride?

The reason is: the rear tires (255) are actually a bit to wide for the wheel. So the tire is a bit "curved to the outside" (sorry, dont know how to describe that in correct English. What i mean is: it's a bit like when there is too much air in the tyre).
And because of this, the tire is pretty worn down in the middle, but on the sides is a lot of tread left.

Also, switching to equal sizes front and rear, I hear the balance of the ride improves. And beause the front gets wider (and the rear just a bit smaller), there's more grip! At least... that's my theory

Any thoughts?

Thanks!