Tire Size Question - E39 540i

[HardStep]

Hi again,
there have been many opics regarding tire sizes, but i didnt find a answer to my question.
Summer is here and i plan to get more attractive wheels than those factory 16" ones. Right now it has 225/55/16 but i'd like to make it look more aggressive, so desired width would be like 255 rear and 235 front, 17" diameter. Would like to have smooth comfortable ride, 18"s will be definitely too harsh on those roads i'm driving
Should i expect any negative side effects with these sizes? Will the 540i behave different than with stock sizes?
Should i go with any other tire sizes?
Thanks.

[sp0rky]

with larger wheels and tires you can expect many things
if the rims are heavier, you can expect a lack in acceleration and braking power.
You can expierence more pull in the steering wheel due to the wider tires wanting to follow the ruts in the road more, and because of a larger contact patch you can expect less-than-optimal gas mileage and a noticeable increase in road noise.

It shouldnt be too bad, though!

235/45/17 and 255/40/17 is whatcha want.

[Hownowevilcow]

The sizes listed by Sporky are stock for the sport model and shouldn't stress your hardware. Make sure the rims you select have the same offset as the factory model.
17s will make a nice change- post some pics when you do it!